Publications by authors named "Xia-Guang Zhang"

20 Publications

  • Page 1 of 1

Amplified Interfacial Effect in an Atomically Dispersed RuO -on-Pd 2D Inverse Nanocatalyst for High-Performance Oxygen Reduction.

Angew Chem Int Ed Engl 2021 Jul 9;60(29):16093-16100. Epub 2021 Jun 9.

Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing, College of Materials Science and Engineering, Huaqiao University, Xiamen, 361021, China.

Atomically dispersed oxide-on-metal inverse nanocatalysts provide a blueprint to amplify the strong oxide-metal interactions for heterocatalysis but remain a grand challenge in fabrication. Here we report a 2D inverse nanocatalyst, RuO -on-Pd nanosheets, by in situ creating atomically dispersed RuO /Pd interfaces densely on ultrathin Pd nanosheets via a one-pot synthesis. The product displays unexpected performance toward the oxygen reduction reaction (ORR) in alkaline medium, which represents 8.0- and 22.4-fold enhancement in mass activity compared to the state-of-the-art Pt/C and Pd/C catalysts, respectively, showcasing an excellent Pt-alternative cathode electrocatalyst for fuel cells and metal-air batteries. Density functional theory calculations validate that the RuO /Pd interface can accumulate partial charge from the 2D Pd host and subtly change the adsorption configuration of O to facilitate the O-O bond cleavage. Meanwhile, the d-band center of Pd nanosubstrates is effectively downshifted, realizing weakened oxygen binding strength.
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http://dx.doi.org/10.1002/anie.202104013DOI Listing
July 2021

Light Driven Mechanism of Carbon Dioxide Reduction Reaction to Carbon Monoxide on Gold Nanoparticles: A Theoretical Prediction.

J Phys Chem Lett 2021 Feb 21;12(4):1125-1130. Epub 2021 Jan 21.

State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Insightful understanding of the light driven CO reduction reaction (CORR) mechanism on gold nanoparticles is one of the important issues in the plasmon mediated photocatalytic study. Herein, time-dependent density functional theory and reduced two-state model are adopted to investigate the photoinduced charge transfer in interfaces. According to the excitation energy and orbital coupling, the light driven mechanism of CORR on gold nanoparticles can be described as follows: the light induces electron excitation and then transfers to the physisorbed CO, and CO can relax to a bent structure adsorbed on gold nanoparticles, and the adsorbed C-O bonds are dissociated finally. Moreover, our calculated results demonstrate that the s, p, and d electron excitations of gold nanoparticles are the major contribution for the CO adsorption and the C-O dissociation process, respectively. This work would promote the understanding of the light driven electron transfer and photocatalytic CORR on the noble metal.
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http://dx.doi.org/10.1021/acs.jpclett.0c03694DOI Listing
February 2021

Molecular Insight of the Critical Role of Ni in Pt-Based Nanocatalysts for Improving the Oxygen Reduction Reaction Probed Using an SERS Borrowing Strategy.

J Am Chem Soc 2021 Jan 15;143(3):1318-1322. Epub 2021 Jan 15.

College of Energy, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, College of Materials, iChEM, Xiamen University, Xiamen 361005, China.

PtNi alloy catalysts have excellent catalytic activity and are considered some of the most promising electrocatalysts capable of replacing pure Pt for the oxygen reduction reaction (ORR). For PtNi alloys, Ni-doping can improve performance by changing the electronic and structural properties of the catalyst surface and its interaction with reaction intermediates. However, to date there is no direct spectral evidence detecting or identifying the effect of Ni on the ORR in PtNi alloy catalysts. Herein, we introduce a surface-enhanced Raman spectroscopic (SERS) "borrowing" strategy for investigating ORR processes catalyzed by [email protected] nanoparticles (NPs). The bond vibration of adsorbed peroxide intermediate species (*OOH) was obtained, and the effect of Ni on the interaction between surface Pt and *OOH was studied by varying the Ni content in the alloy. The frequency of the *OOH spectral band has an obvious red-shift with increasing Ni content. Combined with density functional theory (DFT) calculations, we show that Ni-doping can optimize *OOH surface binding on the Pt surface, achieving more efficient electron transfer, thus improving the ORR rate. Notably, these results evidence the SERS borrowing strategy as an effective technique for observations of catalytic processes.
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http://dx.doi.org/10.1021/jacs.0c12755DOI Listing
January 2021

Spectroscopic Verification of Adsorbed Hydroxy Intermediates in the Bifunctional Mechanism of the Hydrogen Oxidation Reaction.

