Controlled synthesis of Co9S8@NiCo2O4 nanorod arrays as binder-free electrodes for water splitting with impressive performance

Abstract The hydrogen and oxygen generation has been regarded as the most promising solution through electrochemical water splitting for the sake of alleviating the energy crisis and climate change. In this paper, we developed an in-situ deposition approach for depositing NiCo2O4 on the surface of Co9S8, and then the loading amount of NiCo2O4 was controlled by regulating the deposited number of cycles. In addition, the materials were used as catalysts for oxygen production and hydrogen production for the first time. When Co9S8@NiCo2O4-10 cycles, Co9S8@NiCo2O4-70 cycles and Co9S8 is used as a bifunctional catalyst, Co9S8@NiCo2O4-70 cycles // Co9S8@NiCo2O4-10 cycles displays a smaller cell voltage (1.55 V@10 mA cm−2) than Co9S8 (1.68 V@10 mA cm−2). Density functional theory calculation is used to calculate the water adsorption energy on the surface of the material to further reveal the reaction mechanism of water oxidation process. The work provides a new idea for the development of a relatively low toxicity and environmental friendly bifunctional electrocatalyst for industrial water electrolysis applications.