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Green synthesis and characterization of binary, ternary, and quaternary Ti/MMO anodes for chlorine and oxygen evolution reactions. Sci Rep 2024; 14:9821. [PMID: 38684728 PMCID: PMC11058822 DOI: 10.1038/s41598-024-59595-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Accepted: 04/12/2024] [Indexed: 05/02/2024] Open
Abstract
Dimensionally stable anodes of titanium (Ti) metal coated with mixed metal oxides (MMO) are widely used in several electrochemical applications, especially chloro-alkali electrolysis. Herein, we deposited MMO coatings on Ti substrates in different compositions, namely, (60%RuO2-40%TiO2), (60%RuO2-30%TiO2-10%IrO2), and (60%RuO2-20%TiO2-15%IrO2-5%Ta2O5), where RuO2 has the same percentage ratio in all coatings. The aim was to use these electrodes for chlorine evolution reaction (CER) and oxygen evolution reaction (OER) applications. Electrochemical characterization of the coated samples was performed to identify the best Ti/MMO electrodes with the highest efficiencies among the various prepared combinations. The role of IrO2 and Ta2O5 in enhancing corrosion resistance and electrochemical efficacy was up for debate. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were exploited to determine the surface morphology, chemical composition, crystallinity, surface composition, and chemical states of the acquired coatings. The differential scanning calorimetry (DSC) method was used to evaluate the apparent activation energy ( E a ) of the deposited MMO. Additionally, the electrochemical performance of our designed coatings was scrutinized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), a current on-off test, a CV stability test (ST), and an accelerated stability test (AST). Furthermore, linear sweep voltammetry (LSV) was incorporated to assess the catalytic efficacy of the prepared anodes toward the CER in a brine solution of pH 2 and the OER in 1 M H2SO4. It became clear that the CER and OER incurred almost the same potential value (1.1 V) on both Ti/RuO2-TiO2 and Ti/RuO2-TiO2-IrO2 electrodes. However, on the Ti/RuO2-TiO2-IrO2-Ta2O5 anode, there was a 0.2 V potential difference between the CER occurring at 1.1 V and the OER happening at 1.3 V.
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PiNNwall: Heterogeneous Electrode Models from Integrating Machine Learning and Atomistic Simulation. J Chem Theory Comput 2023; 19:5199-5209. [PMID: 37477645 PMCID: PMC10413855 DOI: 10.1021/acs.jctc.3c00359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Indexed: 07/22/2023]
Abstract
Electrochemical energy storage always involves the capacitive process. The prevailing electrode model used in the molecular simulation of polarizable electrode-electrolyte systems is the Siepmann-Sprik model developed for perfect metal electrodes. This model has been recently extended to study the metallicity in the electrode by including the Thomas-Fermi screening length. Nevertheless, a further extension to heterogeneous electrode models requires introducing chemical specificity, which does not have any analytical recipes. Here, we address this challenge by integrating the atomistic machine learning code (PiNN) for generating the base charge and response kernel and the classical molecular dynamics code (MetalWalls) dedicated to the modeling of electrochemical systems, and this leads to the development of the PiNNwall interface. Apart from the cases of chemically doped graphene and graphene oxide electrodes as shown in this study, the PiNNwall interface also allows us to probe polarized oxide surfaces in which both the proton charge and the electronic charge can coexist. Therefore, this work opens the door for modeling heterogeneous and complex electrode materials often found in energy storage systems.