Angew Chem Int Ed Engl 2021 Mar 29;60(11):5708-5711. Epub 2021 Jan 29.

State Key Laboratory of Physical Chemistry of Solid Surfaces,iChEM, College of Chemistry and Chemical Engineering, College of Energy, Xiamen University, Xiamen, 361005, China.

Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion-exchange-membrane fuel cells. However, uncertainty remains around the alkaline HOR mechanism owing to a lack of direct in situ evidence of intermediates. In this study, in situ electrochemical surface-enhanced Raman spectroscopy (SERS) and DFT were used to study HOR processes on PtNi alloy and Pt surfaces, respectively. Spectroscopic evidence indicates that adsorbed hydroxy species (OH ) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OH species were not observed on the Pt surface during the HOR. We show that Ni doping promoted hydroxy adsorption on the platinum-alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxy adsorption. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity.
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http://dx.doi.org/10.1002/anie.202015571DOI Listing
March 2021

Selective Fabrication of Single-Molecule Junctions by Interface Engineering.

Small 2020 Dec 5;16(48):e2004720. Epub 2020 Nov 5.

Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering and State Key Laboratory of Physical Chemistry of Solid Surfaces, IKKEM, iChEM, Xiamen University, Xiamen, 361005, China.

Recent progress in addressing electrically driven single-molecule behaviors has opened up a path toward the controllable fabrication of molecular devices. Herein, the selective fabrication of single-molecule junctions is achieved by employing the external electric field. For molecular junctions with methylthio (-SMe), thioacetate (-SAc), amine (-NH ), and pyridyl (-PY), the evolution of their formation probabilities along with the electric field is extracted from the plateau analysis of individual single-molecule break junction traces. With the increase of the electric field, the SMe-anchored molecules show a different trend in the formation probability compared to the other molecular junctions, which is consistent with the density functional theory calculations. Furthermore, switching from an SMe-anchored junction to an SAc-anchored junction is realized by altering the electric field in a mixed solution. The results in this work provide a new approach to the controllable fabrication and modulation of single-molecule junctions and other bottom-up nanodevices at molecular scales.
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http://dx.doi.org/10.1002/smll.202004720DOI Listing
December 2020

Electroreduction Reaction Mechanism of Carbon Dioxide to C Products via Cu/Au Bimetallic Catalysis: A Theoretical Prediction.

J Phys Chem Lett 2020 Aug 3;11(16):6593-6599. Epub 2020 Aug 3.

State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Understanding the bimetallic interfacial effects on the catalytic CO reduction reaction (CORR) is an important and challenging issue. Herein, the geometric structure, electronic structure, and electrocatalytic property of Cu(submonolayer)/Au bimetallic interfaces are investigated by using density functional theory calculation. The results predict that the expansion of the Cu lattice can significantly modulate the CORR performance, the Cu(submonolayer)/Au interface has good surface activity promoting the reduction of CO to C compounds, and the final products of CORR on Cu/Au(111) and Cu/Au(100) surfaces are ethanol and a mixture of ethanol and ethylene, respectively. Furthermore, with regard to surface coverage and adsorption energy being two essential parameters for CORR, we demonstrate that the reaction of *CO and *CHO is the key process for obtaining the C products on the Cu/Au interface. This study offers a useful strategy for improving the surface activity and selectivity for CORR.
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http://dx.doi.org/10.1021/acs.jpclett.0c01970DOI Listing
August 2020

Multiregion Janus-Featured Cobalt Phosphide-Cobalt Composite for Highly Reversible Room-Temperature Sodium-Sulfur Batteries.

