Electrocatalysis

Katsaounis, Alexandros; Brosda, S.; Vayenas, C.G.

doi:10.1002/9783527610426.bard050002

Encyclopedia of Electrochemistry 2007

DOI: 10.1002/9783527610426.bard050002

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Electrocatalysis

Alexandros Katsaounis

S. Brosda

C.G. Vayenas

Abstract: The sections in this article are Introduction Adsorption Basic Electrokinetic Principles and Experimental Techniques Electrokinetic and Mass‐transport Control The Measurement of IR ‐free Electrocatalyst Overpotential Cyclic Voltammetry … Show more

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Cited by 3 publications

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“…The tip shield method allows one to determine the activity of individual spots for the OER when neighboring spots in the array also generate oxygen. The OER is one of the most studied reactions in electrocatalysis since it is involved in many electrochemical industrial processes (cathodic protection, water electrolysis, metal recovery, photoelectrochemical water oxidation) and its kinetics limits the entire electrolysis process, since is considerably slower than most cathodic processes. – If the reaction is conducted in acidic media, the list of anode materials is restricted to IrO 2 and RuO 2 because of their high activity and chemical resistance under the operating conditions . RuO 2 shows the higher activity, but IrO 2 lasts about 20 times longer and thus is more interesting from an industrial point of view …”

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confidence: 99%

Screening of Oxygen Evolution Electrocatalysts by Scanning Electrochemical Microscopy Using a Shielded Tip Approach

et al. 2008

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Oxygen evolution electrocatalysts in acidic media were studied by scanning electrochemical microscopy (SECM) in the substrate generation-tip collection (SG-TC) imaging mode with a 100 microm diam tip. Pure IrO2 and Sn(1-x)Ir(x)O2 combinatorial mixtures were prepared by a sol-gel route to form arrays of electrocatalyst spots. The experimental setup has been developed to optimize screening of electrocatalyst libraries under conditions where the entire array is capable of the oxygen evolution reaction (OER). The activity of individual spots was determined by reducing the interference from the reaction products of neighboring spots diffusing to the tip over the spot of interest. A gold layer deposited on the external wall of the SECM tip was used as a tip shield. In this study the shield was kept at a constant potential to reduce oxygen under mass transfer controlled conditions. The tip shield consumes oxygen coming from the neighbor spots in the array and enables the tip to correctly detect the activity of the spot below the tip. Simulations and experimental results are shown, demonstrating the effectiveness of the tip shield with the SG-TC setup in determining the properties of the composite materials and imaging arrays.

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Screening of Oxygen Evolution Electrocatalysts by Scanning Electrochemical Microscopy Using a Shielded Tip Approach

et al. 2008

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Green Synthesis and Modification of RuO2 Materials for the Oxygen Evolution Reaction

2020

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Ion exchange method as a green synthesis route is proposed to prepare hydrous ruthenium oxide nanoparticles (H-RuO 2). Calcination of H-RuO 2 at 350°C resulted in the crystalline rutile RuO 2 nanoparticles (C-RuO 2). Treatment of H-RuO 2 with 20 vol% ammonium hydroxide solution under microwave irradiation and calcination at 350°C resulted in a highly electrocatalytic active crystalline RuO 2 nanoparticles (A-C-RuO 2). Electrocatalytic performances of H-RuO 2 , C-RuO 2 and A-C-RuO 2 for the oxygen evolution reaction in 0.50 mol L −1 H 2 SO 4 medium are evaluated and compared. Improved performances towards the oxygen evolution reaction are observed for A-C-RuO 2 when compared to C-RuO 2. Based on XRD, TEM, XPS and Raman characterizations performed on all the specimens, it is deduced that the physicochemical properties (crystallinity, mean crystallite size, level of hydrous rutile content) are varied for A-C-RuO 2 when compared to C-RuO 2. Structure-property correlation has been established to describe the higher electrocatalytic activity of A-C-RuO 2 .

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The Role of Redox Potential and Molecular Structure of Co(II)-Polypyridine Complexes on the Molecular Catalysis of CO2 Reduction

et al. 2021

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In this work, we report the electrochemical response of a family of Co(II) complexes, [CoII(L)3]2+ and [CoII(L’)2]2+ (L = 2,2’-bipyridine, 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline; L’ = terpyridine and 4-chloro-terpyridine), in the presence and absence of CO2 in order to understand the role of the redox potential and molecular structure on the molecular catalysis of CO2 reduction. The tris chelate complexes exhibited three electron transfer processes [CoII(L)3]2+ ⇄ [CoIII(L)3]3+ + 1e−, [CoΙΙ(L)3]2++1e− ⇄ [CoΙ(L)3]+, and [CoΙ(L)3]+ + 2e- ⇄ [CoΙ(L)(L−)2]−. In the case of complexes with 1,10-phen and 2,2-bipy, the third redox process showed a coupled chemical reaction [CoΙ(L)(L−)2]− → [CoΙ(L−)2]− + L. For bis chelate complexes, three electron transfer processes associated with the redox couples [CoΙΙ(L)2]/[CoIII(L)2]3+, [CoΙΙ(L)2]2+/[CoΙ(L)2]+, and [CoΙ(L)2]+/[CoΙ(L)(L−)] were registered, including a coupled chemical reaction only for the complex containing the ligand 4-chloro-terpyridine. Foot to the wave analysis (FOWA) obtained from cyclic voltammetry experiments allowed us to calculate the catalytic rate constant (k) for the molecular catalysis of CO2 reduction. The complex [Co(3,4,7,8-tm-1,10-phen)3]2+ presented a high k value; moreover, the complex [Co(4-Cl-terpy)3]2+ did not show catalytic activity, indicating that the more negative redox potential and the absence of the coupled chemical reaction increased the molecular catalysis. Density functional theory (DFT) calculations for compounds and CO2 were obtained to rationalize the effect of electronic structure on the catalytic rate constant (k) of CO2 reduction.

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Electrocatalysis

Abstract: The sections in this article are Introduction Adsorption Basic Electrokinetic Principles and Experimental Techniques Electrokinetic and Mass‐transport Control The Measurement of IR ‐free Electrocatalyst Overpotential Cyclic Voltammetry … Show more

Cited by 3 publications

References 141 publications

Screening of Oxygen Evolution Electrocatalysts by Scanning Electrochemical Microscopy Using a Shielded Tip Approach

Screening of Oxygen Evolution Electrocatalysts by Scanning Electrochemical Microscopy Using a Shielded Tip Approach

Green Synthesis and Modification of RuO2 Materials for the Oxygen Evolution Reaction

The Role of Redox Potential and Molecular Structure of Co(II)-Polypyridine Complexes on the Molecular Catalysis of CO2 Reduction

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