Understanding the Role of Strain on Electrochemical Reaction Kinetics: Oxygen Evolution on Mechanically Strained Rutile TiO2 As a Model System
Authors: Carvalho O. Quinn , Miller-Link Elisa , Greenaway Ann L 
Published: August 2024

Electrocatalysis offers a green alternative (when coupled with renewably-sourced electrons) to conventional carbon-intensive chemical fuel and commodity production processes. Electrochemical device efficiency, however, is limited by the sluggish kinetics of multi-electron transfer reactions, such as the oxygen evolution reaction (OER). Theoretical adsorption free energy scaling relationships predict large oxygen evolution overpotentials (>370 mV) for metal oxides performing the adsorbate evolution mechanism, a series of four proton-concerted electron transfer steps.1 Identifying catalyst design strategies that overcome or “break” scaling relations (i.e. strain,2 high entropy alloys,3 non-concerted proton and electron transfer mechanisms4,5) would provide a means to lower kinetic potential energy penalties and enhance the efficiency and economic incentives for further development of renewably-driven electrochemical reactions.
Here we investigate the role of mechanically induced strain on the OER activity of polycrystalline rutile TiO2 thin films, grown on the super elastic alloy nitinol (NiTi) and mechanically strained by tensile tester. Our work characterizes how strain manifests in these complex polycrystalline systems with complementary physical characterization techniques (e.g. X-ray diffraction and Raman spectroscopy) and relates strain to OER performance in alkaline electrolytes. We contextualize our results within the framework of conventional adsorption scaling relationships to hypothesize how tensile strain influences reaction intermediate adsorption affinities, inferring implications for the OER kinetics of benchmark IrO2 and RuO2 catalysts that share the same crystal structure as the rutile TiO2 considered here.
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