ACS Nano 2020 Aug 30;14(8):10284-10293. Epub 2020 Jul 30.

Institute for Superconducting and Electronic Materials, University of Wollongong, Innovation Campus, Squires Way, North Wollongong, New South Wales 2500, Australia.

Electrode materials with high conductivity, strong chemisorption, and catalysis toward polysulfides are recognized as key factors for metal-sulfur batteries. Nevertheless, the construction of such functional material is a challenge for room-temperature sodium-sulfur (RT-Na/S) batteries. Herein, a multiregion Janus-featured CoP-Co structure obtained sequential carbonization-oxidation-phosphidation of heteroseed zeolitic imidazolate frameworks is introduced. The structural virtues include a heterostructure existing in a CoP-Co structure and a conductive network of N-doped porous carbon nanotube hollow cages (NCNHCs), endowing it with superior conductivity in both the short- and long-range and strong polarity toward polysulfides. Thus, the [email protected]/NCNHC cathode exhibits superior electrochemical performance (448 mAh g remained for 700 times cycling under 1 A g) and an optimized redox mechanism in polysulfides conversion. Density functional theory calculations present that the CoP-Co structure optimizes bond structure and bandwidth, whereas the pure CoP is lower than the corresponding Fermi level, which could essentially benefit the adsorptive capability and charge transfer from the CoP-Co surface to NaS and therefore improve its affinity to polysulfides.
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http://dx.doi.org/10.1021/acsnano.0c03737DOI Listing
August 2020

Probing Electric Field Distributions in the Double Layer of a Single-Crystal Electrode with Angstrom Spatial Resolution using Raman Spectroscopy.

J Am Chem Soc 2020 Jul 23;142(27):11698-11702. Epub 2020 Jun 23.

State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, College of Energy, Xiamen University, Xiamen 361005, China.

The electrical double layer (EDL) is the extremely important interfacial region involved in many electrochemical reactions, and it is the subject of significant study in electrochemistry and surface science. However, the direct measurement of interfacial electric fields in the EDL is challenging. In this work, both electrochemical resonant Raman spectroscopy and theoretical calculations were used to study electric field distributions in the EDL of an atomically flat single-crystal Au(111) electrode with self-assembled monolayer molecular films. This was achieved using a series of redox-active molecules containing the 4,4'-bipyridinium moiety as a Raman marker that were located at different precisely controlled distances away from the electrode surface. It was found that the electric field and the dipole moment of the probe molecule both directly affected its Raman signal intensity, which in turn could be used to map the electric field distribution at the interface. Also, by variation of the electrolyte anion concentration, the Raman intensity was found to decrease when the electric field strength increased. Moreover, the distance between adjacent Raman markers was ∼2.1 Å. Thus, angstrom-level spatial resolution in the mapping of electric field distributions at the electrode-electrolyte interface was realized. These results directly evidence the EDL structure, bridging the gap between the theoretical and experimental understandings of the interface.
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http://dx.doi.org/10.1021/jacs.0c05162DOI Listing
July 2020

Probing the Local Generation and Diffusion of Active Oxygen Species on a Pd/Au Bimetallic Surface by Tip-Enhanced Raman Spectroscopy.

J Am Chem Soc 2020 Jan 10;142(3):1341-1347. Epub 2020 Jan 10.

Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 361005 , China.

Active oxygen species (AOS) play key roles in many important catalytic reactions relevant to clean energy and environment. However, it remains challenging to characterize the active sites for producing AOS and to image the surface properties of AOS, especially on multicomponent metallic catalyst surfaces. Herein, we utilize tip-enhanced Raman spectroscopy (TERS) to probe the local generation and diffusion of OH radicals on a Pd/Au(111) bimetallic catalyst surface. The reactive OH radicals can be catalytically generated from hydrogen peroxide (HO) at the metal surface, which then oxidizes the surface adsorbed thiolate, a reactant that is used as the TERS probe. By TERS imaging of the spatial distribution of unreacted thiolate molecules, we demonstrate that the Pd surface is active for generation of OH radicals and the Pd step edge shows much higher activity than the Pd terrace, whereas the Au surface is inactive. Furthermore, we find that the locally generated OH radicals at the Pd step edge could diffuse to both the Au and the Pd surface sites to induce oxidative reactions, with a diffusion length estimated to be about 5.4 nm. Our TERS imaging with few-nanometer spatial resolution not only unravels the active sites but also characterizes in real space the diffusion behavior of OH radicals. The results are highly valuable to understand AOS-triggered catalytic reactions. The strategy of using reactants with large Raman cross sections as TERS probes may broaden the application of TERS for studying catalysis with reactive small molecules.
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http://dx.doi.org/10.1021/jacs.9b10512DOI Listing
January 2020

