FeCo bimetallic phosphides heterostructure for hydrogen production via sulfion oxidation assisted alkaline seawater splitting

Abstract

Developing energy-efficient strategies for hydrogen evolution reaction (HER) from alkaline seawater is highly desirable yet remains challenging owing to sluggish oxygen evolution reaction (OER) and competing side reactions. Therefore, a rationally designed nanoporous iron-cobalt bimetallic phosphide (np-Fe5Co-P) electrocatalyst with dual functionality for HER and sulfion oxidation reaction (SOR) was synthesized. To achieve 50 mA cm-2, the required voltages of the np-Fe5Co-P electrode were -0.211 V and 0.311 V vs. reversible hydrogen electrode (vs. RHE), respectively. The synergistic contribution of the interconnected nanoporous ligament network as well as enriched FeP/Co2P heterointerfaces, underlies exceptional electrocatalytic activity of np-Fe5Co-P. When np-Fe5Co-P was utilized as both the anode as well as cathode, the SOR-assisted coupling alkaline seawater splitting system exhibited an ultralow overall cell potential of 0.636 V at 50 mA cm-2 and stable operation for 300 h (50 mA cm-2 and 0.717 V), representing a reduction of 1.181 V relative to that of traditional alkaline seawater electrolysis, while simultaneously achieving selective oxidation and recovery of sulfides. This work provides a promising route for low-energy hydrogen generation integrated with value-added sulfur conversion in complex alkaline seawater environments.