Understanding Competitive Electrochemical Reactions on Strained Surfaces

In heterogeneous electrocatalysis, reactants adsorb on a materials surface, and subsequently transfer electrons to or from the solid in conjunction with ionic motion, forming and breaking chemical bonds. This complex interface—between a solid surface and a reactive gas and/or liquid—can change dramatically with the electrochemical potential that drives such reactions. For example, materials can change oxidation state (where changes in the surface oxidation state are associated with adsorbates, and bulk changes require diffusion of oxygen through the material itself) or change their structure/phase. Such changes in a catalyst are intimately linked to their functionality and activity for desired electrochemical reactions.<br/><br/>We have been investigating how metal electrocatalysts react with species from aqueous solution by electrochemical approaches with complementary spectroscopy. We are particularly motivated by complex reaction environments where multiple species – such as reducible reactants and protons – compete for sites on the surface, influencing the activity for reduction reactions. This competition and resultant activity depends on the applied voltage, but also characteristics of the electrocatalyst itself, such as strain and the presence of defects. We will share how such changes in a material’s bulk influence competitive processes on the surface and the formation of hydride phases under electrochemical conditions.