Publications by authors named "Daping He"

29 Publications

  • Page 1 of 1

Ternary Alloys Enable Efficient Production of Methoxylated Chemicals via Selective Electrocatalytic Hydrogenation of Lignin Monomers.

J Am Chem Soc 2021 10 7;143(41):17226-17235. Epub 2021 Oct 7.

Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong 518060, China.

We explore the selective electrocatalytic hydrogenation of lignin monomers to methoxylated chemicals, of particular interest, when powered by renewable electricity. Prior studies, while advancing the field rapidly, have so far lacked the needed selectivity: when hydrogenating lignin-derived methoxylated monomers to methoxylated cyclohexanes, the desired methoxy group (-OCH) has also been reduced. The ternary PtRhAu electrocatalysts developed herein selectively hydrogenate lignin monomers to methoxylated cyclohexanes-molecules with uses in pharmaceutics. Using X-ray absorption spectroscopy and Raman spectroscopy, we find that Rh and Au modulate the electronic structure of Pt and that this modulating steers intermediate energetics on the electrocatalyst surface to facilitate the hydrogenation of lignin monomers and suppress C-OCH bond cleavage. As a result, PtRhAu electrocatalysts achieve a record 58% faradaic efficiency (FE) toward 2-methoxycyclohexanol from the lignin monomer guaiacol at 200 mA cm, representing a 1.9× advance in FE and a 4× increase in partial current density compared to the highest productivity prior reports. We demonstrate an integrated lignin biorefinery where wood-derived lignin monomers are selectively hydrogenated and funneled to methoxylated 2-methoxy-4-propylcyclohexanol using PtRhAu electrocatalysts. This work offers an opportunity for the sustainable electrocatalytic synthesis of methoxylated pharmaceuticals from renewable biomass.
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http://dx.doi.org/10.1021/jacs.1c08348DOI Listing
October 2021

A Dual-Band Conformal Antenna Based on Highly Conductive Graphene-Assembled Films for 5G WLAN Applications.

Materials (Basel) 2021 Sep 6;14(17). Epub 2021 Sep 6.

Hubei Engineering Research Center of RF-Microwave Technology and Application, Wuhan University of Technology, Wuhan 430070, China.

Flexible electronic devices are widely used in the Internet of Things, smart home and wearable devices, especially in carriers with irregular curved surfaces. Light weight, flexible and corrosion-resistant carbon-based materials have been extensively investigated in RF electronics. However, the insufficient electrical conductivity limits their further application. In this work, a flexible and low-profile dual-band Vivaldi antenna based on highly conductive graphene-assembled films (GAF) is proposed for 5G Wi-Fi applications. The proposed GAF antenna with the profile of 0.548 mm comprises a split ring resonator and open circuit half wavelength resonator to implement the dual band-notched characteristic. The operating frequency of the flexible GAF antenna covers the Wi-Fi 6e band, 2.4-2.45 GHz and 5.15-7.1 GHz. Different conformal applications are simulated by attaching the antenna to the surface of cylinders with different radii. The measured results show that the working frequency bands and the radiation patterns of the GAF antenna are relatively stable, with a bending angle of 180°. For demonstration of practical application, the GAF antennas are conformed to a commercial router. The spectral power of the GAF antenna router is greater than the copper antenna router, which means a higher signal-to-noise ratio and a longer transmission range can be achieved. All results indicate that the proposed GAF antenna has broad application prospects in next generation Wi-Fi.
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http://dx.doi.org/10.3390/ma14175087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8434397PMC
September 2021

Sulfate Ions Induced Concave Porous S-N Co-Doped Carbon Confined FeC Nanoclusters with Fe-N Sites for Efficient Oxygen Reduction in Alkaline and Acid Media.

Small 2021 Jul 18;17(29):e2101001. Epub 2021 Jun 18.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, China.

To improve the catalytic activity of the catalysts, it is key to intensifying the intrinsic activity of active sites or increasing the exposure of accessible active sites. In this work, an efficient oxygen reduction electrocatalyst is designed that confines plentiful FeC nanoclusters with Fe-N sites in a concave porous S-N co-doped carbon matrix, readily accessible for the oxygen reduction reaction (ORR). Sulfate ions react with the carbon derived from ZIF-8 at high temperatures, leading to the shrinkage of the carbon framework and then forming a concave structure with abundant macropores and mesopores with S incorporation. Such an architecture promotes the exposure of active sites and accelerates remote mass transfer. As a result, the catalyst (Fe/S-NC) with a large number of C-S-C, Fe-N , and FeC nanoclusters presents impressive ORR activity and stability. In alkaline media, the half-wave potential of the best catalyst (Fe/S -NC) is 0.91 V, which far exceeds that of commercial platinum carbon (0.85 V), while in acidic media the half-wave potential reaches 0.784 V, comparable to platinum carbon (0.812 V). Furthermore, for the zinc-air battery, the outstanding peak power density of Fe/S -NC (170 mW cm ) superior to platinum carbon (108 mW cm ) also highlights its great application potential.
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http://dx.doi.org/10.1002/smll.202101001DOI Listing
July 2021

Design Engineering, Synthesis Protocols, and Energy Applications of MOF-Derived Electrocatalysts.