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Electrokinetic behavior of artificial and natural calcites: A review of experimental measurements and surface complexation models. Adv Colloid Interface Sci 2022; 301:102600. [PMID: 35065336 DOI: 10.1016/j.cis.2022.102600] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 01/06/2022] [Accepted: 01/09/2022] [Indexed: 11/28/2022]
Abstract
The surface charge of calcite in aqueous environments is essential to many industrial and environmental applications. Electrokinetic measurements are usually used to assess the calcite charging behavior and characterize its electrical double layer (EDL). Numerous surface complexation models (SCMs) have been proposed to interpret the effect of different surface interactions on the zeta potential. Because of their versatility, SCMs have also become important tools in reactive transport modeling. The research on enhanced oil recovery within the last decade has led to an increased number of publications reporting both zeta potential measurements and SCMs for calcite. Nonetheless, the measurements are often inconsistent and the reasons for choosing one model over another are unclear. In this work, we review the models proposed for calcite and address their main differences. We first collect a large number of published zeta potential measurements and then we fit a Diffuse Layer, Basic Stern, and Charge-Distribution Multi-Site Complexation models to a selected reliable dataset. For each model, we maintain a similar number of adjustable parameters. After optimizing the parameters of the models, we systematically compare their prediction capabilities against data obtained in monovalent and divalent electrolyte systems containing calcium, magnesium, sulfate, or carbonate. We show that, often, the discrepancies between the models and the experimental data can be explained by different levels of disequilibrium. Nonetheless, assumptions used in the development of the models may significantly reduce their extrapolability to variable chemical conditions. The poor agreement between the models tuned to electrokinetic data with surface charge measurements and dynamic retention from single-phase flowthrough tests show that zeta potential may not be the best type of data to characterize ion binding at the calcite surface. Including the effect of mineral impurities and temperature on the calcite surface speciation and electrokinetic behavior prevail as main challenges for reactive transport modeling.
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Modern applications of scanning electrochemical microscopy in the analysis of electrocatalytic surface reactions. CHINESE JOURNAL OF CATALYSIS 2022. [DOI: 10.1016/s1872-2067(21)63948-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Origin of Asymmetric Electric Double Layers at Electrified Oxide/Electrolyte Interfaces. J Phys Chem Lett 2021; 12:4616-4622. [PMID: 33973792 PMCID: PMC8154876 DOI: 10.1021/acs.jpclett.1c00775] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The structure of electric double layers (EDLs) dictates the chemistry and the physics of electrified interfaces, and the differential capacitance is the key property for characterizing EDLs. Here we develop a theoretical model for computing the differential Helmholtz capacitance CH of oxide-electrolyte interfaces using density functional theory-based finite-field molecular dynamics simulations. It is found that the dipole of interfacial adsorbed groups (i.e., water molecule, hydroxyl ion, and proton) at the electrified SnO2(110)/NaCl interfaces significantly modulates the double layer potential which leads to the asymmetric distribution of CH. We also find that the dissociative water adsorption prefers the inner sphere binding of counterions, which in turn leads to a higher Helmholtz capacitance, compared with that of the nondissociative case at the interface. This work provides a molecular interpretation of asymmetric EDLs seen experimentally in a range of metal oxides/hydroxides.
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Effects of temperature and heating method on the performance of Ti/Ru0.25Ir0.25Ti0.50O2 anodes applied toward Bisphenol S removal. Electrochim Acta 2020. [DOI: 10.1016/j.electacta.2020.137273] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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8
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Measurement of powdery oxygen evolution reaction catalyst under practical current density using pressure-bonded electrodes. Electrochim Acta 2020. [DOI: 10.1016/j.electacta.2020.136544] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Computing Surface Acidity Constants of Proton Hopping Groups from Density Functional Theory-Based Molecular Dynamics: Application to the SnO 2(110)/H 2O Interface. J Chem Theory Comput 2020; 16:6520-6527. [PMID: 32794753 DOI: 10.1021/acs.jctc.0c00021] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton transfer at metal oxide/water interfaces plays an important role in electrochemistry, geochemistry, and environmental science. The key thermodynamic quantity to characterize this process is the surface acidity constant. An ab initio method that combines density functional theory-based molecular dynamics (DFTMD) and free energy perturbation theory has been established for computing surface acidity constants. However, it involves a reversible proton insertion procedure in which frequent proton hopping, e.g., for strong bases and some oxide surfaces (e.g., SnO2), can cause instability issues in electronic structure calculation. In the original implementation, harmonic restraining potentials are imposed on all O-H bonds (denoted by the VrH scheme) to prevent proton hopping and thus may not be applicable for systems involving spontaneous proton hopping. In this work, we introduce an improved restraining scheme with a repulsive potential Vrep to compute the surface acidities of systems in which proton hopping is spontaneous and fast. In this Vrep scheme, a Buckingham-type repulsive potential Vrep is applied between the deprotonation site and all other protons in DFTMD simulations. We first verify the Vrep scheme by calculating the pKa values of H2O and aqueous HS- solution (i.e., strong conjugate bases) and then apply it to the SnO2(110)/H2O interface. It is found that the Vrep scheme leads to a prediction of the point of zero charge (PZC) of 4.6, which agrees well with experiment. The intrinsic individual pKa values of the terminal five-coordinated Sn site (Sn5cOH2) and bridge oxygen site (Sn2ObrH+) are 4.4 and 4.7, respectively, both being almost the same as the PZC. The similarity of the two pKa values indicates that dissociation of terminal water has almost zero free energy at this proton hopping interface (i.e., partial water dissociation), as expected from the acid-base equilibrium on SnO2.
