Synergistically enhanced activity and stability of bifunctional nickel phosphide/sulfide heterointerface electrodes for direct alkaline seawater electrolysis

Abstract

Direct electrolysis of seawater to generate hydrogen is an attractive but challenging renewable energy storage technology. Reasonable design of seawater electrolysis catalysts should integrate high activity for hydrogen evolution reaction (HER)/ oxygen evolution reaction (OER) and enhanced physical/electrochemical stability in seawater. Herein, we demonstrate the development of a Ni foam (NF) supported interfacial heterogeneous nickel phosphide/sulfide (Ni2P/NiS2) microsphere electrocatalyst (NiPS/NF) through a facile electrodeposition and subsequent phosphorization/sulfuration process. After NiS2 modification, a charge redistribution on the heterointerface is demonstrated and a more advantageous covalent nature of the Ni-P bond is obtained for more easily adsorption of H* and H2O. The NiPS/NF thus yields an impressive electrocatalytic performance in 1.0 M KOH, requiring small overpotentials of 169 and 320 mV for HER and OER to obtain a high current density of 100 mA cm−2, respectively. The NiPS/NF can also work efficiently in alkaline seawater with negligible activity degradation, requiring overpotentials of only 188 and 344 mV for a current density of 100 mA cm−2 for HER and OER, respectively. A synergistically enhanced physical/electrochemical long-term stability NiPS/NF in saline water is also demonstrated.