Interfacial solvation pre-organizes the transition state of the oxygen evolution reaction

Abstract

The sluggish kinetics of the oxygen evolution reaction are an energetic bottleneck for green hydrogen production via water electrolysis. The reaction proceeds over a surface that undergoes (frustrated) phase transitions to accommodate bias-dependent excess charge. Here we perform Arrhenius analysis of common catalysts and correlate the activation energy and pre-exponential factor with the oxide's structural adaptation via operando X-ray absorption spectroscopy and high-energy X-ray diffraction. We observe that the kinetics switch from a regime that is probably dominated by interfacial solvation to one where the surface energetics take over. This happens right at a transition potential between the α or β phases into the γ-crystal structure of Ni (oxy)hydroxides and when spectroscopic fingerprints of key intermediates emerge. Importantly, this turning potential is independent of the loading or the surface area and informs on the intrinsic catalyst activity. These results suggest that the catalyst activity is intrinsically linked to the initial interfacial solvation (pre-)step.