Mechanoelectrochemical Catalysis of the Effect of Elastic Strain on a Platinum Nanofilm for the ORR Exerted by a Shape Memory Alloy Substrate

Abstract

Both the ligand effect and surface strain can affect the electrocatalytic reactivity. In that matter exists a need to be fundamentally understood; however, there is no effective strategy to isolate the strain effect in electrocatalytic systems. In this research we show how the elastic strain in a platinum nanofilm varies the catalytic activity for the oxygen reduction reaction, a key barrier to the wide applications of fuel cells. NiTi shape memory alloy was selected as the substrate to strain engineer the deposited Pt nanofilm in both compressively and tensilely strained states by taking advantage of the two-way shape memory effect for the first time. We demonstrate that compressive strain weakens the Pt surface adsorption and hence improves the ORR activity, which reflects in a 52% enhancement of the kinetic rate constant and a 27 mV positive shift of the half-wave potential for the compressively strained 5 nm Pt compared to the pristine Pt. Tensile strain has the opposite effect, which is in general agreement with the proposed d-band theory.