Publications by authors named "Shuangyin Wang"

104 Publications

High-Entropy Alloys for Electrocatalysis: Design, Characterization, and Applications.

Small 2021 Nov 5:e2104339. Epub 2021 Nov 5.

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.

High-entropy alloys (HEAs) are expected to function well as electrocatalytic materials, owing to their widely adjustable composition and unique physical and chemical properties. Recently, HEA catalysts are extensively studied in the field of electrocatalysis; this motivated the authors to investigate the relationship between the structure and composition of HEAs and their electrocatalytic performance. In this review, the latest advances in HEA electrocatalysts are systematically summarized, with special focus on nitrogen fixation, the carbon cycle, water splitting, and fuel cells; in addition, by combining this with the characterization and analysis of HEA microstructures, rational design strategies for optimizing HEA electrocatalysts, including controllable preparation, component regulation, strain engineering, defect engineering, and theoretical prediction are proposed. Moreover, the existing issues and future trends of HEAs are predicted, which will help further develop these high-entropy materials.
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http://dx.doi.org/10.1002/smll.202104339DOI Listing
November 2021

Tailoring Competitive Adsorption Sites by Oxygen-Vacancy on Cobalt Oxides to Enhance the Electrooxidation of Biomass.

Adv Mater 2021 Oct 16:e2107185. Epub 2021 Oct 16.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, Advanced Catalytic Engineering Research Center of the Ministry of Education, the National Supercomputer Centers in Changsha, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.

The electrooxidation of 5-hydroxymethylfurfural (HMF) offers a promising green route to attain high-value chemicals from biomass. The HMF electrooxidation reaction (HMFOR) is a complicated process involving the combined adsorption and coupling of organic molecules and OH on the electrode surface. An in-depth understanding of these adsorption sites and reaction processes on electrocatalysts is fundamentally important. Herein, the adsorption behavior of HMF and OH , and the role of oxygen vacancy on Co O are initially unraveled. Correspondingly, instead of the competitive adsorption of OH and HMF on the metal sites, it is observed that the OH can fill into oxygen vacancy (Vo) prior to couple with organic molecules through lattice oxygen oxidation reaction process, which could accelerate the rate-determining step of the dehydrogenation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) intermediates. With the modulated adsorption sites, the as-designed Vo-Co O shows excellent activity for HMFOR with the earlier potential of 90 and 120 mV at 10 mA cm in 1 m KOH and 1 m PBS solution. This work sheds insight on the catalytic mechanism of oxygen vacancy, which benefits designing a novel electrocatalysts to modulate the multi-molecules combined adsorption behaviors.
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http://dx.doi.org/10.1002/adma.202107185DOI Listing
October 2021

Coupling Glucose-Assisted Cu(I)/Cu(II) Redox with Electrochemical Hydrogen Production.

Adv Mater 2021 Dec 24;33(48):e2104791. Epub 2021 Sep 24.

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China.

Water electrolysis is a sustainable technology for hydrogen production since this process can utilize the intermittent electricity generated by renewable energy such as solar, wind, and hydro. However, the large-scale application of this process is restricted by the high electricity consumption due to the large potential gap (>1.23 V) between the anodic oxygen evolution reaction and the cathodic hydrogen evolution reaction (HER). Herein, a novel and efficient hydrogen production system is developed for coupling glucose-assisted Cu(I)/Cu(II) redox with HER. The onset potential of the electrooxidation of Cu(I) to Cu(II) is as low as 0.7 V (vs reversible hydrogen electrode). In situ Raman spectroscopy, ex situ X-ray photoelectron spectroscopy, and density functional theory calculation demonstrates that glucose in the electrolyte can reduce the Cu(II) into Cu(I) instantaneously via a thermocatalysis process, thus completing the cycle of Cu(I)/Cu(II) redox. The assembled electrolyzer only requires a voltage input of 0.92 V to achieve a current density of 100 mA cm . Consequently, the electricity consumption for per cubic H produced in the system is 2.2 kWh, only half of the value for conventional water electrolysis (4.5 kWh). This work provides a promising strategy for the low-cost, efficient production of high-purity H .
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http://dx.doi.org/10.1002/adma.202104791DOI Listing
December 2021

Coupling Electrocatalytic Nitric Oxide Oxidation over Carbon Cloth with Hydrogen Evolution Reaction for Nitrate Synthesis.

Angew Chem Int Ed Engl 2021 Nov 7;60(46):24605-24611. Epub 2021 Oct 7.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, China.

