Local Proton‐Rich Solid Solution Catalyst with a Cluster‐in‐Cluster Structure for Anti‐interference Seawater Splitting

The poor proton coverage of electrocatalysts in neutral hydrogen evolution reaction (HER) and the incapacity to resist alkali hydroxides for seawater electrolysis have resulted in a large kinetics gap from acidic water splitting. Facing this challenge, a cluster-in-cluster solid solution catalyst with a proton-rich microenvironment and anti-interference interface composed of an amorphous hafnium oxide cluster penetrating in crystalline iridium cluster (HfOx-in-Ir SSC), is reported which can achieve superior activity for direct seawater splitting. The structure characterizations, in situ FT-IR and Raman, and theoretical calculations reveal that the HfOx clusters in the Ir cluster endow an interfacial proton-rich microenvironment by increasing the coverage and optimizing the adsorption of *H, thereby achieving a low overpotential of 30 mV in neutral electrolytes. Fascinating, the interfaces of HfOx-in-Ir SSC catalysts present abundant *H and OH* species and simultaneously superior anti-poison to Cl⁻/ClO⁻ and anti-deposition to Mg(OH)₂, eventually achieving an ultra-low overpotential of 117 mV at 10 mA cm⁻² and excellent stability in seawater splitting.