1
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Nedzbala HS, Westbroek D, Margavio HRM, Yang H, Noh H, Magpantay SV, Donley CL, Kumbhar AS, Parsons GN, Mayer JM. Photoelectrochemical Proton-Coupled Electron Transfer of TiO 2 Thin Films on Silicon. J Am Chem Soc 2024; 146:10559-10572. [PMID: 38564642 DOI: 10.1021/jacs.4c00014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
TiO2 thin films are often used as protective layers on semiconductors for applications in photovoltaics, molecule-semiconductor hybrid photoelectrodes, and more. Experiments reported here show that TiO2 thin films on silicon are electrochemically and photoelectrochemically reduced in buffered acetonitrile at potentials relevant to photoelectrocatalysis of CO2 reduction, N2 reduction, and H2 evolution. On both n-type Si and irradiated p-type Si, TiO2 reduction is proton-coupled with a 1e-:1H+ stoichiometry, as demonstrated by the Nernstian dependence of the Ti4+/3+ E1/2 on the buffer pKa. Experiments were conducted with and without illumination, and a photovoltage of ∼0.6 V was observed across 20 orders of magnitude in proton activity. The 4 nm films are almost stoichiometrically reduced under mild conditions. The reduced films catalytically transfer protons and electrons to hydrogen atom acceptors, based on cyclic voltammogram, bulk electrolysis, and other mechanistic evidence. TiO2/Si thus has the potential to photoelectrochemically generate high-energy H atom carriers. Characterization of the TiO2 films after reduction reveals restructuring with the formation of islands, rendering TiO2 films as a potentially poor choice as protecting films or catalyst supports under reducing and protic conditions. Overall, this work demonstrates that atomic layer deposition TiO2 films on silicon photoelectrodes undergo both chemical and morphological changes upon application of potentials only modestly negative of RHE in these media. While the results should serve as a cautionary tale for researchers aiming to immobilize molecular monolayers on "protective" metal oxides, the robust proton-coupled electron transfer reactivity of the films introduces opportunities for the photoelectrochemical generation of reactive charge-carrying mediators.
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Affiliation(s)
- Hannah S Nedzbala
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Dalaney Westbroek
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Hannah R M Margavio
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27603, United States
| | - Hyuenwoo Yang
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27603, United States
| | - Hyunho Noh
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Samantha V Magpantay
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Carrie L Donley
- Department of Chemistry, Chapel Hill Analytical and Nanofabrication Laboratory (CHANL), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Amar S Kumbhar
- Department of Chemistry, Chapel Hill Analytical and Nanofabrication Laboratory (CHANL), University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Gregory N Parsons
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27603, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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2
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Huang KY, Yang ZQ, Yang MR, Chen TS, Tang S, Sun WM, Yao Q, Deng HH, Chen W, Xie J. Unraveling a Concerted Proton-Coupled Electron Transfer Pathway in Atomically Precise Gold Nanoclusters. J Am Chem Soc 2024; 146:8706-8715. [PMID: 38487838 DOI: 10.1021/jacs.4c01180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
Metal nanoclusters (MNCs) represent a promising class of materials for catalytic carbon dioxide and proton reduction as well as dihydrogen oxidation. In such reactions, multiple proton-coupled electron transfer (PCET) processes are typically involved, and the current understanding of PCET mechanisms in MNCs has primarily focused on the sequential transfer mode. However, a concerted transfer pathway, i.e., concerted electron-proton transfer (CEPT), despite its potential for a higher catalytic rate and lower reaction barrier, still lacks comprehensive elucidation. Herein, we introduce an experimental paradigm to test the feasibility of the CEPT process in MNCs, by employing Au18(SR)14 (SR denotes thiolate ligand), Au22(SR)18, and Au25(SR)18- as model clusters. Detailed investigations indicate that the photoinduced PCET reactions in the designed system proceed via an CEPT pathway. Furthermore, the rate constants of gold nanoclusters (AuNCs) have been found to be correlated with both the size of the cluster and the flexibility of the Au-S framework. This newly identified PCET behavior in AuNCs is prominently different from that observed in semiconductor quantum dots and plasmonic metal nanoparticles. Our findings are of crucial importance for unveiling the catalytic mechanisms of quantum-confined metal nanomaterials and for the future rational design of more efficient catalysts.