Single-Molecule Measurement of Adsorption Free Energy at the Solid-Liquid Interface.

Angew Chem Int Ed Engl 2019 Oct 30;58(41):14534-14538. Epub 2019 Aug 30.

Pen-Tung Sah Institute of Micro-Nano Science and Technology, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering,iChEM, Xiamen University, Xiamen, 361005, China.

Adsorption plays a critical role in surface and interface processes. Fractional surface coverage and adsorption free energy are two essential parameters of molecular adsorption. However, although adsorption at the solid-gas interface has been well-studied, and some adsorption models were proposed more than a century ago, challenges remain for the experimental investigation of molecular adsorption at the solid-liquid interface. Herein, we report the statistical and quantitative single-molecule measurement of adsorption at the solid-liquid interface by using the single-molecule break junction technique. The fractional surface coverage was extracted from the analysis of junction formation probability so that the adsorption free energy could be calculated by referring to the Langmuir isotherm. In the case of three prototypical molecules with terminal methylthio, pyridyl, and amino groups, the adsorption free energies were found to be 32.5, 33.9, and 28.3 kJ mol , respectively, which are consistent with DFT calculations.
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http://dx.doi.org/10.1002/anie.201907966DOI Listing
October 2019

Interfacial Construction of Plasmonic Nanostructures for the Utilization of the Plasmon-Excited Electrons and Holes.

J Am Chem Soc 2019 May 13;141(20):8053-8057. Epub 2019 May 13.

State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering , Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Xiamen University , Xiamen 361005 , China.

Surface plasmons (SPs) are able to promote chemical reactions through the participation of the energetic charge carriers produced following plasmons decay. Using p-aminothiophenol (PATP) as a probe molecule, we used surface-enhanced Raman spectroscopy to follow the progress of its transformation, in situ, to investigate systematically the role of hot electrons and holes. The energetic carrier mediated PATP oxidation was found to occur even in the absence of oxygen, and was greatly influenced by the interface region near the gold surface. The observed reaction, which occurred efficiently on [email protected] nanostructures, did not happen on bare gold nanoparticles (NPs) or core-shell nanostructures when a silicon oxide layer blocked access to the gold. Moreover, the product of the PATP oxidation with oxygen on [email protected] nanostructures differed from what was obtained without oxygen, suggesting that the mechanism through which "hot holes" mediated the oxidation reaction was different from that operating with oxygen activated by hot electrons.
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http://dx.doi.org/10.1021/jacs.9b02518DOI Listing
May 2019

Stable Na Plating and Stripping Electrochemistry Promoted by In Situ Construction of an Alloy-Based Sodiophilic Interphase.

Adv Mater 2019 Apr 27;31(16):e1807495. Epub 2019 Feb 27.

State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, P. R. China.

Sodium metal anodes are poor due to the reversibility of Na plating/stripping, which hinders their practical applications. A strategy to form a sodiophilic Au-Na alloy interphase on a Cu current collector, involving a sputtered Au thin layer, is shown to enable efficient Na plating/stripping for a certain period of time. Herein, electrochemical behaviors of Na plating on different substrates are explored, and it is revealed that the sodiophilic interphase can be achieved universally by in situ formation of M-Na (M = Au, Sn, and Sb) alloys during Na plating prior to Na bulk deposition in the initial cycle. Moreover, it is found that repetitive alloying-dealloying leads to falling-off of thin film sodiophilic materials and thus limits the lifespan of efficient Na cycling. Therefore, an approach is further developed by employing particles of sodiophilic materials combined with the control over the cutoff potential, which significantly improves the stability of Na plating/stripping process. Especially, the low-cost [email protected] and [email protected] composite current collectors allow Na plating and stripping to cycle for 2000 and 1700 times with the average efficiency of 99.9% at 2 mA cm .
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http://dx.doi.org/10.1002/adma.201807495DOI Listing
April 2019

Promoting electrocatalytic CO reduction to formate via sulfur-boosting water activation on indium surfaces.

