Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion
KAUST DepartmentCatalysis for Energy Conversion (CatEC)
Chemical Science Program
KAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division
Online Publication Date2015-09-08
Print Publication Date2015-11
Permanent link to this recordhttp://hdl.handle.net/10754/578916
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AbstractMicrokinetic analyses of aqueous electrochemistry involving gaseous H2 or O2, i.e., hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are revisited. The Tafel slopes used to evaluate the rate determining steps generally assume extreme coverage of the adsorbed species (θ ≈ 0 or ≈1), although, in practice, the slopes are coverage-dependent. We conducted detailed kinetic analyses describing the coverage-dependent Tafel slopes for the aforementioned reactions. Our careful analyses provide a general benchmark for experimentally observed Tafel slopes that can be assigned to specific rate determining steps. The Tafel analysis is a powerful tool for discussing the rate determining steps involved in electrocatalysis, but our study also demonstrated that overly simplified assumptions led to an inaccurate description of the surface electrocatalysis. Additionally, in many studies, Tafel analyses have been performed in conjunction with the Butler-Volmer equation, where its applicability regarding only electron transfer kinetics is often overlooked. Based on the derived kinetic description of the HER/HOR as an example, the limitation of Butler-Volmer expression in electrocatalysis is also discussed in this report.
CitationInsight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion 2015, 5:13801 Scientific Reports
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