Phosphate-Triggered Interlayer Engineering in Cobalt-Iron Silicate Hydroxides Enables Efficient and Durable Oxygen Evolution Reaction

Efficient oxygen evolution catalysis is pivotal to advancing water electrolysis as a scalable route to green hydrogen. For layered transition-metal hydroxide catalysts, incorporating hetero-anions is widely employed to boost oxygen evolution reaction (OER) activity, yet the underlying promotion mechanism remains debated. Here, we use cobalt-iron silicate hydroxides (CFSH) as a flexible and robust layered platform to systematically interrogate anion effects by introducing SO₄²⁻ and PO₄³⁻. Notably, phosphate incorporation induces pronounced structural variations and simultaneously optimizing the electronic structure, thereby markedly accelerating OER kinetics. The phosphate-modified CFSH delivers a low overpotential of 258 mV at 10 mA cm⁻² and retains 98.5% of its activity after 24 h of continuous electrolysis. Density functional theory (DFT) further attributes the performance enhancement to an upshifted Co 3d band center and a balanced adsorption energetics, as reflected by a moderate ΔG_O*-ΔG_HO*. This work establishes a mechanistically informed paradigm for leveraging targeted anion regulation in layered architectures to achieve high-performance OER electrocatalysis.