Highly Efficient and Stable Overall Water Splitting Electrocatalyst α-Co(OH)2@PN/NF with Hierarchical and Mesoporous Structure

Abstract

Exploiting efficient, stable, and cost-effective bifunctional water splitting catalysts is extremely challenging. Here, we developed three-dimensional hierarchical porous catalysts with heterogeneous interfaces, α-Co(OH)2@PN/NF, by a facile two-step electrodeposition approach. This bifunctional electrocatalyst exhibits excellent hydrogen and oxygen evolution performance as well as stability in alkaline aqueous environments. In 1 M KOH solution, small overpotential of 187 mV was needed to drive the hydrogen evolution reaction (HER) at 100 mA cm−2, while the overpotential for the oxygen evolution reaction (OER) was 324 mV at 100 mA cm−2 current density. In addition, the two-electrode electrolytic cell with α-Co(OH)2@PN/NF electrodes for HER and OER required only approximately 1.74 V at 100 mA cm−2 with over 75 h of stable operation. According to the physical-chemical characterization results and electrochemical tests, such excellent performance was attributed to the synergistic effect of the heterogeneous interface and the hierarchical porous structure between α-Co(OH)2 and the nickel oxide layer, as it facilitates the transfer of electrons and the diffusion of ions.