Graphene oxide variations in NiGraf during OER: structural dynamics of nickel-based electrocatalysts for enhanced water electrolysis

Alkaline water electrolysis, which relies on efficient and durable electrocatalysts made from earth-abundant metals like nickel for both hydrogen and oxygen evolution reactions, is a crucial energy storage technology for the transition to renewable energy. In operando techniques enabling the observation of active catalysts under relevant working conditions by monitoring the surface oxidation state and local atomic-structure transformation, can probe the active sites and promote fundamental understanding of the reaction mechanisms. In this study we present a new operando investigation of the electrocatalyst NiGraf by synchrotron X-ray Powder Diffraction and Pair Distribution Function. The structural changes in the crystal phases of this new metal organic alloy comprised of graphene oxide entrapped in nickel-based jamborite nanoparticles during voltammetry cycles in the OER range revealed a first reversible variation in the distance between GO planes during the reaction, and the subsequent reaching of the irreversible activation stage of the electrocatalyst. The technique, which couples Pair Distribution Function, Principal Component Analysis and operando electrochemistry is a new tool for the study of electrocatalysts in action.