Nanomicro Lett 2021 Jun 1;13(1):132. Epub 2021 Jun 1.

Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory, Xianhu Hydrogen Valley, Foshan, 528200, People's Republic of China.

The core reactions for fuel cells, rechargeable metal-air batteries, and hydrogen fuel production are the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), which are heavily dependent on the efficiency of electrocatalysts. Enormous attempts have previously been devoted in non-noble electrocatalysts born out of metal-organic frameworks (MOFs) for ORR, OER, and HER applications, due to the following advantageous reasons: (i) The significant porosity eases the electrolyte diffusion; (ii) the supreme catalyst-electrolyte contact area enhances the diffusion efficiency; and (iii) the electronic conductivity can be extensively increased owing to the unique construction block subunits for MOFs-derived electrocatalysis. Herein, the recent progress of MOFs-derived electrocatalysts including synthesis protocols, design engineering, DFT calculations roles, and energy applications is discussed and reviewed. It can be concluded that the elevated ORR, OER, and HER performances are attributed to an advantageously well-designed high-porosity structure, significant surface area, and plentiful active centers. Furthermore, the perspectives of MOF-derived electrocatalysts for the ORR, OER, and HER are presented.
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http://dx.doi.org/10.1007/s40820-021-00656-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8169752PMC
June 2021

Hybrid metamaterial absorber for ultra-low and dual-broadband absorption.

Opt Express 2021 Apr;29(9):14078-14086

Developing high-efficiency microwave absorbers remains challenging in the broadband range, particularly in the low-frequency range containing the L band and even lower. To overcome this challenge, a hybrid metamaterial absorber comprising a conventional magnetic absorbing material and a multi-layered meta-structure predesigned with graphene films is proposed to realize wideband absorption performance starting from ultra-low frequencies (0.79-20.9 GHz and 25.1-40.0 GHz). The high absorption ability of the proposed device originates from fundamental resonance modes and their coupling. The experimental results agree well with the simulated ones, proving the effectiveness of our design method. In addition, owing to the use of low-density polymethylacrylimide foam and graphene films with outstanding mechanical properties, our design is lightweight and environmentally adaptable, which reflects its engineering value.
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http://dx.doi.org/10.1364/OE.423245DOI Listing
April 2021

A Graphene-Based Stopband FSS with Suppressed Mutual Coupling in Dielectric Resonator Antennas.

Materials (Basel) 2021 Mar 18;14(6). Epub 2021 Mar 18.

Hubei Engineering Research Center of RF-Microwave Technology and Application, Wuhan University of Technology, Wuhan 430070, China.

A novel stopband frequency-selective surface (FSS) made of high-conductivity graphene assemble films (HCGFs) for reducing the mutual coupling between dielectric resonator antennas (DRAs) is investigated and presented. The FSS is a "Hamburg" structure consisting of a two-layer HCGF and a one-layer dielectric substrate. A laser-engraving technology is applied to fabricate the FSS. The proposed improved Jerusalem cross FSS, compared with cross FSS and Jerusalem cross FSS, can effectively reduce the size of the unit cell by 88.89%. Moreover, the FSS, composing of 2 × 10-unit cells along the E-plane, is proposed and embedded between two DRAs, which nearly has no effect on the reflection coefficient of the antenna. However, the mutual coupling is reduced by more than 7 dB on average (7.16 dB at 3.4 GHz, 7.42 dB at 3.5 GHz, 7.71 dB at 3.6 GHz) with the FSS. The patterns of the antenna are also measured. Therefore, it is suggested that the proposed FSS is a good candidate to reduce mutual coupling in the multiple-input-multiple-output (MIMO) antenna system for 5G communication.
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http://dx.doi.org/10.3390/ma14061490DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8002884PMC
March 2021

Flexible Anti-Metal RFID Tag Antenna Based on High-Conductivity Graphene Assembly Film.

Sensors (Basel) 2021 Feb 22;21(4). Epub 2021 Feb 22.

Hubei Engineering Research Center of RF-Microwave Technology and Application, Wuhan University of Technology, Wuhan 430070, China.