NO is a harmful pollutant to the environment. The traditional removal of NO is hindered by the harsh operating conditions and sacrifice of value-added chemicals. Efficient electrocatalytic oxidation of NO was achieved over plasma-treated commercial carbon cloth, serving as a promising anode substitution reaction to couple with the hydrogen evolution reaction without consumption of hydrogen-containing resources. The introduction of carboxyl groups onto the carbon cloth boosted the electrocatalytic activity via the enhancement of NO chemisorption. Only potentials of 1.39 V and 1.07 V were applied to reach the current density of 10 mA cm in neutral and acidic conditions, respectively, which is superior to the state-of-the-art electrocatalysts for oxygen evolution. Energy and environmental concerns on fossil-fuel-derived hydrogen production, ammonia manufacture and nitrate synthesis, are greatly alleviated. This work provides an original strategy to realize the resource utilization of NO, the sustainable nitrate synthesis and hydrogen production in a green and economical way.
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http://dx.doi.org/10.1002/anie.202109905DOI Listing
November 2021

Platinum Modulates Redox Properties and 5-Hydroxymethylfurfural Adsorption Kinetics of Ni(OH) for Biomass Upgrading.

Angew Chem Int Ed Engl 2021 10 14;60(42):22908-22914. Epub 2021 Sep 14.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.

Nickel hydroxide (Ni(OH) ) is a promising electrocatalyst for the 5-hydroxymethylfurfural oxidation reaction (HMFOR) and the dehydronated intermediates Ni(OH)O species are proved to be active sites for HMFOR. In this study, Ni(OH) is modified by platinum to adjust the electronic structure and the current density of HMFOR improves 8.2 times at the Pt/Ni(OH) electrode compared with that on Ni(OH) electrode. Operando methods reveal that the introduction of Pt optimized the redox property of Ni(OH) and accelerate the formation of Ni(OH)O during the catalytic process. Theoretical studies demonstrate that the enhanced Ni(OH)O formation kinetics originates from the reduced dehydrogenation energy of Ni(OH) . The product analysis and transition state simulation prove that the Pt also reduces adsorption energy of HMF with optimized adsorption behavior as Pt can act as the adsorption site of HMF. Overall, this work here provides a strategy to design an efficient and universal nickel-based catalyst for HMF electro-oxidation, which can also be extended to other Ni-based catalysts such as Ni(HCO ) and NiO.
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http://dx.doi.org/10.1002/anie.202109211DOI Listing
October 2021

Defect-Rich High-Entropy Oxide Nanosheets for Efficient 5-Hydroxymethylfurfural Electrooxidation.

Angew Chem Int Ed Engl 2021 09 29;60(37):20253-20258. Epub 2021 Jul 29.

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.

High-entropy oxides (HEOs), a new concept of entropy stabilization, exhibit unique structures and fascinating properties, and are thus important class of materials with significant technological potential. However, the conventional high-temperature synthesis techniques tend to afford micron-scale HEOs with low surface area, and the catalytic activity of available HEOs is still far from satisfactory because of their limited exposed active sites and poor intrinsic activity. Here we report a low-temperature plasma strategy for preparing defect-rich HEOs nanosheets with high surface area, and for the first time employ them for 5-hydroxymethylfurfural (HMF) electrooxidation. Owing to the nanosheets structure, abundant oxygen vacancies, and high surface area, the quinary (FeCrCoNiCu) O nanosheets deliver improved activity for HMF oxidation with lower onset potential and faster kinetics, outperforming that of HEOs prepared by high-temperature method. Our method opens new opportunities for synthesizing nanostructured HEOs with great potential applications.
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http://dx.doi.org/10.1002/anie.202107390DOI Listing
September 2021

An Investigation of Active Sites for electrochemical CO Reduction Reactions: From In Situ Characterization to Rational Design.

Adv Sci (Weinh) 2021 May 3;8(9):2003579. Epub 2021 Mar 3.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics Provincial Hunan Key Laboratory for Graphene Materials and Devices College of Chemistry and Chemical Engineering the National Supercomputer Centers in Changsha Hunan University Changsha 410082 P. R. China.

The electrochemical carbon dioxide (CO) reduction reaction (CORR) is among the most promising approaches used to transform greenhouse gas into useful fuels and chemicals. However, the reaction suffers from low selectivity, high overpotential, and low reaction rate. Active site identification in the CORR is vital for the understanding of the reaction mechanism and the rational development of new electrocatalysts with both high selectivity and stability. Herein, in situ characterization monitoring of active sites during the reaction is summarized and a general understanding of active sites on the various catalysts in the CORR, including metal-based catalysts, carbon-based catalysts, and metal-organic frameworks-based electrocatalysts is updated. For each type of electrocatalysts, the reaction pathway and real active sites are proposed based on in situ characterization techniques and theoretical calculations. Finally, the key limitations and challenges observed for the electrochemical fixation of CO is presented. It is expected that this review will provide new insights and directions into further scientific development and practical applicability of CO electroreduction.
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http://dx.doi.org/10.1002/advs.202003579DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8097356PMC
May 2021

Li Selectivity of Carboxylate Graphene Nanopores Inspired by Electric Field and Nanoconfinement.

