Self-supported hierarchical CuOx@Co3O4 heterostructures as efficient bifunctional electrocatalysts for water splitting

Abstract

The preparation of low-cost and efficient bifunctional catalysts towards water splitting is essential for the production of clean H₂ energy. Herein, a hierarchical Co₃O₄-decorated CuO–Cu₂O nanorod core–shell structure was in situ grown on a Cu foam (denoted as CuO_x@Co₃O₄ NRs/CF) and investigated as a bifunctional catalyst for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline solution. Benefiting from its large electrochemical surface area and the synergetic effects between the CuO_x core and Co₃O₄ shell, CuO_x@Co₃O₄ NRs/CF exhibited considerable catalytic activity, which resulted in a small overpotential of 240 mV for the OER and 242 mV for the HER at a current density of 50 mA cm⁻², along with low Tafel slopes of 46 and 61 mV dec⁻¹, respectively. Remarkably, CuO_x@Co₃O₄ NRs/CF could continuously produce O₂ or H₂ for at least 24 h with negligible decline in catalytic activity, and it gave rise to high faradaic efficiencies of 99.7% and 96.4% for the OER and HER, respectively. The electrochemical performance of CuO_x@Co₃O₄ NRs/CF was dramatically improved as compared to those of its CuO_x NRs/CF counterpart and also most reported Cu-based water splitting electrocatalysts.