Special atmosphere annealed Co3O4 bifunctional catalysts with oxygen defects for high-efficient water splitting

Electrochemical water splitting is widely recognized as an economical and sustainable method for producing high-purity hydrogen using renewable energy sources. Herein, we prepared 3D urchin-like sphere structures of Co3O4 to serve as an excellent bifunctional catalyst for overall water splitting. Different Co3O4 samples were directly synthesized on Ni foam through hydrothermal and annealing processes under various atmospheric conditions, leading to the formation of oxygen vacancies with varying concentrations. Specifically, the Co3O4/NF-Ar/O2 demonstrates outstanding catalytic performance for both OER (η20 = 269 mV) and HER (η10 = 135 mV), while maintaining excellent durability in 1 M KOH. Electrolysis cells employing Co3O4/NF-Ar/O2 as both anode and cathode demonstrate a low cell voltage of 1.56 V to achieve 10 mV cm−2 in alkaline conditions. The excellent catalytic performance can be mainly attributed to the urchin-like nanostructure and the appropriate concentration of oxygen vacancies. This research provides further insights into the application of the method to induce oxygen vacancies in low-cost and high-efficiency transition metal oxides (TMOs)-based catalysts for electrochemical reaction.