Small 2021 Dec 5;17(48):e2006704. Epub 2021 Mar 5.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.

The regulation of the ion selectivity by electric field and ion association on the Li selectivity of carboxyl functionalized graphene nanopores are investigated by molecular dynamics simulation. Carboxylate graphene nanopores of sub-2 nm exhibit excellent Li selectivity under the electric field of 1.0 V nm . The results show that ion association inspired by electric field may be a key factor affecting ion selectivity of sub-2 nm nanopores. The ion association of Mg and Cl can be promoted obviously near the nanopores under the electric field of 1.0 V nm . The migrating of Mg can be retarded by stable clusters of Mg and Cl formed near nanopores. The degree of association of Li with Cl is relatively low and the disassociation of the Li cluster is easier so that Li can more easily pass through the nanopores. These results gain insight into the effect of ion association inspired by electric field and nanoconfinement of graphene nanopore on Mg /Li separation, and provide helpful information for the application of nanoporous materials in extraction of Li ion from salt-lake brine.
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http://dx.doi.org/10.1002/smll.202006704DOI Listing
December 2021

Tuning the Selective Adsorption Site of Biomass on Co O by Ir Single Atoms for Electrosynthesis.

Adv Mater 2021 Feb 20;33(8):e2007056. Epub 2021 Jan 20.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, National Supercomputer Centers in Changsha, Hunan University, Changsha, 410082, P. R. China.

The electrosynthesis from 5-hydroxymethylfurfural (HMF) is considered a green strategy to achieve biomass-derived high-value chemicals. As the molecular structure of HMF is relatively complicated, understanding the HMF adsorption/catalysis behavior on electrocatalysts is vital for biomass-based electrosynthesis. The electrocatalysis behavior can be modulated by tuning the adsorption energy of the reactive molecules. In this work, the HMF adsorption behavior on spinel oxide, Co O is discovered. Correspondingly, the adsorption energy of HMF on Co O is successfully tuned by decorating with single-atom Ir. It is observed that compared with bare Co O , single-atom-Ir-loaded Co O (Ir-Co O ) can enhance adsorption with the CC groups of HMF. The synergetic adsorption can enhance the overall conversion of HMF on electrocatalysts. With the modulated HMF adsorption, the as-designed Ir-Co O exhibits a record performance (with an onset potential of 1.15 V ) for the electrosynthesis from HMF.
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http://dx.doi.org/10.1002/adma.202007056DOI Listing
February 2021

Defect Chemistry Special Collection.

Chem Asian J 2021 Jan 30;16(2):112-113. Epub 2020 Dec 30.

School of Environment and Science, Griffith University, Nathan, QLD 4111, Australia.

Engineering defects in materials to tune their properties for different applications has gained momentum in recent years. Chemistry - An Asian Journal and ChemNanoMat, together with Prof. Shuangyin Wang (Hunan University, China), Prof. Qiang Zhang (Tsinghua University, China), Prof. Wei Zhang (Shaanxi Normal University, China), and Prof. Yi Jia (Griffith University, Australia) are greatly honored to assemble a special collection of the latest works on Defect Chemistry, directed mainly towards electrocatalysis, photocatalysis, and electrochemical energy storage.
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http://dx.doi.org/10.1002/asia.202001269DOI Listing
January 2021

Unveiling the Electrooxidation of Urea: Intramolecular Coupling of the N-N Bond.

Angew Chem Int Ed Engl 2021 03 22;60(13):7297-7307. Epub 2021 Feb 22.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China.

The nitrogenous nucleophile electrooxidation reaction (NOR) plays a vital role in the degradation and transformation of available nitrogen. Focusing on the NOR mediated by the β-Ni(OH) electrode, we decipher the transformation mechanism of the nitrogenous nucleophile. For the two-step NOR, proton-coupled electron transfer (PCET) is the bridge between electrocatalytic dehydrogenation from β-Ni(OH) to β-Ni(OH)O, and the spontaneous nucleophile dehydrogenative oxidation reaction. This theory can give a good explanation for hydrazine and primary amine oxidation reactions, but is insufficient for the urea oxidation reaction (UOR). Through operando tracing of bond rupture and formation processes during the UOR, as well as theoretical calculations, we propose a possible UOR mechanism whereby intramolecular coupling of the N-N bond, accompanied by PCET, hydration and rearrangement processes, results in high performance and ca. 100 % N selectivity. These discoveries clarify the evolution of nitrogenous molecules during the NOR, and they elucidate fundamental aspects of electrocatalysis involving nitrogen-containing species.
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http://dx.doi.org/10.1002/anie.202015773DOI Listing
March 2021

Electroreduction of Carbon Dioxide Driven by the Intrinsic Defects in the Carbon Plane of a Single Fe-N Site.

