Schottky switch derived by metallic W5N4 | catalyst junction: Switch-on to enhance catalytic activity and durability in water splitting reaction

Abstract

In water splitting reactions, (oxy)hydroxide catalysts generated in situ have been commonly suggested as real-time active species; however, their poor electrical conductance severely restricts catalytic reactivity. We here demonstrate that a classical unipolar Schottky junction electrode can nullify non-conductive lamination of poor-conductive catalysts; we use a water splitting reaction in our model study. Nickel-tungsten nitride (Ni-W5N4) alloy catalyzed HER, recording 10 mA/cm2 at overpotential of 11 mV (without iR compensation). The Ni-W5N4|NiFeOOH forms a rectifying Schottky junction to accelerate electron-flow across the junction; this results in excellent OER activity. The forward biased Ni-W5N4|NiFeOOH Schottky junction yielded 10 mA/cm2 at overpotential of 181 mV (without iR compensation). The remarkable catalytic activity is attributed to the fundamental Schottky junction rather than to electrode|electrolyte interface. Moreover, demonstration of overall seawater splitting using a full cell setup showed high current density of 100 mA/cm2 at only 230 mV overpotential with outstanding durability.