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

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 (Ni0.77Fe0.23)Se-2 nanosheets on CC ((Ni0.77Fe0.23)Se-2/CC) act as the anode. For the HER, the threedimensional (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 (Ni0.77Fe0.23) Se-2/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 parallel to(Ni0.77Fe0.23) Se-2/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 parallel to(Ni0.77Fe0.23) Se-2/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.