Influence of Divalent Transition-Metal Cations on the Oxygen Evolution Reaction Activity of Layered Double Hydroxide Nanosheets in Seawater Electrolysis

Developing cost-effective, durable electrocatalysts for seawater electrolysis requires precise regulation of intermediate adsorption energetics governed by the d-band center (<i>E</i>_d) of active metal sites. Here, we systematically decouple the intrinsic oxygen evolution reaction (OER) activity of monotransition-metal hydroxides (MAl-LDHs, M = Fe, Co, Ni) by synthesizing phase-pure catalysts to eliminate synergistic effects. Electrochemical evaluations in alkaline simulated seawater reveal CoAl-LDH's supremacy, achieving overpotentials of 340 mV @ 10 mA cm^-2, which is lower than FeAl- and NiAl-LDH, alongside rapid kinetics (Tafel slope: 62.42 mV dec^-1) and exceptional stability (50 mA cm^-2, 50 h in natural seawater). Density functional theory (DFT) calculations rationalize this performance hierarchy through a Sabatier-type volcano relationship that CoAl-LDH's optimized d-band center, closest to the theoretical optimum, balances intermediate adsorption-desorption dynamics, minimizing the rate-determining step energy barrier. This <i>E</i>_d-mediated activity trend, corroborated by Gibbs free energy analysis, establishes a universal design principle for seawater OER catalysts that precise electronic structure engineering of 3d transition metals to optimize intermediate binding. Our work not only identifies cobalt as the optimal catalytic center but also provides a transferable strategy for advancing energy conversion technologies through orbital-level modulation.