A bifunctional and stable Ni–Co–S/Ni–Co–P bistratal electrocatalyst for 10.8%-efficient overall solar water splitting

Abstract

Stable and cost-effective catalysts with low kinetic overpotentials for both the anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER) are indispensable for the large-scale implementation of electrochemical water splitting. In this study, we developed an efficient, stable and bifunctional Ni–Co–S/Ni–Co–P bistratal electrocatalyst on Ni foam (NF) using simple electrodeposition methods. The efficient contact at the Ni–Co–P/NF interface along with the porous Ni–Co–S surface results in the superior electrocatalytic activity of the bistratal layer in a basic solution for both the OER and HER. Only −0.11 V vs. RHE is required at a current density of −20 mA cm⁻² for the HER and 1.47 V vs. RHE at 50 mA cm⁻² for the OER, significantly outperforming bare Ni–Co–S or Ni–Co–P on NF. Most crucially, when functioning as a bifunctional catalyst for overall water splitting, a small cell potential of 1.49 V can drive 10 mA cm⁻² which can be sustained for more than two days. Subsequently, 10.8%-efficient overall solar water splitting was achieved when driven by three ordinary Si solar cells. Such a bistratal structure is expected to provide a new platform for the design of highly efficient, low-cost and durable catalysts for water electrolysis systems.