Adv Mater 2021 Jan 26;33(1):e2003238. Epub 2020 Nov 26.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.

Manipulating the in-plane defects of metal-nitrogen-carbon catalysts to regulate the electroreduction reaction of CO (CO RR) remains a challenging task. Here, it is demonstrated that the activity of the intrinsic carbon defects can be dramatically improved through coupling with single-atom Fe-N sites. The resulting catalyst delivers a maximum CO Faradaic efficiency of 90% and a CO partial current density of 33 mA cm in 0.1 m KHCO The remarkable enhancements are maintained in concentrated electrolyte, endowing a rechargeable Zn-CO battery with a high CO selectivity of 86.5% at 5 mA cm . Further analysis suggests that the intrinsic defect is the active sites for CO RR, instead of the Fe-N center. Density functional theory calculations reveal that the Fe-N coupled intrinsic defect exhibits a reduced energy barrier for CO RR and suppresses the hydrogen evolution activity. The high intrinsic activity, coupled with fast electron-transfer capability and abundant exposed active sites, induces excellent electrocatalytic performance.
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http://dx.doi.org/10.1002/adma.202003238DOI Listing
January 2021

Non-Metal Single-Phosphorus-Atom Catalysis of Hydrogen Evolution.

Angew Chem Int Ed Engl 2020 Dec 22;59(52):23791-23799. Epub 2020 Oct 22.

The School of Chemistry and Chemical Engineering, State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, 174 Shazheng Street, Shapingba District, Chongqing City, 400044, P. R. China.

Non-metal-based single-atom catalysts (SACs) offer low cost, simple synthesis methods, and effective regulation for substrates. Herein, we developed a simplified pressurized gas-assisted process, and report the first non-metal single-atom phosphorus with atomic-level dispersion on unique single-crystal Mo C hexagonal nanosheet arrays with a (001) plane supported by carbon sheet (SAP-Mo C-CS). The SAP-Mo C-CS is structurally stable and shows exceptional electrocatalytic activity for the hydrogen evolution reaction (HER). A so-called high-active "window" based on the active sites of P atoms and their adjacent Mo atoms gives a ΔG close to zero for hydrogen evolution, which is the most ideal ΔG reported so far. Meanwhile, the moderate d-band center value of SAP-Mo C-CS can be also used as an ideal standard value to evaluate the HER performance in non-metal-based SACs.
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http://dx.doi.org/10.1002/anie.202011358DOI Listing
December 2020

Regulation of Morphology and Electronic Structure of NiSe by Fe for High Effective Oxygen Evolution Reaction.

Chem Asian J 2020 Nov 14;15(22):3845-3852. Epub 2020 Oct 14.

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.

With the development of hydrogen-energy economy, it is urgent for researchers to explore high effective non-noble metal electrocatalysts for oxygen evolution reaction (OER). Nickel-based selenides have good conductivity and easy to regulate, which make them to be a promising OER electrocatalysts. Hence, many researchers engineering the structure of Nickel-based selenides to further improve the OER performance. In this paper, NixFe Se porous-nano-microspheres with different ratio were synthesized. Results confirm that Fe not only affects the number of active sites in NiSe , but also affects the intrinsic activity by forming lattice defects. Besides, introduction of Fe can change the redox ability of Ni cation and Se anion, thus, reducing the average valence state of Ni cation in NiOOH. As a result, the current density of OER is improved remarkably. When the current density reaches 10 mA cm , the overpotential is only 285 mV.
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http://dx.doi.org/10.1002/asia.202000860DOI Listing
November 2020

Sulfur-Rich (NH)MoS as a Highly Reversible Anode for Sodium/Potassium-Ion Batteries.

ACS Nano 2020 Aug 13;14(8):9626-9636. Epub 2020 Aug 13.

Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education, Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics & Devices School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China.

Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have attracted much attention owing to the inexpensive Na/K metal and satisfactory performance. Currently, there are still difficulties in research anode materials that can insert/extract Na/K ions quickly and stably. Herein, the sulfur-rich (NH)MoS is proposed as the anode for SIBs/PIBs and is obtained by a hydrothermal method. The sulfur-rich (NH)MoS with a three-dimensional structure shows a high capacity and long lifespans for Na (at 10 A g the capacity of 165.2 mAh g after 1100 cycles) and K (120.7 mAh g at 1 A g retained after 500 cycles) storage. In addition, the (NH)MoS electrode exhibits excellent electrochemical performance at low temperatures (0 °C). The mechanism of Na storage in (NH)MoS can be innovatively revealed through the combined use of electrochemical kinetic analysis and a series of characterization tests. It is believed that the present work identifies (NH)MoS as a promising anode for the SIBs/PIBs and will be of broad interest in research on engineering sulfur-rich transition metal sulfide and on energy storage devices.
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http://dx.doi.org/10.1021/acsnano.0c00101DOI Listing
August 2020

Identifying the Geometric Site Dependence of Spinel Oxides for the Electrooxidation of 5-Hydroxymethylfurfural.