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Affiliation(s)
- Kai-Yuan Huang
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Zhi-Qiang Yang
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Ming-Rui Yang
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Tian-Shui Chen
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Shurong Tang
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Wei-Ming Sun
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Qiaofeng Yao
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Key Laboratory of Organic Integrated Circuits, Ministry of Education, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China
| | - Hao-Hua Deng
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Wei Chen
- Higher Educational Key Laboratory for Nano Biomedical Technology of Fujian Province, Department of Pharmaceutical Analysis, Fujian Medical University, Fuzhou 350004, China
| | - Jianping Xie
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore
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3
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Di Pino S, Donkor ED, Sánchez VM, Rodriguez A, Cassone G, Scherlis D, Hassanali A. ZundEig: The Structure of the Proton in Liquid Water from Unsupervised Learning. J Phys Chem B 2023; 127:9822-9832. [PMID: 37930954 DOI: 10.1021/acs.jpcb.3c06078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
The structure of the excess proton in liquid water has been the subject of lively debate on both experimental and theoretical fronts for the last century. Fluctuations of the proton are typically interpreted in terms of limiting states referred to as the Eigen and Zundel species. Here, we put these ideas under the microscope, taking advantage of recent advances in unsupervised learning that use local atomic descriptors to characterize environments of acidic water combined with advanced clustering techniques. Our agnostic approach leads to the observation of only one charged cluster and two neutral ones. We demonstrate that the charged cluster involving the excess proton is best seen as an ionic topological defect in water's hydrogen bond network, forming a single local minimum on the global free-energy landscape. This charged defect is a highly fluxional moiety, where the idealized Eigen and Zundel species are neither limiting configurations nor distinct thermodynamic states. Instead, the ionic defect enhances the presence of neutral water defects through strong interactions with the network. We dub the combination of the charged and neutral defect clusters as ZundEig, demonstrating that the fluctuations between these local environments provide a general framework for rationalizing more descriptive notions of the proton in the existing literature.
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Affiliation(s)
- Solana Di Pino
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
| | - Edward Danquah Donkor
- International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
| | - Veronica M Sánchez
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
| | - Alex Rodriguez
- International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
- Dipartimento di Matematica e Geoscienze, Universitá degli Studi di Trieste, via Alfonso Valerio 12/1, 34127 Trieste, Italy
| | - Giuseppe Cassone
- Institute for Chemical-Physical Processes, National Research Council (CNR-IPCF), Viale Stagno d'Alcontres 37, 98158 Messina, Italy
| | - Damian Scherlis
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
| | - Ali Hassanali
- International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
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4
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Amorati R, Guo Y, Budhlall BM, Barry CF, Cao D, Challa SSRK. Tandem Hydroperoxyl-Alkylperoxyl Radical Quenching by an Engineered Nanoporous Cerium Oxide Nanoparticle Macrostructure (NCeONP): Toward Efficient Solid-State Autoxidation Inhibitors. ACS OMEGA 2023; 8:40174-40183. [PMID: 37929124 PMCID: PMC10620910 DOI: 10.1021/acsomega.3c03654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 10/05/2023] [Indexed: 11/07/2023]
Abstract
The use of nanomaterials as inhibitors of the autoxidation of organic materials is attracting tremendous interest in petrochemistry, food storage, and biomedical applications. Metal oxide materials and CeO2 in particular represent one of the most investigated inorganic materials with promising radical trapping and antioxidant abilities. However, despite the importance, examples of the CeO2 material's ability to retard the autoxidation of organic substrates are still lacking, together with a plausible chemical mechanism for radical trapping. Herein, we report the synthesis of a new CeO2-derived nanoporous material (NCeONP) with excellent autoxidation inhibiting properties due to its ability to catalyze the cross-dismutation of alkyl peroxyl (ROO•) and hydroperoxyl (HOO•) radicals, generated in the system by the addition of the pro-aromatic hydrocarbon γ-terpinene. The antioxidant ability of NCeONP is superior to that of other nanosized metal oxides, including TiO2, ZnO, ZrO2, and pristine CeO2 nanoparticles. Studies of the reaction with a sacrificial reductant allowed us to propose a mechanism of inhibition consisting of H atom transfer from HOO• to the metal oxides (MOx + HOO• → MOx-H• + O2), followed by the release of the H atom to an ROO• radical (MOx-H• + ROO• → MOx + ROOH). Besides identifying NCeONP as a promising material for developing effective antioxidants, our study provides the first evidence of a radical mechanism that can be exploited to develop novel solid-state autoxidation inhibitors.