Nat Commun 2019 02 21;10(1):892. Epub 2019 Feb 21.

State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, National Engineering Laboratory for Green Chemical Productions of Alcohols, Ethers and Esters, College of Chemistry and Chemical Engineering, Xiamen University, 361005, Xiamen, China.

Electrocatalytic reduction of CO to fuels and chemicals is one of the most attractive routes for CO utilization. Current catalysts suffer from low faradaic efficiency of a CO-reduction product at high current density (or reaction rate). Here, we report that a sulfur-doped indium catalyst exhibits high faradaic efficiency of formate (>85%) in a broad range of current density (25-100 mA cm) for electrocatalytic CO reduction in aqueous media. The formation rate of formate reaches 1449 μmol h cm with 93% faradaic efficiency, the highest value reported to date. Our studies suggest that sulfur accelerates CO reduction by a unique mechanism. Sulfur enhances the activation of water, forming hydrogen species that can readily react with CO to produce formate. The promoting effect of chalcogen modifiers can be extended to other metal catalysts. This work offers a simple and useful strategy for designing both active and selective electrocatalysts for CO reduction.
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http://dx.doi.org/10.1038/s41467-019-08805-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6385284PMC
February 2019

Lithiophilic Faceted Cu(100) Surfaces: High Utilization of Host Surface and Cavities for Lithium Metal Anodes.

Angew Chem Int Ed Engl 2019 Mar 21;58(10):3092-3096. Epub 2019 Jan 21.

State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.

Lithium metal anodes suffer from poor cycling stability and potential safety hazards. To alleviate these problems, Li thin-film anodes prepared on current collectors (CCs) and Li-free types of anodes that involve direct Li plating on CCs have received increasing attention. In this study, the atomic-scale design of Cu-CC surface lithiophilicity based on surface lattice matching of the bcc Li(110) and fcc Cu(100) faces as well as electrochemical achievement of Cu(100)-preferred surfaces for smooth Li deposition with a low nucleation barrier is reported. Additionally, a purposely designed solid-electrolyte interphase is created for Li anodes prepared on CCs. Not only is a smooth planar Li thin film prepared, but a uniform Li plating/stripping on the skeleton of 3D CCs is achieved as well by high utilization of the surface and cavities of the 3D CCs. This work demonstrates surface electrochemistry approaches to construct stable Li metal-electrolyte interphases towards practical applications of Li anodes prepared on CCs.
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http://dx.doi.org/10.1002/anie.201812523DOI Listing
March 2019

Real-Space Observation of Atomic Site-Specific Electronic Properties of a Pt Nanoisland/Au(111) Bimetallic Surface by Tip-Enhanced Raman Spectroscopy.

Angew Chem Int Ed Engl 2018 Oct 11;57(40):13177-13181. Epub 2018 Sep 11.

Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), State Key Laboratory of Physical Chemistry of Solid Surfaces, The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.

Resolving atomic site-specific electronic properties and correlated substrate-molecule interactions is challenging in real space. Now, mapping of sub-10 nm sized Pt nanoislands on a Au(111) surface was achieved by tip-enhanced Raman spectroscopy, using the distinct Raman fingerprints of adsorbed 4-chlorophenyl isocyanide molecules. A spatial resolution better than 2.5 nm allows the electronic properties of the terrace, step edge, kink, and corner sites with varying coordination environments to be resolved in real space in one Pt nanoisland. Calculations suggest that low-coordinate atomic sites have a higher d-band electronic profile and thus stronger metal-molecule interactions, leading to the observed blue-shift of Raman frequency of the N≡C bond of adsorbed molecules. An experimental and theoretical study on Pt(111) and mono- and bi-atomic layer Pt nanoislands on a Au(111) surface reveals the bimetallic effect that weakens with the increasing number of deposited Pt adlayer.
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http://dx.doi.org/10.1002/anie.201807778DOI Listing
October 2018

Boosting Formate Production in Electrocatalytic CO Reduction over Wide Potential Window on Pd Surfaces.