We propose a flexible anti-metal radio frequency identification (RFID) tag antenna based on a high-conductivity graphene assembly film (HCGAF). The HCGAF has a conductivity of 1.82 × 10 S m, a sheet resistance of 25 mΩ and a thickness of 22 μm. The HCGAF is endowed with high conductivity comparable to metal materials and superb flexibility, which is suitable for making antennas for microwave frequencies. Through proper structural design, parameter optimization, semiautomatic manufacturing and experimental measurements, an HCGAF antenna could realize a realized gain of -7.3 dBi and a radiation efficiency of 80%, and the tag could achieve a 6.4 m read range at 915 MHz on a 20 × 20 cm flat copper plate. In the meantime, by utilizing flexible polyethylene (PE) foam, good conformality was obtained. The read ranges of the tags attached to curved copper plates with different bending radii were measured, as well as those of those attached to several daily objects. All the results demonstrate the excellent performance of the design, which is highly favorable for practical RFID anti-metal applications.
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http://dx.doi.org/10.3390/s21041513DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7926944PMC
February 2021

Negative Pressure Pyrolysis Induced Highly Accessible Single Sites Dispersed on 3D Graphene Frameworks for Enhanced Oxygen Reduction.

Angew Chem Int Ed Engl 2020 Nov 4;59(46):20465-20469. Epub 2020 Sep 4.

School of Chemistry and Materials Science, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, 230026, China.

Herein, we report a negative pressure pyrolysis to access dense single metal sites (Co, Fe, Ni etc.) with high accessibility dispersed on three-dimensional (3D) graphene frameworks (GFs), during which the differential pressure between inside and outside of metal-organic frameworks (MOFs) promotes the cleavage of the derived carbon layers and gradual expansion of mesopores. In situ transmission electron microscopy and Brunauer-Emmett-Teller tests reveal that the formed 3D GFs possess an enhanced mesoporosity and external surface area, which greatly favor the mass transport and utilization of metal sites. This contributes to an excellent oxygen reduction reaction (ORR) activity (half-wave potential of 0.901 V vs. RHE). Theoretical calculations verify that selective carbon cleavage near Co centers can efficiently lower the overall ORR theoretical overpotential in comparison with intact atomic configuration.
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http://dx.doi.org/10.1002/anie.202009700DOI Listing
November 2020

Flexible Graphene-Assembled Film-Based Antenna for Wireless Wearable Sensor with Miniaturized Size and High Sensitivity.

ACS Omega 2020 Jun 30;5(22):12937-12943. Epub 2020 May 30.

Hubei Engineering Research Center of RF-Microwave Technology and Application, School of Science, Wuhan University of Technology, Wuhan 430070, P. R. China.

The flexible radio frequency (RF) wireless antennas used as sensors, which can detect signal variation resulting from the deformation of the antenna, have attracted increasing attention with the development of wearable electronic devices and the Internet of Things (IoT). However, miniaturization and sensitivity issues restrict the development of flexible RF sensors. In this work, we demonstrate the application of a flexible and highly conductive graphene-assembled film (GAF) for antenna design. The GAF with a high conductivity of 10 S/m has the advantages of light weight, high flexibility, and superb mechanical stability. As a result, a small-size (50 mm × 50 mm) and flexible GAF-based antenna operating at 3.13-4.42 GHz is achieved, and this GAF antenna-based wireless wearable sensor shows high strain sensitivities of 34.9 for tensile bending and 35.6 for compressive bending. Furthermore, this sensor exhibits good mechanical flexibility and structural stability after a 100-cycle bending test when attached to the back of the hand and the wrist, which demonstrates broad application prospects in health-monitoring devices, electronic skins, and smart robotics.
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http://dx.doi.org/10.1021/acsomega.0c00263DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7288573PMC
June 2020

Compact and Low-Profile UWB Antenna Based on Graphene-Assembled Films for Wearable Applications.

Sensors (Basel) 2020 Apr 30;20(9). Epub 2020 Apr 30.

Hubei Engineering Research Center of RF-Microwave Technology and Application, Wuhan University of Technology, Wuhan 430070, China.

In this article, a graphene-assembled film (GAF)-based compact and low-profile ultra-wide bandwidth (UWB) antenna is presented and tested for wearable applications. The highly conductive GAFs (~10 S/m) together with the flexible ceramic substrate ensure the flexibility and robustness of the antenna, which are two main challenges in designing wearable antennas. Two H-shaped slots are introduced on a coplanar-waveguide (CPW) feeding structure to adjust the current distribution and thus improve the antenna bandwidth. The compact GAF antenna with dimensions of 32 × 52 × 0.28 mm provides an impedance bandwidth of 60% (4.3-8.0 GHz) in simulation. The UWB characteristics are further confirmed by on-body measurements and show a bending insensitive bandwidth of ~67% (4.1-8.0 GHz), with the maximum gain at 7.45 GHz being 3.9 dBi and 4.1 dBi in its flat state and bent state, respectively. Our results suggest that the proposed antenna functions properly in close proximity to a human body and can sustain repetitive bending, which make it well suited for applications in wearable devices.
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http://dx.doi.org/10.3390/s20092552DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7249118PMC
April 2020

Enhanced Silver Nanowire Composite Window Electrode Protected by Large Size Graphene Oxide Sheets for Perovskite Solar Cells.

Nanomaterials (Basel) 2019 Feb 2;9(2). Epub 2019 Feb 2.