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Affiliation(s)
- Riccardo Amorati
- Department
of Chemistry “G. Ciamician”, University of Bologna, Via Gobetti 83, 40129 Bologna, Italy
| | - Yafang Guo
- Department
of Chemistry “G. Ciamician”, University of Bologna, Via Gobetti 83, 40129 Bologna, Italy
| | - Bridgette Maria Budhlall
- Department
of Plastics Engineering, University of Massachusetts
Lowell, Lowell, Massachusetts 01854, United States
| | - Carol Forance Barry
- Department
of Plastics Engineering, University of Massachusetts
Lowell, Lowell, Massachusetts 01854, United States
| | - Dongmei Cao
- Shared
Instrumentation Facility, Louisiana State
University, 121 Chemistry and Material Building, 4048 Highland Rd., Baton Rouge, Louisiana 70809, United States
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5
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Mayer JM. Bonds over Electrons: Proton Coupled Electron Transfer at Solid-Solution Interfaces. J Am Chem Soc 2023; 145:7050-7064. [PMID: 36943755 PMCID: PMC10080693 DOI: 10.1021/jacs.2c10212] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
This Perspective argues that most redox reactions of materials at an interface with a protic solution involve net proton-coupled electron transfer (PCET) (or other cation-coupled ET). This view contrasts with the traditional electron-transfer-focused view of redox reactions at semiconductors, but redox processes at metal surfaces are often described as PCET. Taking a thermodynamic perspective, transfer of an electron is typically accompanied by a stoichiometric proton, much as the chemistry of lithium-ion batteries involves coupled transfers of e- and Li+. The PCET viewpoint implicates the surface-H bond dissociation free energy (BDFE) as the preeminent energetic parameter and its conceptual equivalents, the electrochemical ne-/nH+ potential versus the reversible hydrogen electrode (RHE) and the free energy of hydrogenation, ΔG°H. These parameters capture the thermochemistry of PCET at interfaces better than electronic parameters such as Fermi energies, electron chemical potentials, flat-band potentials, or band-edge energies. A unified picture of PCET at metal and semiconductor surfaces is presented. Exceptions, limitations, implications, and future directions motivated by this approach are described.
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Affiliation(s)
- James M Mayer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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6
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Wu LW, Liu C, Han Y, Yu Y, Liu Z, Huang YF. In Situ Spectroscopic Identification of the Electron-Transfer Intermediates of Photoelectrochemical Proton-Coupled Electron Transfer of Water Oxidation on Au. J Am Chem Soc 2023; 145:2035-2039. [PMID: 36649589 DOI: 10.1021/jacs.2c11882] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Experimental elucidation of the decoupling of electron and proton transfer at a molecular level is essential for thoroughly understanding the kinetics of heterogeneous (photo)electrochemical proton-coupled electron transfer water oxidation. Here we illustrate the electron-transfer intermediates of positively charged surface oxygenated species on Au (Au-OH+) and their correlations with the rate of water oxidation by in situ microphotoelectrochemical surface-enhanced Raman spectroscopy (SERS) and ambient-pressure X-ray photoelectron spectroscopy. At the intermediate stage of water oxidation, a characteristic blue shift of the vibration of Au-OH species in laser-power-density-dependent measurements was assigned to the light-induced production of Au-OH+ in water oxidation. The photothermal effect was excluded according to the vibrational frequencies of Au-OH species as the temperature was increased in a variable-temperature SERS measurement. Density functional theory calculations evidenced that the frequency blue shift is from the positively charged Au-OH species. The photocurrent-dependent frequency blue shift indicated that Au-OH+ is the key electron-transfer intermediate in water oxidation by decoupled electron and proton transfer.
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Affiliation(s)
- Li-Wen Wu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Chiyan Liu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yong Han
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.,Center for Transformative Science, ShanghaiTech University, Shanghai 201210, China
| | - Yi Yu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.,Center for Transformative Science, ShanghaiTech University, Shanghai 201210, China
| | - Zhi Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.,State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.,Center for Transformative Science, ShanghaiTech University, Shanghai 201210, China
| | - Yi-Fan Huang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
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7
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Cooney SE, Fertig AA, Buisch MR, Brennessel WW, Matson EM. Coordination-induced bond weakening of water at the surface of an oxygen-deficient polyoxovanadate cluster. Chem Sci 2022; 13:12726-12737. [PMID: 36519047 PMCID: PMC9645371 DOI: 10.1039/d2sc04843d] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/10/2022] [Indexed: 10/19/2023] Open
Abstract
Hydrogen-atom (H-atom) transfer at the surface of heterogeneous metal oxides has received significant attention owing to its relevance in energy conversion and storage processes. Here, we present the synthesis and characterization of an organofunctionalized polyoxovanadate cluster, (calix)V6O5(OH2)(OMe)8 (calix = 4-tert-butylcalix[4]arene). Through a series of equilibrium studies, we establish the BDFE(O-H)avg of the aquo ligand as 62.4 ± 0.2 kcal mol-1, indicating substantial bond weaking of water upon coordination to the cluster surface. Subsequent kinetic isotope effect studies and Eyring analysis indicate the mechanism by which the hydrogenation of organic substrates occurs proceeds through a concerted proton-electron transfer from the aquo ligand. Atomistic resolution of surface reactivity presents a novel route of hydrogenation reactivity from metal oxide surfaces through H-atom transfer from surface-bound water molecules.