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Anodic electrodeposition of ligand-free iridium oxide on titanium with high mass loading and study of electrochemical treatments. J Electroanal Chem (Lausanne) 2020. [DOI: 10.1016/j.jelechem.2020.113831] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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11
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Beyond thermodynamic-based material-screening concepts: Kinetic scaling relations exemplified by the chlorine evolution reaction over transition-metal oxides. Electrochim Acta 2020. [DOI: 10.1016/j.electacta.2019.135555] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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12
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A Study on the Catalytic Activity and Service Lifetime of RuO 2‐TiO 2Composite Electrode with TNTs as Interlayer. ChemistrySelect 2019. [DOI: 10.1002/slct.201902750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Coupling of Surface Chemistry and Electric Double Layer at TiO 2 Electrochemical Interfaces. J Phys Chem Lett 2019; 10:3871-3876. [PMID: 31241948 DOI: 10.1021/acs.jpclett.9b01355] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Surfaces of metal oxides at working conditions are usually electrified because of the acid-base chemistry. The charged interface compensated with counterions forms the so-called electric double layer. The coupling of surface chemistry and the electric double layer is considered to be crucial but is poorly understood because of the lack of information at the atomistic scale. Here, we used the latest development in density functional theory-based finite-field molecular dynamics simulation to investigate the pH dependence of the Helmholtz capacitance at electrified rutile TiO2(110)-NaCl electrolyte interfaces. It is found that, because of competing forces from surface adsorption and from the electric double layer, water molecules have a stronger structural fluctuation at high pH, and this leads to a much larger capacitance. It is also seen that interfacial proton transfers at low pH increase significantly the capacitance value. These findings elucidate the microscopic origin of the same trend observed in titration experiments.
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Colloidal synthesis of high-performance FeSe/CoSe nanocomposites for electrochemical oxygen evolution reaction. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2018.11.191] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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15
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Communication: Computing the Helmholtz capacitance of charged insulator-electrolyte interfaces from the supercell polarization. J Chem Phys 2018; 149:031103. [DOI: 10.1063/1.5038639] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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16
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Facile crosslinking of poly(vinylpyrrolidone) by electro-oxidation with IrO2-based anode under potentiostatic conditions. J APPL ELECTROCHEM 2018. [DOI: 10.1007/s10800-018-1237-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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17
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Electrifying model catalysts for understanding electrocatalytic reactions in liquid electrolytes. NATURE MATERIALS 2018; 17:592-598. [PMID: 29867166 DOI: 10.1038/s41563-018-0088-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Accepted: 04/24/2018] [Indexed: 06/08/2023]
Abstract
Electrocatalysis is at the heart of our future transition to a renewable energy system. Most energy storage and conversion technologies for renewables rely on electrocatalytic processes and, with increasing availability of cheap electrical energy from renewables, chemical production will witness electrification in the near future1-3. However, our fundamental understanding of electrocatalysis lags behind the field of classical heterogeneous catalysis that has been the dominating chemical technology for a long time. Here, we describe a new strategy to advance fundamental studies on electrocatalytic materials. We propose to 'electrify' complex oxide-based model catalysts made by surface science methods to explore electrocatalytic reactions in liquid electrolytes. We demonstrate the feasibility of this concept by transferring an atomically defined platinum/cobalt oxide model catalyst into the electrochemical environment while preserving its atomic surface structure. Using this approach, we explore particle size effects and identify hitherto unknown metal-support interactions that stabilize oxidized platinum at the nanoparticle interface. The metal-support interactions open a new synergistic reaction pathway that involves both metallic and oxidized platinum. Our results illustrate the potential of the concept, which makes available a systematic approach to build atomically defined model electrodes for fundamental electrocatalytic studies.
