Hierarchical FeCo LDH/NiSe heterostructure electrocatalysts with rich heterointerfaces for robust water splitting at an industrial-level current density

Abstract

Sustainable hydrogen production by electrocatalytic water splitting is a promising energy storage technology yet challenging due to the sluggish kinetics of the oxygen evolution reaction (OER). Rationally designed robust and high-efficiency non-noble metal electrocatalysts for large-current-density OER are highly desirable for industrial-grade hydrogen production. Herein, a unique hierarchical heterostructure electrocatalyst composed of FeCo layered double hydroxide nanosheets and a NiSe nanowire array grown on Ni foam (FeCo LDH/NiSe@NF) is demonstrated. The optimized FeCo LDH/NiSe@NF exhibits an excellent OER activity with low overpotentials of 230, 266 and 298 mV at current densities of 100, 500 and 1000 mA cm⁻² in an alkaline solution. In particular, it can deliver 1000 mA cm⁻² without much decay after the long-term stability test for 100 h. Both the experimental results and theoretical calculations reveal that reasonable construction of a hierarchical heterostructure, as well as the strong interaction at the heterointerface between NiSe and FeCo LDH can not only offer sufficient exposure of the surface active sites, better electrochemical conductivity and structural stability, but also effectively optimize electronic configurations and lower the reaction energy barriers, consequently facilitating the reaction kinetics especially in large-current-density alkaline water electrolysis. Moreover, a two-electrode electrolyzer using FeCo LDH/NiSe@NF and NiCoP/NiCoS_x@NF as the anode and cathode only needs a cell voltage of 1.849 V to reach 1000 mA cm⁻² in 30 wt% KOH solution at 80 °C. The high catalytic activity and long-term stability of the catalyst at large current densities have exceeded most electrocatalysts reported, highlighting its great potential in large-scale applications.