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Affiliation(s)
- Shannon E Cooney
- Department of Chemistry, University of Rochester Rochester NY 14627 USA
| | - Alex A Fertig
- Department of Chemistry, University of Rochester Rochester NY 14627 USA
| | | | | | - Ellen M Matson
- Department of Chemistry, University of Rochester Rochester NY 14627 USA
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8
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Agarwal RG, Mayer JM. Coverage-Dependent Rate-Driving Force Relationships: Hydrogen Transfer from Cerium Oxide Nanoparticle Colloids. J Am Chem Soc 2022; 144:20699-20709. [DOI: 10.1021/jacs.2c07988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Rishi G. Agarwal
- Department of Chemistry, Yale University, New Haven, Connecticut06520-8107, United States
| | - James M. Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut06520-8107, United States
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9
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Medium-independent hydrogen atom binding isotherms of nickel oxide electrodes. Chem 2022. [DOI: 10.1016/j.chempr.2022.08.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Fertig AA, Matson EM. Connecting Thermodynamics and Kinetics of Proton Coupled Electron Transfer at Polyoxovanadate Surfaces Using the Marcus Cross Relation. Inorg Chem 2022; 62:1958-1967. [PMID: 36049052 PMCID: PMC9906739 DOI: 10.1021/acs.inorgchem.2c02541] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Here, we evaluate the efficacy of multiple methods for elucidating the average bond dissociation free energy (BDFE) of two surface hydroxide moieties in a reduced polyoxovanadate cluster, [V6O11(OH)2(TRIOLNO2)2]-2. Through cyclic voltammetry, individual thermochemical parameters describing proton coupled electron transfer (PCET) are obtained, without the need for synthetic isolation of intermediates. Further, we demonstrate that a method involving a series of open circuit potential measurements with varying ratios of reduced to oxidized clusters is most attractive for the direct measurement of BDFE(O-H) for polyoxovanadate clusters as this approach also determines the stoichiometry of PCET. We subsequently connect the driving force of PCET to the rate constant for the transfer of hydrogen atoms to a series of organic substrates through the Marcus cross relation. We show that this method is applicable for the prediction of reaction rates for multielectron/multiproton transfer reactions, extending the findings from previous work focused on single electron/proton reactions.
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11
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Zhao Z, Ling X, El Gabaly F, Grass M, Jabeen N, Jones D, Liu Z, Mun BS, Braun A, Chen Q. Observation of Potential-Induced Hydration on the Surface of Ceramic Proton Conductors Using In Situ Near-Ambient Pressure X-ray Photoelectron Spectroscopy. J Phys Chem Lett 2022; 13:2928-2933. [PMID: 35343700 DOI: 10.1021/acs.jpclett.2c00114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Interactions of ceramic proton conductors with the environment under operating conditions play an essential role on material properties and device performance. It remains unclear how the chemical environment of material, as modulated by the operating condition, affects the proton conductivity. Combining near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy, we investigate the chemical environment changes of oxygen and the conductivity of BaZr0.9Y0.1O3-δ under operating condition. Changes in O 1s core level spectra indicate that adding water vapor pressure increases both hydroxyl groups and active proton sites at undercoordinated oxygen. Applying external potential further promotes this hydration effect, in particular, by increasing the amount of undercoordinated oxygen. The enhanced hydration is accompanied by improved proton conductivity. This work highlights the effects of undercoordinated oxygen for improving the proton conductivity in ceramics.
