Spin-Dominated Reconstruction Kinetics in Prussian Blue Analog Enables Efficient Seawater Splitting

The spin state of metal centers is identified as a pivotal descriptor dominating the electrochemical reconstruction kinetics of Prussian blue analogs (PBAs). We demonstrate that constructing an interfacial electric field in MnFeO_x/PBA pre-catalyst triggers a partial high spin configuration of Fe centers, introducing partial t_2g occupancy and thereby substantially enhancing metal to ligand π backdonation. This electronic perturbation destabilizes the cyanide ligand field, rendering the entire coordination framework susceptible to rapid electrochemically driven transformation into active (oxy)hydroxide phases under OER conditions. The reconstructed catalyst (R-MnFeO_x/PBA) exhibits markedly accelerated reconstruction kinetics and delivers ultralow overpotential of 201 mV to reach 10 mA cm^‒2 in simulated seawater. Crucially, R-MnFeO_x/PBA enabled alkaline membrane electrode assemblies (MEAs) affords Faraday efficiencies of up to 97.6% and can operate stably for 1150 h at 1000 mA cm^‒2. This work establishes spin-state engineering as a unique pre-catalyst design strategy that bridges electronic structure manipulation with reconstruction-enhanced electrocatalysis.