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Atomically-defined model catalysts in ultrahigh vacuum and in liquid electrolytes: particle size-dependent CO adsorption on Pt nanoparticles on ordered Co3O4(111) films. Phys Chem Chem Phys 2018; 20:23702-23716. [DOI: 10.1039/c8cp03770a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have studied particle size effects on atomically-defined model catalysts both in ultrahigh vacuum (UHV) and under electrochemical (EC) conditions in liquid electrolytes.
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Is an electric field always a promoter of wetting? Electro-dewetting of metals by electrolytes probed by in situ X-ray nanotomography. Faraday Discuss 2017; 199:101-114. [DOI: 10.1039/c6fd00239k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We developed a special electrochemical cell enabling quantitative analysis and in situ X-ray nanotomography of metal/electrolyte interfaces subject to corrosion. Using this cell and applying the nodoid model to describe menisci formed on tungsten wires during anodization, the evolution of the electrolyte surface tension, the concentration of reaction products, and the meniscus contact angle were studied. In contrast to the electrowetting effect, where the applied electric field decreases the contact angle of electrolytes, anodization of the tungsten wires increases the contact angle of the meniscus. Hence, an electric field favors dewetting rather than wetting of the newly formed surface. The discovered effect opens up new opportunities for the control of wetting phenomena and calls for the revision of existing theories of electrowetting.
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Isoelectric points and points of zero charge of metal (hydr)oxides: 50years after Parks' review. Adv Colloid Interface Sci 2016; 238:1-61. [PMID: 27890403 DOI: 10.1016/j.cis.2016.10.005] [Citation(s) in RCA: 178] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 10/27/2016] [Accepted: 10/28/2016] [Indexed: 02/06/2023]
Abstract
The pH-dependent surface charging of metal (hydr)oxides is reviewed on the occasion of the 50th anniversary of the publication by G.A. Parks: "Isoelectric points of solid oxides, solid hydroxides, and aqueous hydroxo complex systems" in Chemical Reviews. The point of zero charge (PZC) and isoelectric point (IEP) became standard parameters to characterize metal oxides in aqueous dispersions, and they define adsorption (surface excess) of ions, stability against coagulation, rheological properties of dispersions, etc. They are commonly used in many branches of science including mineral processing, soil science, materials science, geochemistry, environmental engineering, and corrosion science. Parks established standard procedures and experimental conditions which are required to obtain reliable and reproducible values of PZC and IEP. The field is very active, and the number of related papers exceeds 300 a year, and the standards established by Parks remain still valid. Relevant experimental techniques improved over the years, especially the measurements of electrophoretic mobility became easier and more reliable, are the numerical values of PZC and IEP compiled by Parks were confirmed by contemporary publications with a few exceptions. The present paper is an up-to-date compilation of the values of PZC and IEP of metal oxides. Unlike in former reviews by the same author, which were more comprehensive, only limited number of selected results are presented and discussed here. On top of the results obtained by means of classical methods (titration and electrokinetic methods), new methods and correlations found over the recent 50years are presented.
