Ni3S2/Cu–NiCo LDH heterostructure nanosheet arrays on Ni foam for electrocatalytic overall water splitting

Abstract

The development of highly efficient transition metal-based catalysts for overall water splitting is of extreme significance for promoting large-scale sustainable utilization of hydrogen energy and energy conversion. Herein, we report novel 3D Ni₃S₂/Cu–NiCo LDH heterostructure nanosheet arrays grown on nickel foam as a promising bifunctional electrocatalyst for the OER and HER. In this design, copper ions are firstly doped into NiCo LDH to tune the electronic structure and enhance the inherent activity of pristine LDH. Metallic Ni₃S₂ is then introduced to establish a coupling heterostructure interface with Cu–NiCo LDH to boost the conductivity and activity. The incorporation of Cu ions and Ni₃S₂ into NiCo LDH also creates more active sites through crystal structure disorder and interface defects. Moreover, the 3D hierarchical nanosheet arrays can accelerate the electrolyte diffusion, promote the rapid release of gas bubbles, and ensure fast electron/mass transport along with strong electrochemical stability. All these merits endow the materials with a superior overall water splitting ability in an alkaline environment, showing low overpotentials of 119 and 218 mV for the OER and overpotentials of 156 and 304 mV for the HER at 10 and 100 mA cm⁻², respectively. Furthermore, the overall water electrolytic cell using Ni₃S₂/Cu–NiCo LDH as both electrodes can reach 100 mA cm⁻² at 1.75 V with outstanding durability. This study provides a new strategy and insights for the exploration of high activity non-noble metal catalysts for overall water splitting.