Angew Chem Int Ed Engl 2020 10 26;59(43):19215-19221. Epub 2020 Aug 26.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, the, National Supercomputer Centers in Changsha, Institution Hunan University, Changsha, 410082, P. R. China.

Co-based spinel oxides, which are of mixing valences with the presence of both Co and Co at different atom locations, are considered as promising catalysts for the electrochemical oxidation of 5-hydroxymethylfurfural (HMF). Identifying the role of each atom site in the electroxidation of HMF is critical to design the advanced electrocatalysts. In this work, we found that Co in Co O is capable of chemical adsorption for acidic organic molecules, and Co play a decisive role in HMF oxidation. Thereafter, the Cu was introduced in spinel oxides to enhance the exposure degree of Co and to boost acidic adsorption and thus to enhance the electrocatalytic activity for HMF electrooxidation significantly.
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http://dx.doi.org/10.1002/anie.202007767DOI Listing
October 2020

Coupling N and CO in HO to synthesize urea under ambient conditions.

Nat Chem 2020 08 15;12(8):717-724. Epub 2020 Jun 15.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, P. R. China.

The use of nitrogen fertilizers has been estimated to have supported 27% of the world's population over the past century. Urea (CO(NH)) is conventionally synthesized through two consecutive industrial processes, N + H → NH followed by NH + CO → urea. Both reactions operate under harsh conditions and consume more than 2% of the world's energy. Urea synthesis consumes approximately 80% of the NH produced globally. Here we directly coupled N and CO in HO to produce urea under ambient conditions. The process was carried out using an electrocatalyst consisting of PdCu alloy nanoparticles on TiO nanosheets. This coupling reaction occurs through the formation of C-N bonds via the thermodynamically spontaneous reaction between *N=N* and CO. Products were identified and quantified using isotope labelling and the mechanism investigated using isotope-labelled operando synchrotron-radiation Fourier transform infrared spectroscopy. A high rate of urea formation of 3.36 mmol g h and corresponding Faradic efficiency of 8.92% were measured at -0.4 V versus reversible hydrogen electrode.
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http://dx.doi.org/10.1038/s41557-020-0481-9DOI Listing
August 2020

Identification of the Dynamic Behavior of Oxygen Vacancy-Rich CoO for Oxygen Evolution Reaction.

J Am Chem Soc 2020 Jul 29;142(28):12087-12095. Epub 2020 Jun 29.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, Hunan 410082, P. R. China.

The exact role of a defect structure on transition metal compounds for electrocatalytic oxygen evolution reaction (OER), which is a very dynamic process, remains unclear. Studying the structure-activity relationship of defective electrocatalysts under conditions is crucial for understanding their intrinsic reaction mechanism and dynamic behavior of defect sites. CoO with rich oxygen vacancy (V) has been reported to efficiently catalyze OER. Herein, we constructed pure spinel CoO and V-rich CoO as catalyst models to study the defect mechanism and investigate the dynamic behavior of defect sites during the electrocatalytic OER process by various characterizations. electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) implied that the V could facilitate the pre-oxidation of the low-valence Co (Co, part of which was induced by the V to balance the charge) at a relatively lower applied potential. This observation confirmed that the V could initialize the surface reconstruction of V-CoO prior to the occurrence of the OER process. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) results further demonstrated the oxygen vacancies were filled with OH first for V-CoO and facilitated pre-oxidation of low-valence Co and promoted reconstruction/deprotonation of intermediate Co-OOH. This work provides insight into the defect mechanism in CoO for OER in a dynamic way by observing the surface dynamic evolution process of defective electrocatalysts and identifying the real active sites during the electrocatalysis process. The current finding would motivate the community to focus more on the dynamic behavior of defect electrocatalysts.
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http://dx.doi.org/10.1021/jacs.0c00257DOI Listing
July 2020

In Situ Exfoliation and Pt Deposition of Antimonene for Formic Acid Oxidation via a Predominant Dehydrogenation Pathway.

Research (Wash D C) 2020 21;2020:5487237. Epub 2020 Feb 21.

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China.

