A highly efficient and durable water splitting system: platinum sub-nanocluster functionalized nickel–iron layered double hydroxide as the cathode and hierarchical nickel–iron selenide as the anode

Abstract

Developing cost-efficient and effective catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains a great challenge for application in high-efficiency water electrolyzers. In this work, we design a highly efficient and durable water splitting system in an alkaline solution, in which platinum (Pt) sub-nanocluster (average size: 0.59 nm) functionalized nickel–iron layered double hydroxide nanosheets on carbon fiber cloth (Pt–NiFe LDH/CC) serve as the cathode and hierarchical (Ni_0.77Fe_0.23)Se₂ nanosheets on CC ((Ni_0.77Fe_0.23)Se₂/CC) act as the anode. For the HER, the three-dimensional (3D) Pt–NiFe LDH/CC electrode with an ultralow Pt content (1.56 wt%) drives a current density of 10 mA cm⁻² at an ultralow overpotential of 28 mV. For the OER, the edge-rich (Ni_0.77Fe_0.23)Se₂/CC electrode displays a current density of 10 mA cm⁻² at a small overpotential of 228 mV, and the Tafel slope is as low as 69 mV dec⁻¹. More importantly, the assembled Pt–NiFe LDH/CC||(Ni_0.77Fe_0.23)Se₂/CC water splitting electrolyzer exhibits a high current density of 30 mA cm⁻² at a low cell voltage of 1.57 V, which is superior to that of the electrolyzer assembled using commercial 20 wt% Pt/C and RuO₂ electrodes (30 mA cm⁻² at 1.62 V). Additionally, the Pt–NiFe LDH/CC||(Ni_0.77Fe_0.23)Se₂/CC electrolyzer displays excellent stability over 40 h even at a high current density of 50 mA cm⁻², which shows its great potential in the practical applications of full water splitting.