Interfacial electron bridge-mediated Fe and Co dual-site electrocatalysts for alkaline seawater splitting

Abstract

To address the sluggish reaction kinetics in seawater electrolysis, this study developed a novel one-dimensional CoP/FeP dual-site catalyst by integrating electrospinning and vapor-phase phosphidation. By precisely controlling the phosphidation temperature, the Kirkendall effect was utilized to construct hierarchical mesoporous heterointerfaces with engineered 30 nm interfacial gaps of core–shell nanostructures, thereby yielding a CoFeP composite with a high specific surface area of 29.09 m² g⁻¹. The as-prepared catalyst exhibited exceptional bifunctional performance in an alkaline seawater electrolyte, achieving ultralow overpotentials of 145 mV for the HER and 240 mV for the OER at 10 mA cm⁻², along with a low overall seawater electrolysis voltage of 1.57 V. Notably, it exhibited outstanding corrosion resistance, maintaining stable operation for 240 hours at 100 mA cm⁻² with only 5.53% voltage decay, further confirming its excellent resistance to chloride-induced corrosion. Synchrotron radiation and in situ characterization studies revealed that the cross-interfacial electron coupling engineering promoted the formation of Fe–P–Co electron-bridging bonds and directional Co to Fe charge transfer, thereby improving the charge transport efficiency. During the OER, dynamic surface reconstruction generated active Co/FeOOH species with Fe–O–Co electron-bridging bonds, as confirmed by the detection of the critical *OOH intermediate via in situ infrared spectroscopy. Density functional theory calculations further verified that the *OH to *O energy barrier was reduced to 0.505 eV by the reconstructed phase. This study introduces a novel interface-engineering strategy for developing highly active and stable electrocatalysts for sustainable seawater splitting.