Direct formic acid fuel cell (DFAFC) has been considered as a promising energy conversion device for stationary and mobile applications. Advanced platinum (Pt) electrocatalysts for formic acid oxidation reaction (FAOR) are critical for DFAFC. However, the oxidation of formic acid on Pt catalysts often occurs via a dual pathway mechanism, which hinders the catalytic activity owing to the CO poisoning. Herein, we directly exfoliate bulk antimony to 2D antimonene (Sb) and load Pt nanoparticles onto antimonene sheets with the assistance of ethylenediamine. According to the Bader charge analysis, the charge transfer from antimonene to Pt occurs, confirming the electronic interaction between Pt and Sb. Interestingly, antimonene, as a cocatalyst, alters the oxidation pathway for FAOR over Pt catalyst and makes FAOR follow the more efficient dehydrogenation pathway. The density functional theory (DFT) calculation demonstrates that antimonene can activate Pt to be a lower oxidative state and facilitate the oxidation of HCOOH into CO via a direct pathway, resulting in a weakened intermediate binding strength and better CO tolerance for FAOR. The specific activity of FAOR on Pt/Sb is 4.5 times, and the mass activity is 2.6 times higher than the conventional Pt/C.
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http://dx.doi.org/10.34133/2020/5487237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054718PMC
February 2020

Defect Engineering for Fuel-Cell Electrocatalysts.

Adv Mater 2020 May 16;32(19):e1907879. Epub 2020 Mar 16.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, The National Supercomputing Center in Changsha, Hunan University, Changsha, 410082, P. R. China.

The commercialization of fuel cells, such as proton exchange membrane fuel cells and direct methanol/formic acid fuel cells, is hampered by their poor stability, high cost, fuel crossover, and the sluggish kinetics of platinum (Pt) and Pt-based electrocatalysts for both the cathodic oxygen reduction reaction (ORR) and the anodic hydrogen oxidation reaction (HOR) or small molecule oxidation reaction (SMOR). Thus far, the exploitation of active and stable electrocatalysts has been the most promising strategy to improve the performance of fuel cells. Accordingly, increasing attention is being devoted to modulating the surface/interface electronic structure of electrocatalysts and optimizing the adsorption energy of intermediate species by defect engineering to enhance their catalytic performance. Defect engineering is introduced in terms of defect definition, classification, characterization, construction, and understanding. Subsequently, the latest advances in defective electrocatalysts for ORR and HOR/SMOR in fuel cells are scientifically and systematically summarized. Furthermore, the structure-activity relationships between defect engineering and electrocatalytic ability are further illustrated by coupling experimental results and theoretical calculations. With a deeper understanding of these complex relationships, the integration of defective electrocatalysts into single fuel-cell systems is also discussed. Finally, the potential challenges and prospects of defective electrocatalysts are further proposed, covering controllable preparation, in situ characterization, and commercial applications.
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http://dx.doi.org/10.1002/adma.201907879DOI Listing
May 2020

Identifying the Intrinsic Relationship between the Restructured Oxide Layer and Oxygen Evolution Reaction Performance on the Cobalt Pnictide Catalyst.

Small 2020 Apr 12;16(14):e1906867. Epub 2020 Mar 12.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, Hunan, China.

Cobalt pnictides show good catalytic activity and stability on oxygen evolution reaction (OER) behaviors in a strong alkaline solution. Identifying the intrinsic composition/structure-property relationship of the oxide layer on the cobalt pnictides is critical to design better and cheaper electrocatalysts for the commercial viability of OER technologies. In this work, the restructured oxide layer on the cobalt pnictides and its effect on the activity and mechanism for OER is systematically analyzed. In-situ electrochemical impedance spectroscopy (EIS) and near edge x-ray absorption fine structure (NEXAFS) spectra indicate that a higher OER performance of cobalt pnictides than Co O is attributed to the more structural disorder and oxygen defect sites in the cobalt oxide layer evolved from cobalt pnictides. Using angle resolved x-ray photoelectron spectroscopy (AR-XPS) further demonstrates that the oxygen defect sites mainly concentrate on the subsurface of cobalt oxide layer. The current study demonstrated promising opportunities for further enhancing the OER performance of cobalt-based electrocatalysts by controlling the subsurface defects of the restructured active layer.
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http://dx.doi.org/10.1002/smll.201906867DOI Listing
April 2020

Bifunctional Catalysts for Reversible Oxygen Evolution Reaction and Oxygen Reduction Reaction.

Chemistry 2020 Feb 14. Epub 2020 Feb 14.

Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.

Metal-air batteries (MABs) and reversible fuel cells (RFCs) rely on the bifunctional oxygen catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Finding efficient bifunctional oxygen catalysts is the ultimate goal and it has attracted a great deal of attention. The dilemma is that a good ORR catalyst is not necessarily efficient for OER, and vice versa. Thus, the development of a new type of bifunctional oxygen catalysts should ensure that the catalysts exhibit high activity for both OER and ORR. Composites with multicomponents for active centers supported on highly conductive matrices could be able to meet the challenges and offering new opportunities. In this Review, the evolution of bifunctional catalysts is summarized and discussed aiming to deliver high-performance bifunctional catalysts with low overpotentials.
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http://dx.doi.org/10.1002/chem.201905346DOI Listing
February 2020

Three-Dimensional Self-assembled Hairball-Like VS as High-Capacity Anodes for Sodium-Ion Batteries.

