Bimetallic Phosphide Heterostructure Coupled with Ultrathin Carbon Layer Boosting Overall Alkaline Water and Seawater Splitting

Seawater electrolysis is promising for green hydrogen production but hindered by the sluggish reaction kinetics of both cathode and anode, as well as the detrimental chlorine chemistry environment. Herein, a self-supported bimetallic phosphide heterostructure electrode strongly coupled with an ultrathin carbon layer on Fe foam (C@CoP-FeP/FF) is constructed. When used as an electrode for the hydrogen and oxygen evolution reactions (HER/OER) in simulated seawater, the C@CoP-FeP/FF electrode shows overpotentials of 192 mV and 297 mV at 100 mA cm⁻², respectively. Moreover, the C@CoP-FeP/FF electrode enables the overall simulated seawater splitting at the cell voltage of 1.73 V to achieve 100 mA cm⁻², and operate stably during 100 h. The superior overall water and seawater splitting properties can be ascribed to the integrated architecture of CoP-FeP heterostructure, strongly coupled carbon protective layer, and self-supported porous current collector. The unique composites can not only provide enriched active sites, ensure prominent intrinsic activity, but also accelerate the electron transfer and mass diffusion. This work confirms the feasibility of an integration strategy for the manufacturing of a promising bifunctional electrode for water and seawater splitting.