Self-assembly of NiFe-LDH@Ni3S2 sub-nanosheets catalyst for overall water splitting

Abstract

The development of water splitting catalysts for generating high-purity hydrogen in large-scale is still facing challenges in terms of improving efficiency and stability. Herein, Ni3S2-coated NiFe layered double hydroxides sub-nanosheets with a hierarchical heterostructure (NiFe-LDH@Ni3S2) were prepared on nickel foam (NF) by a strategy of continuous hydrothermal synthesis. The introduction of S2− broke the hydrogen bonds between NiFe-LDH layers and separated into sub-nanosheets with a thickness of only about 1 nm, which enlarged the active areas of NiFe-LDH@Ni3S2/NF by a factor of 5.7. The coexisting charge channels Ni-O-Ni and Ni-S-Ni in the material enhanced the electrochemical activity, resulting in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) overpotentials as low as 179 mV and 116 mV at 10 mA cm−2 in 1.0 M KOH. Moreover, after a 50-hour chronopotentiometry test at 50 mA cm−2, the overpotential for OER and HER decreased only 0.013 V and 0.059 V, respectively. Furthermore, under the conditions of simulating industrial hydrogen production with an electrolyte of 6.0 M KOH and a temperature of 75 °C, after a 140-hour test for durability, the current density decreased only 0.75% at the cell voltage of 1.70 V.