School of Science, Wuhan University of Technology, Wuhan 430070, China.

Despite the outstanding features of high transmittance and low sheet resistance from silver nanowire (Ag NW) based transparent electrodes, their applications in perovskite solar cells (PVSCs) as window electrodes encounter significant obstacles due to the stability issue brought by the corrosion of halogen species from perovskite layer. In this study, we used large size graphene oxide (LGO) sheets as the protective barrier for bottom Ag NW nano-network. Contributed by the LGO with average size of 60 μm, less GO sheet was necessary for forming the fully covered protective barrier with fewer cracks, which consequently improved the optical transparency and anticorrosive ability of the composite electrode compared to the one from relatively small size GO. Our experiments demonstrated the composite electrode of Ag NW/LGO. The glass substrate exhibited transmittance of 83.8% and 81.8% at 550 nm before and after partial reduction, which maintained 98.4% and 95.1% average transmittance (AVT) of the pristine Ag NW electrode. Meanwhile, we utilized the steady hot airflow to assist the fast solvent evaporation and the uniform GO film formation on Ag NW electrode. Before the application of composite electrode in organic-inorganic hybrid perovskite solar cells, the operational stability of composite electrodes from different sizes of GO with perovskite film fabricated on top were characterized under continuing external bias and light irradiation. Experimental results indicate that the Ag NW electrode protected by LGO could maintain original resistance for more than 45 h. Finally, the PVSC fabricated on Ag NW/LGO based composite electrode yielded a power conversion efficiency (PCE) of 9.62%, i.e., nearly 85% of that of the reference device fabricated on the commercial indium-tin oxide (ITO) glass. Our proposed low temperature and solution processed bottom electrode with improved optical transparency and operational stability can serve as the very beginning layer of optoelectronic devices, to promote the development of low cost and large area fabrication perovskite solar cells.
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http://dx.doi.org/10.3390/nano9020193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6410413PMC
February 2019

Stabilizing Pt Nanocrystals Encapsulated in N-Doped Carbon as Double-Active Sites for Catalyzing Oxygen Reduction Reaction.

Langmuir 2019 Feb 7;35(7):2580-2586. Epub 2019 Feb 7.

Polypropylene fiber, a cheap source of nitrogen-doped carbon, is introduced to design robust nitrogen-doped carbon-encapsulated small Pt nanocrystals with Pt and nitrogen-carbon double-active centers toward oxygen reduction reaction (ORR). Ascribed to the separation effect of the polypropylene fiber, even suffering from a high-temperature carbonization treatment at 720 °C for 90 min, the polypropylene fiber-derived carbon-encapsulated Pt nanocrystal maintains a small particle size (3 nm diameter on average). As expected, its ORR mass activity is up to 116.5 mA/mg at 0.9 V. After 8000 cycles, the half-wave potential of the prepared catalyst declines only by 14 mV compared with 43 mV for the commercial Pt/C catalyst. The significantly improved electrochemical properties of the as-prepared catalyst are resulted from the nitrogen-doped carbon-encapsulated Pt nanocrystal structure, which is benefited to adsorption and activation of oxygen due to the presence of nitrogen-doped carbon as the important active site for ORR besides Pt metal. In addition, the migration, aggregation, and growth of Pt nanoparticles are prohibited in terms of the outer nitrogen-doped carbon protection layer, greatly enhancing the stability of the catalyst.
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http://dx.doi.org/10.1021/acs.langmuir.8b03947DOI Listing
February 2019

Platinum Nanoparticle Inclusion into a Carbonized Polymer of Intrinsic Microporosity: Electrochemical Characteristics of a Catalyst for Electroless Hydrogen Peroxide Production.

Nanomaterials (Basel) 2018 Jul 18;8(7). Epub 2018 Jul 18.

Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK.

The one-step vacuum carbonization synthesis of a platinum nano-catalyst embedded in a microporous heterocarbon ([email protected]) is demonstrated. A nitrogen-rich polymer of an intrinsic microporosity (PIM) precursor is impregnated with PtCl₆ to give (after vacuum carbonization at 700 °C) a nitrogen-containing heterocarbon with embedded Pt nanoparticles of typically 1⁻4 nm diameter (with some particles up to 20 nm diameter). The Brunauer-Emmett-Teller (BET) surface area of this hybrid material is 518 m² g (with a cumulative pore volume of 1.1 cm³ g) consistent with the surface area of the corresponding platinum-free heterocarbon. In electrochemical experiments, the heterocarbon-embedded nano-platinum is observed as reactive towards hydrogen oxidation, but essentially non-reactive towards bigger molecules during methanol oxidation or during oxygen reduction. Therefore, oxygen reduction under electrochemical conditions is suggested to occur mainly via a 2-electron pathway on the outer carbon shell to give H₂O₂. Kinetic selectivity is confirmed in exploratory catalysis experiments in the presence of H₂ gas (which is oxidized on Pt) and O₂ gas (which is reduced on the heterocarbon surface) to result in the direct formation of H₂O₂.
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http://dx.doi.org/10.3390/nano8070542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6071093PMC
July 2018

Activating rhodium phosphide-based catalysts for the pH-universal hydrogen evolution reaction.