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Kinetic study of the hydrogen evolution reaction in slightly alkaline electrolyte on mild steel, goethite and lepidocrocite. J Electroanal Chem (Lausanne) 2016. [DOI: 10.1016/j.jelechem.2016.11.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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22
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Electrogeneration of Active Chlorine in a Filter-Press-Type Reactor Using a New Sb2O5 Doped Ti/RuO2-ZrO2 Electrode: Indirect Indigoid Dye Oxidation. INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING 2016. [DOI: 10.1515/ijcre-2016-0095] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
This paper presents the study on active chlorine mediated electrochemical oxidation of model solutions that simulate textile effluents containing an indigoid dye (indigo carmine) and sodium chloride (0.05 M) using a new Sb2O5-doped Ti/RuO2-ZrO2 electrode. The study was carried out in a filter-press electrochemical reactor specially designed to minimize flow deviations and provide homogeneous mass transfer flux over the electrode surface. Firstly, the mass-transfer-limited chloride oxidation reaction was studied in the absence of dye in order to understand the active chlorine formation process. Changes in pH, chloride concentration and UV-visible absorption spectra during electrolysis reveal the formation of active chlorine (mainly hypochlorite) with current efficiencies for chloride oxidation of 0.558 and 0.503 at 10 and 20 mA cm−2, respectively. Secondly, chloride oxidation was investigated in the presence of indigo carmine dye (0.5 mM) where in-situ generated active chlorine was responsible for -C=C- bond breaking and dye degradation. The solution discoloration followed a pseudo-first order kinetics where kinetic coefficient was inversely proportional to dye concentration. The oxidation with active chlorine had an average efficiency of 0.7 and a very competitive energy consumption between 49.2 and 128.5 kW h (kg COD removed)−1 depending on current density and flow rate.
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23
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Controllable Deposition of Platinum Layers on Oxide Surfaces for the Synthesis of Fuel Cell Catalysts. ChemElectroChem 2016. [DOI: 10.1002/celc.201600255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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24
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Titanium coated with high-performance nanocrystalline ruthenium oxide synthesized by the microwave-assisted sol–gel procedure. J Solid State Electrochem 2016. [DOI: 10.1007/s10008-016-3343-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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25
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Crosslinking of poly(vinylpyrrolidone) activated by electrogenerated hydroxyl radicals: A first step towards a simple and cheap synthetic route of nanogel vectors. Electrochem commun 2016. [DOI: 10.1016/j.elecom.2015.12.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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The surface sulfur doping induced enhanced performance of cobalt catalysts in oxygen evolution reactions. Chem Commun (Camb) 2016; 52:9450-3. [DOI: 10.1039/c6cc04387a] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Surface sulfur-doping can change the electronic properties of Co catalysts, leading to significantly improved performance in oxygen evolution reactions.
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Revised Oxygen Evolution Reaction Activity Trends for First-Row Transition-Metal (Oxy)hydroxides in Alkaline Media. J Phys Chem Lett 2015; 6:3737-42. [PMID: 26722749 DOI: 10.1021/acs.jpclett.5b01650] [Citation(s) in RCA: 172] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
First-row transition-metal oxides and (oxy)hydroxides catalyze the oxygen evolution reaction (OER) in alkaline media. Understanding the intrinsic catalytic activity provides insight into improved catalyst design. Experimental and computationally predicted activity trends, however, have varied substantially. Here we describe a new OER activity trend for nominally oxyhydroxide thin films of Ni(Fe)O(x)H(y) > Co(Fe)O(x)H(y) > FeO(x)H(y)-AuO(x) > FeO(x)H(y) > CoO(x)H(y) > NiO(x)H(y) > MnO(x)H(y). This intrinsic trend has been previously obscured by electrolyte impurities, potential-dependent electrical conductivity, and difficulty in correcting for surface-area or mass-loading differences. A quartz-crystal microbalance was used to monitor mass in situ and X-ray photoelectron spectroscopy to measure composition and impurity levels. These new results provide a basis for comparison to theory and help guide the design of improved catalyst systems.
