The urchin-like sphere arrays Co3O4 as a bifunctional catalyst for hydrogen evolution reaction and oxygen evolution reaction

Electrochemical water splitting has attracted great interest because of the growing demand for sustainable energy and increasing concerns for the environment. We present a facile strategy to design the three-dimensional (3D) urchin-like sphere arrays Co 3 O 4 as an effective bifunctional catalyst for electrochemical water splitting. The 3D urchin-like Co 3 O 4 was directly grown on Ni foam by a hydrothermal reaction and annealing treatment at a low temperature. This process offers several advantages including facile synthesis, binder-free, and low cost. The 3D urchin-like Co 3 O 4 as a catalyst for hydrogen evolution reaction exhibits a low onset potential (−130 mV vs. RHE) and good cycling stability in an alkaline electrolyte . When urchin-like Co 3 O 4 is used as a catalyst for oxygen evolution reaction , the onset potential is at 1.46 V (vs. RHE) with a low overpotential of only 230 mV. The good catalytic activity can be attributed to the unique urchin-like nanostructure , abundant mesopores, and low charge-transfer resistance (compared with Co 3 O 4 NPs). In addition, H 2 and O 2 generation was performed using Co 3 O 4 as both cathode and anode catalysts with a potential of 1.64 V to reach a current density of 10 mA cm −2 .