Nanoscale 2018 Jul;10(26):12407-12412

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, P. R. China.

Highly active and stable Pt-free electrocatalysts for hydrogen production via water splitting are of great demand for future energy systems. Herein, we report a novel hydrogen evolution reaction (HER) catalyst consisting of rhodium phosphide (Rh2P) nanoparticles as the core and N-doped carbon (NC) as the shell ([email protected]). In a wide pH range, our catalyst not only possesses a small overpotential at 10 mA cm-2 (∼9 mV in 0.5 M H2SO4, ∼46 mV in 1.0 M PBS and ∼10 mV in 1.0 M KOH), but also demonstrates high stability. Importantly, all these performances are far superior to commercial Pt/C catalysts for HER. To the best of our knowledge, this is the highest HER performance reported so far in acidic and basic media. Density functional theory (DFT) calculations reveal that the introduction of phosphorus can significantly lower the proton adsorption energy of Rh/NC, thereby benefiting surface hydrogen generation. Moreover, this synthetic strategy for [email protected] is also applied to other transition metal phosphides (TMPs)/nitrogen-doped carbon heterostructures (such as [email protected], [email protected], [email protected] etc.) with advanced performance toward HER and beyond.
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http://dx.doi.org/10.1039/c8nr02854kDOI Listing
July 2018

Ultrahigh Conductive Copper/Large Flake Size Graphene Heterostructure Thin-Film with Remarkable Electromagnetic Interference Shielding Effectiveness.

Small 2018 May 17;14(20):e1704332. Epub 2018 Apr 17.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, China.

To guarantee the normal operation of next generation portable electronics and wearable devices, together with avoiding electromagnetic wave pollution, it is urgent to find a material possessing flexibility, ultrahigh conductive, and superb electromagnetic interference shielding effectiveness (EMI SE) simultaneously. In this work, inspired by a building bricks toy with the interlock system, we design and fabricate a copper/large flake size graphene (Cu/LG) composite thin film (≈8.8 μm) in the light of high temperature annealing of a large flake size graphene oxide film followed by magnetron sputtering of copper. The obtained Cu/LG thin-film shows ultrahigh thermal conductivity of over 1932.73 (±63.07) W m K and excellent electrical conductivity of 5.88 (±0.29) × 10 S m . Significantly, it also exhibits a remarkably high EMI SE of over 52 dB at the frequency of 1-18 GHz. The largest EMI SE value of 63.29 dB, accorded at 1 GHz, is enough to obstruct and absorb 99.99995% of incident radiation. To the best of knowledge, this is the highest EMI SE performance reported so far in such thin thickness of graphene-based materials. These outstanding properties make Cu/LG film a promising alternative building block for power electronics, microprocessors, and flexible electronics.
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http://dx.doi.org/10.1002/smll.201704332DOI Listing
May 2018

Mesoporous-silica induced doped carbon nanotube growth from metal-organic frameworks.

Nanoscale 2018 Mar;10(13):6147-6154

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.

Carbon materials, with a controllable structure, derived from metal-organic frameworks (MOFs) have emerged as a new class of electrocatalysts in renewable energy devices. However, efficient conversion of MOFs to small diameter doped carbon nanotubes in inert gases at high temperatures (>600 °C) remains a significant challenge. In this study, we first report the growth of small diameter cobalt and nitrogen co-doped carbon nanotubes (Co/N-CNTs) from mesoporous silica (mSiO2)-coated Co-based MOFs (ZIF-67). The presence of a layer of mSiO2 outside the ZIF-67 nanocrystals prevents the Co nanocatalysts from quick aggregation, and significantly serves as a unique 'sieve' for inducing the catalytic growth of CNTs during pyrolysis. The obtained Co/N-CNTs, with ∼13 nm diameter evolved from the pristine MOF architecture, exhibit higher catalytic activity and stability for oxygen reduction than commercial Pt/C electrocatalysts in alkaline media. This novel strategy opens a new avenue for the synthesis of Co/N-CNTs with great promise for developing high performance and cheap electrocatalysts.
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http://dx.doi.org/10.1039/C8NR00137EDOI Listing
March 2018

A Cationic Diode Based on Asymmetric Nafion Film Deposits.

ACS Appl Mater Interfaces 2017 Mar 16;9(12):11272-11278. Epub 2017 Mar 16.

Department of Chemistry, University of Bath , Claverton Down, Bath BA2 7AY, U.K.