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Photoelectrochemical Treatment of α,β-Unsaturated Ketones on TiO2-RuO2/Ti Electrode. Electrocatalysis (N Y) 2015. [DOI: 10.1007/s12678-015-0278-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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29
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Synergistic enhancement of the electro-oxidation of methanol at tailor-designed nanoparticle-based CoOx/MnOx/Pt ternary catalysts. Electrochim Acta 2015. [DOI: 10.1016/j.electacta.2015.02.231] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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30
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Cobalt-iron (oxy)hydroxide oxygen evolution electrocatalysts: the role of structure and composition on activity, stability, and mechanism. J Am Chem Soc 2015; 137:3638-48. [PMID: 25700234 DOI: 10.1021/jacs.5b00281] [Citation(s) in RCA: 770] [Impact Index Per Article: 85.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Cobalt oxides and (oxy)hydroxides have been widely studied as electrocatalysts for the oxygen evolution reaction (OER). For related Ni-based materials, the addition of Fe dramatically enhances OER activity. The role of Fe in Co-based materials is not well-documented. We show that the intrinsic OER activity of Co(1-x)Fe(x)(OOH) is ∼100-fold higher for x ≈ 0.6-0.7 than for x = 0 on a per-metal turnover frequency basis. Fe-free CoOOH absorbs Fe from electrolyte impurities if the electrolyte is not rigorously purified. Fe incorporation and increased activity correlate with an anodic shift in the nominally Co(2+/3+) redox wave, indicating strong electronic interactions between the two elements and likely substitutional doping of Fe for Co. In situ electrical measurements show that Co(1-x)Fe(x)(OOH) is conductive under OER conditions (∼0.7-4 mS cm(-1) at ∼300 mV overpotential), but that FeOOH is an insulator with measurable conductivity (2.2 × 10(-2) mS cm(-1)) only at high overpotentials >400 mV. The apparent OER activity of FeOOH is thus limited by low conductivity. Microbalance measurements show that films with x ≥ 0.54 (i.e., Fe-rich) dissolve in 1 M KOH electrolyte under OER conditions. For x < 0.54, the films appear chemically stable, but the OER activity decreases by 16-62% over 2 h, likely due to conversion into denser, oxide-like phases. We thus hypothesize that Fe is the most-active site in the catalyst, while CoOOH primarily provides a conductive, high-surface area, chemically stabilizing host. These results are important as Fe-containing Co- and Ni-(oxy)hydroxides are the fastest OER catalysts known.
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Charge-storage process in IrO 2 -SnO 2 mixed-oxide electrodes. Role of coating composition, solution pH and Temperature. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.10.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Influence of the nature of the electrode material and process variables on the kinetics of the chlorine evolution reaction. The case of IrO2-based electrocatalysts. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.07.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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33
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The electric double layer at a rutile TiO₂ water interface modelled using density functional theory based molecular dynamics simulation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:244108. [PMID: 24861088 DOI: 10.1088/0953-8984/26/24/244108] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A fully atomistic model of a compact electric double layer at the rutile TiO2(1 1 0)-water interface is constructed by adding protons to bridging oxygens or removing them from H2O molecules adsorbed on terminal metal cation sites. The surface charge is compensated by F(-) or Na(+) counter ions in outer as well as inner sphere coordination. For each of the protonation states the energy of the TiO2 conduction band minimum is determined relative to the standard hydrogen electrode by computing the free energy for the combined insertion of an electron in the solid and a proton in solution away from the double layer using density functional theory based molecular dynamics methods. Interpreted as electrode potentials, this gives an estimate of the capacitance which is compared to the capacitance obtained from the difference in the average electrostatic potentials in the solid and aqueous phase. When aligned at the point of zero charge these two methods lead to almost identical potential-charge profiles. We find that inner sphere complexes have a slightly larger capacitance (0.4 F m(-2)) compared to outer sphere complexes (0.3 F m(-2)).