Nanomicro Lett 2020 Jan 25;12(1):39. Epub 2020 Jan 25.

Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education, Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China.

Sodium-ion batteries (SIBs) are considered to be attractive candidates for large-scale energy storage systems because of their rich earth abundance and consistent performance. However, there are still challenges in developing desirable anode materials that can accommodate rapid and stable insertion/extraction of Na and can exhibit excellent electrochemical performance. Herein, the self-assembled hairball-like VS as anodes of SIBs exhibits high discharge capacity (660 and 589 mAh g at 1 and 3 A g, respectively) and excellent rate property (about 100% retention at 10 and 20 A g after 1000 cycles) at room temperature. Moreover, the VS can also exhibit 591 mAh g at 1 A g after 600 cycles at 0 °C. An unlike traditional mechanism of VS for Na storage was proposed according to the dates of ex situ characterization, cyclic voltammetry, and electrochemical kinetic analysis. The capacities of the final stabilization stage are provided by the reactions of reversible transformation between NaS and S, which were considered the reaction mechanisms of Na-S batteries. This work can provide a basis for the synthesis and application of sulfur-rich compounds in fields of batteries, semiconductor devices, and catalysts.
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http://dx.doi.org/10.1007/s40820-020-0377-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7770669PMC
January 2020

Defect Engineering on Electrode Materials for Rechargeable Batteries.

Adv Mater 2020 Feb 13;32(7):e1905923. Epub 2020 Jan 13.

State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, the National Supercomputer Centers in Changsha, Hunan University, Changsha, 410082, P. R. China.

The reasonable design of electrode materials for rechargeable batteries plays an important role in promoting the development of renewable energy technology. With the in-depth understanding of the mechanisms underlying electrode reactions and the rapid development of advanced technology, the performance of batteries has significantly been optimized through the introduction of defect engineering on electrode materials. A large number of coordination unsaturated sites can be exposed by defect construction in electrode materials, which play a crucial role in electrochemical reactions. Herein, recent advances regarding defect engineering in electrode materials for rechargeable batteries are systematically summarized, with a special focus on the application of metal-ion batteries, lithium-sulfur batteries, and metal-air batteries. The defects can not only effectively promote ion diffusion and charge transfer but also provide more storage/adsorption/active sites for guest ions and intermediate species, thus improving the performance of batteries. Moreover, the existing challenges and future development prospects are forecast, and the electrode materials are further optimized through defect engineering to promote the development of the battery industry.
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http://dx.doi.org/10.1002/adma.201905923DOI Listing
February 2020

Regulating Hydrogenation Chemoselectivity of α,β-Unsaturated Aldehydes by Combination of Transfer and Catalytic Hydrogenation.

ChemSusChem 2020 Apr 18;13(7):1746-1750. Epub 2020 Feb 18.

State Key Laboratory of Chem/Bio-sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P.R. China.

Two hydrogenation mechanisms, transfer and catalytic hydrogenation, were combined to achieve higher regulation of hydrogenation chemoselectivity of cinnamyl aldehydes. Transfer hydrogenation with ammonia borane exclusively reduced C=O bonds to get cinnamyl alcohol, and Pt-loaded metal-organic layers efficiently hydrogenated C=C bonds to synthesize phenyl propanol with almost 100 % conversion rate. The hydrogenation could be performed under mild conditions without external high-pressure hydrogen and was applicable to various α,β-unsaturated aldehydes.
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http://dx.doi.org/10.1002/cssc.201902629DOI Listing
April 2020

Optimal Geometrical Configuration of Cobalt Cations in Spinel Oxides to Promote Oxygen Evolution Reaction.

Angew Chem Int Ed Engl 2020 Mar 31;59(12):4736-4742. Epub 2020 Jan 31.

State Key Laboratory of Chem/Bio-sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.

MgCo O , CoCr O , and Co TiO were selected, where only Co in the center of octahedron (Oh), Co in the center of tetrahedron (Td), and Co in the center of Oh, can be active sites for the oxygen evolution reaction (OER). Co (Oh) sites are the best geometrical configuration for OER. Co (Oh) sites exhibit better activity than Co (Td). Calculations demonstrate the conversion of O* into OOH* is the rate-determining step for Co (Oh) and Co (Td). For Co (Oh), it is thermodynamically favorable for the formation of OOH* but difficult for the desorption of O . Co (Oh) needs to increase the lowest Gibbs free energy over Co (Oh) and Co (Td), which contributes to the best activity. The coexistence of Co (Oh) and Co (Td) in Co O can promote the formation of OOH* and decrease the free-energy barrier. This work screens out the optimal geometrical configuration of cobalt cations for OER and gives a valuable principle to design efficient electrocatalysts.
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http://dx.doi.org/10.1002/anie.201914245DOI Listing
March 2020

Hierarchically Ordered Porous Carbon with Atomically Dispersed FeN for Ultraefficient Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells.