A thin film of Nafion, of approximately 5 μm thickness, asymmetrically deposited onto a 6 μm thick film of poly(ethylene terephthalate) (PET) fabricated with a 5, 10, 20, or 40 μm microhole, is shown to exhibit prominent ionic diode behavior involving cation charge carrier ("cationic diode"). The phenomenon is characterized via voltammetric, chronoamperometric, and impedance methods. Phenomenologically, current rectification effects are comparable to those observed in nanocone devices where space-charge layer effects dominate. However, for microhole diodes a resistive, a limiting, and an overlimiting potential domain can be identified and concentration polarization in solution is shown to dominate in the closed state.
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http://dx.doi.org/10.1021/acsami.7b01774DOI Listing
March 2017

Engineered Graphene Materials: Synthesis and Applications for Polymer Electrolyte Membrane Fuel Cells.

Adv Mater 2017 May 20;29(20). Epub 2016 Dec 20.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, China.

Engineered graphene materials (EGMs) with unique structures and properties have been incorporated into various components of polymer electrolyte membrane fuel cells (PEMFCs) such as electrode, membrane, and bipolar plates to achieve enhanced performances in terms of electrical conductivity, mechanical durability, corrosion resistance, and electrochemical surface area. This research news article provides an overview of the recent development in EGMs and EGM-based PEMFCs with a focus on the effects of EGMs on PEMFC performance when they are incorporated into different components of PEMFCs. The challenges of EGMs for practical PEMFC applications in terms of production scale, stability, conductivity, and coupling capability with other materials are also discussed and the corresponding measures and future research trends to overcome such challenges are proposed.
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http://dx.doi.org/10.1002/adma.201601741DOI Listing
May 2017

Molecularly Rigid Microporous Polyamine Captures and Stabilizes Conducting Platinum Nanoparticle Networks.

ACS Appl Mater Interfaces 2016 Aug 22;8(34):22425-30. Epub 2016 Aug 22.

School of Chemistry, University of Edinburgh , David Brewster Road, Edinburgh EH9 3FJ, U.K.

A molecularly rigid polyamine based on a polymer of intrinsic microporosity (PIM-EA-TB) is shown to capture and stabilize platinum nanoparticles during colloid synthesis in the rigid framework. Stabilization here refers to avoiding aggregation without loss of surface reactivity. In the resulting rigid framework with embedded platinum nanoparticles, the volume ratio of platinum to PIM-EA-TB in starting materials is varied systematically from approximately 1.0 to 0.1 with the resulting platinum nanoparticle diameter varying from approximately 4.2 to 3.1 nm, respectively. Elemental analysis suggests that only a fraction of the polymer is "captured" to give nanocomposites rich in platinum. A transition occurs from electrically conducting and electrochemically active (with shorter average interparticle distance) to nonconducting and only partially electrochemically active (with longer average interparticle distance) polymer-platinum composites. The conducting nanoparticle network in the porous rigid macromolecular framework could be beneficial in electrocatalysis and in sensing applications.
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http://dx.doi.org/10.1021/acsami.6b04144DOI Listing
August 2016

Amorphous nickel boride membrane on a platinum-nickel alloy surface for enhanced oxygen reduction reaction.

Nat Commun 2016 08 9;7:12362. Epub 2016 Aug 9.

Center of Advanced Nanocatalysis (CAN-USTC), University of Science and Technology of China, Hefei 230026 China.

The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.
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http://dx.doi.org/10.1038/ncomms12362DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4980487PMC
August 2016

Ultrathin Icosahedral Pt-Enriched Nanocage with Excellent Oxygen Reduction Reaction Activity.

J Am Chem Soc 2016 Feb 1;138(5):1494-7. Epub 2016 Feb 1.

Center of Advanced Nanocatalysis, University of Science and Technology of China , Hefei, Anhui 230026, China.

Cost-efficient utilization of Pt in the oxygen reduction reaction (ORR) is of great importance for the potential industrial scale demand of proton-exchange membrane fuel cells. Designing a hollow structure of a Pt catalyst offers a great opportunity to enhance the electrocatalytic performance and maximize the use of precious Pt. Herein we report a routine to synthesize ultrathin icosahedral Pt-enriched nanocages. In detail, the Pt atoms were conformally deposited on the surface of Pd icosahedral seeds, followed by selective removal of the Pd core by a concentrated HNO3 solution. The icosahedral Pt-enriched nanocage that is a few atomic layers thick includes the merits of abundant twin defects, an ultrahigh surface/volume ratio, and an ORR-favored Pt{111} facet, all of which have been demonstrated to be promoting factors for ORR. With a 10 times higher specific activity and 7 times higher mass activity, this catalyst shows more extraordinary ORR activity than the commercial Pt/C. The ORR activity of icosahedral Pt-enriched nanocages outperforms the cubic and octahedral nanocages reported in the literature, demonstrating the superiority of the icosahedral nanocage structure.
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http://dx.doi.org/10.1021/jacs.5b12530DOI Listing
February 2016

Platinized Graphene/ceramics Nano-sandwiched Architectures and Electrodes with Outstanding Performance for PEM Fuel Cells.

Sci Rep 2015 Nov 5;5:16246. Epub 2015 Nov 5.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.