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Iridium As Catalyst and Cocatalyst for Oxygen Evolution/Reduction in Acidic Polymer Electrolyte Membrane Electrolyzers and Fuel Cells. ACS Catal 2014. [DOI: 10.1021/cs4011875] [Citation(s) in RCA: 415] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Oxygen Electrochemistry as a Cornerstone for Sustainable Energy Conversion. Angew Chem Int Ed Engl 2013; 53:102-21. [DOI: 10.1002/anie.201306588] [Citation(s) in RCA: 1039] [Impact Index Per Article: 94.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Indexed: 11/09/2022]
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Die Elektrochemie des Sauerstoffs als Meilenstein für eine nachhaltige Energieumwandlung. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201306588] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Electrochemically deposited ZnO films: an XPS study on the evolution of their surface hydroxide and defect composition upon thermal annealing. J Solid State Electrochem 2013. [DOI: 10.1007/s10008-013-2281-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Atomic scale insights into electrochemical versus gas phase oxidation of HCl over RuO2-based catalysts: A comparative review. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2012.12.099] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Particle Formation during Oxidation Catalysis with Cp* Iridium Complexes. J Am Chem Soc 2012; 134:9785-95. [DOI: 10.1021/ja3033026] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Electrochemical behaviors of co-deposited Pb/Pb–MnO2 composite anode in sulfuric acid solution – Tafel and EIS investigations. J Electroanal Chem (Lausanne) 2012. [DOI: 10.1016/j.jelechem.2012.02.011] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Surface Chemistry of Ruthenium Dioxide in Heterogeneous Catalysis and Electrocatalysis: From Fundamental to Applied Research. Chem Rev 2012; 112:3356-426. [DOI: 10.1021/cr200247n] [Citation(s) in RCA: 509] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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42
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Alignment of electronic energy levels at electrochemical interfaces. Phys Chem Chem Phys 2012; 14:11245-67. [DOI: 10.1039/c2cp41652b] [Citation(s) in RCA: 194] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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The electrocatalytic properties of an IrO2/SnO2 catalyst using SnO2 as a support and an assisting reagent for the oxygen evolution reaction. Electrochim Acta 2012. [DOI: 10.1016/j.electacta.2011.10.044] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Comparison of morphology, stability and electrocatalytic properties of Ru0.3Ti0.7O2 and Ru0.3Ti0.4Ir0.3O2 coated titanium anodes. RUSS J ELECTROCHEM+ 2011. [DOI: 10.1134/s1023193511110061] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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High specific surface area Ce0.8Zr0.2O2 promoted Pt/C electro-catalysts for hydrogen oxidation and CO oxidation reaction in PEMFCs. Electrochim Acta 2011. [DOI: 10.1016/j.electacta.2011.06.076] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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46
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Effect of praseodymium oxide and cerium–praseodymium mixed oxide in the Pt electrocatalyst performance for the oxygen reduction reaction in PAFCs. J APPL ELECTROCHEM 2011. [DOI: 10.1007/s10800-011-0310-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Interfacial electron transfer dynamics following laser flash photolysis of [Ru(bpy)2((4,4'-PO3H2)2bpy)]2+ in TiO2 nanoparticle films in aqueous environments. CHEMSUSCHEM 2011; 4:216-227. [PMID: 21328552 DOI: 10.1002/cssc.201000356] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Nanosecond laser flash photolysis has been used to investigate injection and back electron transfer from the complex [(Ru(bpy)(2)(4,4'-(PO(3)H(2))(2)bpy)](2+) surface-bound to TiO(2) (TiO(2)-Ru(II)). The measurements were conducted under conditions appropriate for water oxidation catalysis by known single-site water oxidation catalysts. Systematic variations in average lifetimes for back electron transfer, <τ(bet)>, were observed with changes in pH, surface coverage, incident excitation intensity, and applied bias. The results were qualitatively consistent with a model involving rate-limiting thermal activation of injected electrons from trap sites to the conduction band or shallow trap sites followed by site-to-site hopping and interfacial electron transfer, TiO(2)(e(-))-Ru(3+) → TiO(2)-Ru(2+). The appearance of pH-dependent decreases in the efficiency of formation of TiO(2)-Ru(3+) and in incident-photon-to-current efficiencies with the added reductive scavenger hydroquinone point to pH-dependent back electron transfer processes on both the sub-nanosecond and millisecond-microsecond time scales, which could be significant in limiting long-term storage of multiple redox equivalents.
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Arsenic(III) Remediation from Contaminated Water by Oxidation and Fe/Al Co-Precipitation. ACTA ACUST UNITED AC 2011. [DOI: 10.4236/jwarp.2011.39075] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Effects of surfactants and pH of medium on zeta potential and aggregation stability of titanium dioxide suspensions. COLLOID JOURNAL 2010. [DOI: 10.1134/s1061933x10040125] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Effect of anodic prepolarization on hydrogen entry into iron at cathodic potentials in 0.1M NaOH without and with EDTA or sodium molybdate. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2010.03.084] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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