J Am Chem Soc 2018 02 20;140(8):2880-2889. Epub 2018 Feb 20.

Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Department of Chemistry, Fudan University , Shanghai 200433, P. R. China.

Facile interconversion between CO and formate/formic acid (FA) is of broad interest in energy storage and conversion and neutral carbon emission. Historically, electrochemical CO reduction reaction to formate on Pd surfaces was limited to a narrow potential range positive of -0.25 V (vs RHE). Herein, a boron-doped Pd catalyst (Pd-B/C), with a high CO tolerance to facilitate dehydrogenation of FA/formate to CO, is initially explored for electrochemical CO reduction over the potential range of -0.2 V to -1.0 V (vs RHE), with reference to Pd/C. The experimental results demonstrate that the faradaic efficiency for formate (η) reaches ca. 70% over 2 h of electrolysis in CO-saturated 0.1 M KHCO at -0.5 V (vs RHE) on Pd-B/C, that is ca. 12 times as high as that on homemade or commercial Pd/C, leading to a formate concentration of ca. 234 mM mg Pd, or ca. 18 times as high as that on Pd/C, without optimization of the catalyst layer and the electrolyte. Furthermore, the competitive selectivity ηη on Pd-B/C is always significantly higher than that on Pd/C despite a decreases of η and an increases of the CO faradaic efficiency (η) at potentials negative of -0.5 V. The density functional theory (DFT) calculations on energetic aspects of CO reduction reaction on modeled Pd(111) surfaces with and without H-adsorbate reveal that the B-doping in the Pd subsurface favors the formation of the adsorbed HCOO*, an intermediate for the FA pathway, more than that of *COOH, an intermediate for the CO pathway. The present study confers Pd-B/C a unique dual functional catalyst for the HCOOH ↔ CO interconversion.
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http://dx.doi.org/10.1021/jacs.7b12506DOI Listing
February 2018

Plasmon-Enhanced Ultrasensitive Surface Analysis Using Ag Nanoantenna.

Anal Chem 2018 02 10;90(3):2018-2022. Epub 2018 Jan 10.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University , Xiamen 361005, China.

Raman scattering and fluorescence spectroscopy permeate analytic science and are featured in the plasmon-enhanced spectroscopy (PES) family. However, the modest enhancement of plasmon-enhanced fluorescence (PEF) significantly limits the sensitivity in surface analysis and material characterization. Herein, we report a Ag nanoantenna platform, which simultaneously fulfills very strong emission (an optimum average enhancement of 10-fold) and an ultrafast emission rate (∼280-fold) in PES. For applications in surface science, this platform has been examined with a diverse array of fluorophores. Meanwhile, we utilized a finite-element method (FEM) and time-dependent density functional theory (TD-DFT) to comprehensively investigate the mechanism of largely enhanced radiative decay. PES with a shell-isolated Ag nanoantenna will open a wealth of advanced scenarios for ultrasensitive surface analysis.
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http://dx.doi.org/10.1021/acs.analchem.7b04113DOI Listing
February 2018

Revealing the Role of Interfacial Properties on Catalytic Behaviors by in Situ Surface-Enhanced Raman Spectroscopy.

J Am Chem Soc 2017 08 25;139(30):10339-10346. Epub 2017 Jul 25.

MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, and ‡Department of Physics, Research Institute for Biomimetics and Soft Matter, Xiamen University , Xiamen 361005, China.