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Affiliation(s)
- Zihan Zhao
- University of Michigan - Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiao Ling
- University of Michigan - Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Farid El Gabaly
- Sandia National Laboratories, Livermore, California 94551, United States
| | - Michael Grass
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Naila Jabeen
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Nanoscience and Technology Division, National Center for Physics, Quaid-i-Azam University Campus, Islamabad 44000, Pakistan
| | - Deborah Jones
- ICGM, Université Montpellier, CNRS, ENSCM, F-34095 Montpellier cedex 5, France
| | - Zhi Liu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
| | - Bongjin S Mun
- Department of Physics and Photon Science, Gwangju Institute of Science and Technology, Buk-gu Gwangju 500-712, Korea
| | - Artur Braun
- Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
- Hawai'i Natural Energy Institute, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Qianli Chen
- University of Michigan - Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China
- Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
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12
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Warburton RE, Soudackov AV, Hammes-Schiffer S. Theoretical Modeling of Electrochemical Proton-Coupled Electron Transfer. Chem Rev 2022; 122:10599-10650. [PMID: 35230812 DOI: 10.1021/acs.chemrev.1c00929] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Proton-coupled electron transfer (PCET) plays an essential role in a wide range of electrocatalytic processes. A vast array of theoretical and computational methods have been developed to study electrochemical PCET. These methods can be used to calculate redox potentials and pKa values for molecular electrocatalysts, proton-coupled redox potentials and bond dissociation free energies for PCET at metal and semiconductor interfaces, and reorganization energies associated with electrochemical PCET. Periodic density functional theory can also be used to compute PCET activation energies and perform molecular dynamics simulations of electrochemical interfaces. Various approaches for maintaining a constant electrode potential in electronic structure calculations and modeling complex interactions in the electric double layer (EDL) have been developed. Theoretical formulations for both homogeneous and heterogeneous electrochemical PCET spanning the adiabatic, nonadiabatic, and solvent-controlled regimes have been developed and provide analytical expressions for the rate constants and current densities as functions of applied potential. The quantum mechanical treatment of the proton and inclusion of excited vibronic states have been shown to be critical for describing experimental data, such as Tafel slopes and potential-dependent kinetic isotope effects. The calculated rate constants can be used as input to microkinetic models and voltammogram simulations to elucidate complex electrocatalytic processes.
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Affiliation(s)
- Robert E Warburton
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Alexander V Soudackov
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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13
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Ding Z, Goldsmith ZK, Selloni A. Pathways for Electron Transfer at MgO–Water Interfaces from Ab Initio Molecular Dynamics. J Am Chem Soc 2022; 144:2002-2009. [DOI: 10.1021/jacs.1c13250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhutian Ding
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Zachary K. Goldsmith
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Annabella Selloni
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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14
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Peper JL, Gentry NE, Boudy B, Mayer JM. Aqueous TiO 2 Nanoparticles React by Proton-Coupled Electron Transfer. Inorg Chem 2021; 61:767-777. [PMID: 34967207 DOI: 10.1021/acs.inorgchem.1c03125] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Redox reactions of aqueous colloidal TiO2 4 nm nanoparticles (NPs) have been examined, including both citrate-capped and uncapped NPs (c-TiO2 and uc-TiO2). Photoreduction gave stable blue colloidal c-TiO2R NPs with 10-60 electrons per particle. Equilibration of these reduced NPs with soluble redox reagents such as methylviologen (MV2+) provided measurements of the colloid reduction potential as a function of pH. The potentials of c-TiO2 from pH 2-9 varied linearly with pH, with a slope of -60 ± 5 mV/pH. Estimates of the potential at pH 12 were consistent with extrapolating that line to high pH. The reduction potentials did not correlate with the zeta potentials (ζ) or the surface charge of the NPs across this pH range. Similar reduction potentials were observed for c- and uc-TiO2 at low pH even though they have quite different ζ potentials. These results show that the common surface-charging explanation of the pH dependence is not tenable in these systems. Oxidation of reduced c-TiO2R with the electron-transfer oxidant potassium triiodide (KI3) occurred with a significant drop in pH, showing that protons were released when the electrons were removed from the NPs. Smaller pH drops were observed for the proton-coupled electron transfer (PCET) reagents O2 (air) and 4-MeO-TEMPO (4-methoxy-2,2,6,6-tetramethylpiperine-1-oxy radical). The difference in the number of protons released with KI3 vs O2 and 4-MeO-TEMPO was roughly one proton per electron removed. Thus, the thermodynamically preferred reactivity of these colloidal TiO2 NPs is PCET over the pH 2-13 range studied. The measured redox potentials refer to the chemical process TiO2 + H+ + e- → TiO2·e-,H+; and therefore they do not correspond with an electronic energy such as a conduction band edge or flat band potential. The 1e-/1H+ stoichiometry means that the TiO2 reduction potentials correspond to a TiO2-H bond dissociation free energy (BDFE), determined to be 49 ± 2 kcal mol-1. The PCET description is consistent with the pH dependence of E(TiO2/TiO2·e-,H+), the release of protons upon oxidation, the lack of correlation with ζ potentials, the similarity of capped and uncapped NPs, and the small change in the potential and BDFE from the first to the last electron/proton pair (H atom) removed. This behavior is suggested to be the norm for redox-active oxide/water interfaces.
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Affiliation(s)
- Jennifer L Peper
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Noreen E Gentry
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Benjamin Boudy
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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