Angew Chem Int Ed Engl 2020 Feb 28;59(7):2688-2694. Epub 2020 Jan 28.

State Key Laboratory of Chem/Bio-Sensing and Chemometrics,Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.

The low catalytic activity and poor mass transport capacity of platinum group metal free (PGM-free) catalysts seriously restrict the application of proton-exchange membrane fuel cells (PEMFCs). Catalysts derived from Fe-doped ZIF-8 could in theory be as active as Pt/C thanks to the high intrinsic activity of FeN ; however, the micropores fail to meet rapid mass transfer. Herein, an ordered hierarchical porous structure is introduced into Fe-doped ZIF-8 single crystals, which were subsequently carbonized to obtain an FeN -doped hierarchical ordered porous carbon (FeN /HOPC) skeleton. The optimal catalyst FeN /HOPC-c-1000 shows excellent performance with a half-wave potential of 0.80 V in 0.5 m H SO solution, only 20 mV lower than that of commercial Pt/C (0.82 V). In a real PEMFC, FeN /HOPC-c-1000 exhibits significantly enhanced current density and power density relative to FeN /C, which does not have an optimized pore structure, implying an efficient utilization of the active sites and enhanced mass transfer to promote the oxygen reduction reaction (ORR).
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http://dx.doi.org/10.1002/anie.201914123DOI Listing
February 2020

Defects-Induced In-Plane Heterophase in Cobalt Oxide Nanosheets for Oxygen Evolution Reaction.

Small 2019 Dec 14;15(50):e1904903. Epub 2019 Nov 14.

State Key Laboratory of Chem/Bio-sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China.

Cobalt oxides as efficient oxygen evolution reaction (OER) electrocatalysts have received much attention because of their rich reserves and cheap cost. There are two common cobalt oxides, Co O (spinel phase, stable but poor intrinsic activity) and CoO (rocksalt phase, active but easily be oxidatized). Constructing Co O /CoO heterophase can inherit both characteristic features of each component and form a heterophase interface facilitating charge transfer, which is believed to be an effective strategy in designing excellent electrocatalysts. Herein, an atomic arrangement engineering strategy is applied to improve electrocatalytic activity of Co O for the OER. With the presence of oxygen vacancies, cobalt atoms at tetrahedral sites in Co O can more easily diffuse into interstitial octahedral sites to form CoO phase structure as revealed by periodic density functional theory computations. The Co O /CoO spinel/rocksalt heterophase can be in situ fabricated at the atomic scale in plane. The overpotential to reach 10 mA cm of Co O /CoO is 1.532 V, which is 92 mV smaller than that of Co O . Theoretical calculations confirm that the excellent electrochemical activity is corresponding to a decline in average p-state energy of adsorbed-O on the Co O /CoO heterophase interface. The reaction Gibbs energy barrier has been significantly decreased with the construction of the heterophase interface.
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http://dx.doi.org/10.1002/smll.201904903DOI Listing
December 2019

Quinary Defect-Rich Ultrathin Bimetal Hydroxide Nanosheets for Water Oxidation.

ACS Appl Mater Interfaces 2019 Nov 14;11(47):44018-44025. Epub 2019 Nov 14.

State Key Laboratory of Chem/Bio-sensing and Chemometrics, College of Chemistry and Chemical Engineering , Hunan University , Changsha 410082 , China.

The electronic structure of layered double hydroxides (LDHs) can be modulated by heteroatom doping and creating vacancies. The number of exposed active sites can be enriched by exfoliating the bulk structure into fewer layers. Herein, we successfully achieved multielement doping and exfoliation for CoFe LDHs by one SF-plasma etching step at room temperature (named as CoFe LDHs-SF). The obtained CoFe LDHs-SF ultrathin nanosheets display outstanding oxygen evolution reaction (OER) activity, which only needs 268 mV overpotential to reach 10 mA cm. Tafel slope and charge transfer resistance are dramatically decreased indicating a faster reaction kinetic rate. The excellent OER activity can be attributed to an increased number of active sites and an optimized electronic structure modulated by the incorporation of electron-withdrawing F, electron-donating S, and abundant vacancies resulting in proper adsorption energy to oxygen species.
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http://dx.doi.org/10.1021/acsami.9b10315DOI Listing
November 2019
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