Insightful understanding of how interfacial structures and properties affect catalytic processes is one of the most challenging issues in heterogeneous catalysis. Here, the essential roles of Pt-Au and Pt-oxide-Au interfaces on the activation of H and the hydrogenation of para-nitrothiophenol (pNTP) were studied at molecular level by in situ surface-enhanced Raman spectroscopy (SERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Pt-Au and Pt-oxide-Au interfaces were fabricated through the synthesis of Pt-on-Au and Pt-on-SHINs nanocomposites. Direct spectroscopic evidence demonstrates that the atomic hydrogen species generated on the Pt nanocatalysts can spill over from Pt to Au via the Pt-Au and Pt-TiO-Au interfaces, but would be blocked at the Pt-SiO-Au interfaces, leading to the different reaction pathways and product selectivity on Pt-on-Au and Pt-on-SHINs nanocomposites. Such findings have also been verified by the density functional theory calculation. In addition, it is found that nanocatalysts assembled on pinhole-free shell-isolated nanoparticles (Pt-on-pinhole-free-SHINs) can override the influence of the Au core on the reaction and can be applied as promising platforms for the in situ study of heterogeneous catalysis. This work offers a concrete example of how SERS/SHINERS elucidate details about in situ reaction and helps to dig out the fundamental role of interfaces in catalysis.
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http://dx.doi.org/10.1021/jacs.7b04011DOI Listing
August 2017

Competing Mechanisms in the Acetaldehyde Functionalization of Positively Charged Hydrogenated Silicene.

Chemphyschem 2017 Feb 19;18(3):281-286. Epub 2016 Dec 19.

State Key Laboratory of Physical Chemistry of Solid Surface and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, No.422, Siming South Road, Xiamen, 361005, Fujian, P.R. China.

Density functional theory calculations were used to elucidate the mechanism of the addition reaction of acetaldehyde to positively charged hydrogenated silicene (H-silicene). We found that the positively charged H-silicene plane could be partially restructured to form a vacant Si site, which enabled an additional nucleophilic addition reaction. After attachment of the acetaldehyde molecule to the H-silicene plane, two competing pathways were found to be involved in the hydrogen-abstraction process: a random-reaction mechanism and a chain-reaction mechanism. The theoretical results provided detailed information about stable structures and thermodynamic parameters of the reaction pathways, such as equilibrium geometries, Gibbs free energies, and the evolution of the spin densities and atomic charges. Our results reveal that the existence of a positive charge can significantly activate the grafting of unsaturated species on hydrogenated silicene, even if no silicon dangling bond is created proactively. The simulated Raman spectra of the two products were analyzed to elucidate the features of the competing mechanisms.
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http://dx.doi.org/10.1002/cphc.201601013DOI Listing
February 2017

Alkyne-Modulated Surface-Enhanced Raman Scattering-Palette for Optical Interference-Free and Multiplex Cellular Imaging.

Anal Chem 2016 06 27;88(12):6115-9. Epub 2016 May 27.

Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University , Wuhan 430072, P. R. China.

The alkyne tags possess unique interference-free Raman emissions but are still hindered for further application in the field of biochemical labels due to its extremely weak spontaneous Raman scattering. With the aid of computational chemistry, herein, an alkyne-modulated surface-enhanced Raman scattering (SERS) palette is constructed based on rationally designed 4-ethynylbenzenethiol derivatives for spectroscopic signature, [email protected] core for optical enhancement and an encapsulating polyallylamine shell for protection and conjugation. Even for the pigment rich plant cell (e.g., pollen), the alkyne-coded SERS tag can be highly discerned on two-dimension distribution impervious to strong organic interferences originating from resonance-enhanced Raman scattering or autofluorescence. In addition, the alkynyl-containing Raman reporters contribute especially narrow emission, band shift-tunable (2100-2300 cm(-1)) and tremendously enhanced Raman signals when the alkynyl group locates at para position of mercaptobenzene ring. Depending on only single Raman band, the suggested alkyne-modulated SERS-palette potentially provides a more effective solution for multiplex cellular imaging with vibrant colors, when the hyperspectral and fairly intense optical noises originating from lower wavenumber region (<1800 cm(-1)) are inevitable under complex ambient conditions.
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http://dx.doi.org/10.1021/acs.analchem.6b01374DOI Listing
June 2016
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