Triggering water splitting to hydrogen and oxygen by phase chemistry in nanoscale nickel elctrocatalysts

Abstract

The rational design of highly efficient catalysts for the hydrogen evolution reaction (HER) in alkaline solutions is of great significance for water splitting. In this work, we deliberately devise a series of steps to obtain nickel oxide nanosheets on carbon nanotubes (NiO/CNT) for the oxygen evolution reaction (OER) and nickel oxide and nickel disulfide heterogeneous structures on CNTs (NiS2/NiO/CNT) for HER in alkaline conditions, respectively. The NiO/CNT sample shows an efficient OER activity in 1.0 M KOH and requires an overpotential of 310 mV to achieve a current density of 10 mA cm−2. The NiS2/NiO/CNT sample with a heterogeneous structure drives a current density of 10 mA cm−2 at an overpotential of 93 mV in the 1.0 M KOH, presenting a significantly enhanced HER activity compared with that of the pure NiO and NiS2 phases. The potential of 1.62 V allows achieving a current density of 10 mA cm−2 for overall water splitting with the NiS2/NiO/CNT and NiO/CNT catalysts as the cathode and anode, respectively.