For the first time a novel oxygen reduction catalyst with a 3D platinized graphene/nano-ceramic sandwiched architecture is successfully prepared by an unusual method. Herein the specific gravity of graphene nanosheets (GNS) is tailored by platinizing graphene in advance to shorten the difference in the specific gravity between carbon and SiC materials, and then nano-SiC is well intercalated into GNS interlayers. This nano-architecture with highly dispersed Pt nanoparticles exhibits a very high oxygen reduction reaction (ORR) activity and polymer electrolyte membrane (PEM) fuel cell performance. The mass activity of half cells is 1.6 times of that of the GNS supported Pt, and 2.4 times that of the commercial Pt/C catalyst, respectively. Moreover, after an accelerated stress test our catalyst shows a predominantly electrochemical stability compared with benchmarks. Further fuel cell tests show a maximum power density as high as 747 mW/cm(2) at low Pt loading, which is more than 2 times higher than that of fuel cells with the pristine graphene electrode.
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http://dx.doi.org/10.1038/srep16246DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4995351PMC
November 2015

Intrinsically Microporous Polymer Retains Porosity in Vacuum Thermolysis to Electroactive Heterocarbon.

Langmuir 2015 Nov 29;31(44):12300-6. Epub 2015 Oct 29.

Department of Chemistry, University of Bath , Claverton Down, Bath BA2 7AY, United Kingdom.

Vacuum carbonization of organic precursors usually causes considerable structural damage and collapse of morphological features. However, for a polymer with intrinsic microporosity (PIM-EA-TB with a Brunauer-Emmet-Teller (BET) surface area of 1027 m(2)g(-1)), it is shown here that the rigidity of the molecular backbone is retained even during 500 °C vacuum carbonization, yielding a novel type of microporous heterocarbon (either as powder or as thin film membrane) with properties between those of a conducting polymer and those of a carbon. After carbonization, the scanning electron microscopy (SEM) morphology and the small-angle X-ray scattering (SAXS) Guinier radius remain largely unchanged as does the cumulative pore volume. However, the BET surface area is decreased to 242 m(2)g(-1), but microporosity is considerably increased. The new material is shown to exhibit noticeable electrochemical features including two pH-dependent capacitance domains switching from ca. 33 Fg(-1) (when oxidized) to ca. 147 Fg(-1) (when reduced), a low electron transfer reactivity toward oxygen and hydrogen peroxide, and a four-point-probe resistivity (dry) of approximately 40 MΩ/square for a 1-2 μm thick film.
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http://dx.doi.org/10.1021/acs.langmuir.5b02654DOI Listing
November 2015

Hydrogel-derived non-precious electrocatalysts for efficient oxygen reduction.

Sci Rep 2015 Jul 1;5:11739. Epub 2015 Jul 1.

Center of Advanced Nanocatalysis (CAN-USTC), University of Science and Technology of China, Hefei, Anhui 230026, China.

The development of highly active, cheap and robust oxygen reduction reaction (ORR) electrocatalysts to replace precious metal platinum is extremely urgent and challenging for renewable energy devices. Herein we report a novel, green and especially facile hydrogel strategy to construct N and B co-doped nanocarbon embedded with Co-based nanoparticles as an efficient non-precious ORR catalyst. The agarose hydrogel provides a general host matrix to achieve a homogeneous distribution of key precursory components including cobalt (II) acetate and buffer salts, which, upon freeze-drying and carbonization, produces the highly active ORR catalyst. The gel buffer containing Tris base, boric acid and ethylenediaminetetraacetic acid, commonly adopted for pH and ionic strength control, plays distinctively different roles here. These include a green precursor for N- and B-doping, a salt porogen and a Co(2+) chelating agent, all contributing to the excellent ORR activity. This hydrogel-based process is potentially generalizable for many other catalytic materials.
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http://dx.doi.org/10.1038/srep11739DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4486930PMC
July 2015

Carbon-embedded carbon nanotubes as supports of polymer electrolyte membrane fuel cell catalysts.

J Nanosci Nanotechnol 2014 Sep;14(9):6929-33

Carbon shells embedded carbon nanotubes can facilitate Pt nanoparticles loading and dispersing on the core-shell nanostructural support. Carbon shells are prepared by coating polyaniline layers on the core (carbon nanotubes) with in-situ polymerization and subsequent carbonization. The carbon shell embedded carbon nanotube supported Pt catalyst reveals high electrochemical active surface area and mass activity, which are the factors of 1.4 times and 2.2 times higher than that of the pristine carbon nanotube supported Pt, respectively. In addition, the carbon shell embedded carbon nanotube supported Pt catalyst has a higher stability than the carbon nanotube supported Pt catalyst. The improved catalytic activity and stability of our new catalyst can be ascribed to the improved dispersion of Pt nanoparticles on surfaces of carbon nanotubes and the interaction between Pt nanoparticles and carbon shells.
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http://dx.doi.org/10.1166/jnn.2014.8926DOI Listing
September 2014

Nano conductive ceramic wedged graphene composites as highly efficient metal supports for oxygen reduction.

