pH-Universal Water Splitting Catalyst: Ru-Ni Nanosheet Assemblies

Although electrochemical water splitting is an effective and green approach to produce oxygen and hydrogen, the realization of efficient bifunctional catalysts that are stable in variable electrolytes is still a significant challenge. Herein, we report a three-dimensional hierarchical assembly structure composed of an ultrathin Ru shell and a Ru-Ni alloy core as a catalyst functioning under universal pH conditions. Compared with the typical Ir/C-Pt/C system, superior catalytic performances and excellent durability of the overall water splitting under universal pH have been demonstrated. The introduction of Ni downshifts the d-band center of the Ru-Ni electrocatalysts, modulating the surface electronic environment. Density functional theory results reveal that the mutually restrictive d-band interaction lowers the binding of (Ru, Ni) and (H, O) for easier O-O and H-H formation. The structure-induced eg-dz2 misalignment leads to minimization of surface Coulomb repulsion to achieve a barrier-free water-splitting process.