Sci Rep 2014 Feb 5;4:3968. Epub 2014 Feb 5.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.

A novel conductive ceramic/graphene nanocomposite is prepared to prohibit the re-stacking of reduced graphene oxide (RGO) by wedging zirconium diboride (ZrB2) nanoparticles (NPs) into multiple layer nanosheets using a simple solvothermal method. Surprisingly, the RGO/ZrB2 nanocomposite supported Pt NPs shows very excellent catalytic activity. Its electrochemical surface area (ECSA) is up to 148 m(2)g(-1) (very approaches the geometry surface area of 155 m(2)g(-1)), much greater than that of the previous report (usually less than 100 m(2)g(-1)). The mass activity is as high as 16.8 A/g(-1), which is almost 2 times and 5 times that of Pt/RGO (8.6 A/g(-1)) and Pt/C (3.2 A/g(-1)), respectively, as benchmarks. Moreover, after 4000 cycles the catalyst shows only 61% of ECSA loss, meaning a predominantly electrochemical stability. The remarkably improved electrochemical properties with much high Pt utilization of the new catalyst show a promising application in low temperature fuel cells and broader fields.
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http://dx.doi.org/10.1038/srep03968DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913918PMC
February 2014

Direct transformation of amorphous silicon carbide into graphene under low temperature and ambient pressure.

Sci Rep 2013 28;3:1148. Epub 2013 Jan 28.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, PR China.

A large-scale availability of the graphene is critical to the successful application of graphene-based electronic devices. The growth of epitaxial graphene (EG) on insulating silicon carbide (SiC) surfaces has opened a new promising route for large-scale high-quality graphene production. However, two key obstacles to epitaxial growth are extremely high requirements for almost perfectly ordered crystal SiC and harsh process conditions. Here, we report that the amorphous SiC (a-Si(1-x)C(x)) nano-shell (nano-film) can be directly transformed into graphene by using chlorination method under very mild reaction conditions of relative low temperature (800°C) and the ambient pressure in chlorine (Cl(2)) atmosphere. Therefore, our finding, the direct transformation of a-Si(1-x)C(x) into graphene under much milder condition, will open a door to apply this new method to the large-scale production of graphene at low costs.
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http://dx.doi.org/10.1038/srep01148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3556591PMC
July 2013

Highly active platinum nanoparticles on graphene nanosheets with a significant improvement in stability and CO tolerance.

Langmuir 2012 Feb 9;28(8):3979-86. Epub 2012 Feb 9.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, PR China.

Graphene nanosheets (GNS) supporting Pt nanoparticles (PNs) are prepared using perfluorosulfonic acid (PFSA) as a functionalization and anchoring agent. Transmission electron microscope (TEM) results indicate that the prepared Pt NPs are uniformly deposited on GNS with a narrow particle size ranging from 1 to 4 nm in diameter. A high catalytic activity of this novel catalyst is observed by both cyclic voltammetry and oxygen reduction reaction (ORR) measurements due to the increasing of proton (H(+)) transmission channels. Significantly, this novel PFSA-functionalized Pt/GNS (PFSA-Pt/GNS) catalyst reveals a better CO oxidation and lower loss rate of electrochemical active area in comparison with that of the plain Pt/GNS and conventional Pt/C catalysts, indicating our PFSA-Pt/GNS catalysts hold much higher stability and CO tolerance by virtue of introduction of PFSA.
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http://dx.doi.org/10.1021/la2045493DOI Listing
February 2012

Polyaniline-functionalized carbon nanotube supported platinum catalysts.

Langmuir 2011 May 8;27(9):5582-8. Epub 2011 Apr 8.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, People's Republic of China.

Electrocatalytically active platinum (Pt) nanoparticles on a carbon nanotube (CNT) with enhanced nucleation and stability have been demonstrated through introduction of electron-conducting polyaniline (PANI) to bridge the Pt nanoparticles and CNT walls with the presence of platinum-nitride (Pt-N) bonding and π-π bonding. The Pt colloids were prepared through ethanol reduction under the protection of aniline, the CNT was dispersed well with the existence of aniline in the solution, and aniline was polymerized in the presence of a protonic acid (HCl) and an oxidant (NH(4)S(2)O(8)). The synthesized PANI is found to wrap around the CNT as a result of π-π bonding, and highly dispersed Pt nanoparticles are loaded onto the CNT with narrowly distributed particle sizes ranging from 2.0 to 4.0 nm due to the polymer stabilization and existence of Pt-N bonding. The Pt-PANI/CNT catalysts are electroactive and exhibit excellent electrochemical stability and therefore promise potential applications in proton exchange membrane fuel cells.
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http://dx.doi.org/10.1021/la2003589DOI Listing
May 2011
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