In situ hydrothermal growth of metallic Co9S8-Ni3S2 nanoarrays on nickel foam as bifunctional electrocatalysts for hydrogen and oxygen evolution reactions

Conductivity and morphology are the two important factors affecting the performance of electrocatalysts . In this article, a facile two-step hydrothermal process was developed to grow Co 9 S 8 -Ni 3 S 2 nanoarrays on nickel foam (Co 9 S 8 -Ni 3 S 2 NAs/NF). The as-obtained catalyst possessed a novel morphology, in which the Co 9 S 8 nanoneedles were surrounded by Ni 3 S 2 ultrathin nanosheets . The resultant Co 9 S 8 -Ni 3 S 2 nanoarrays not only permitted more exposures of active sites but also facilitated the charges and ions transport along the nanoarrays. Moreover, both Co 9 S 8 and Ni 3 S 2 exhibited metallic properties allowed the catalysts with conductivity (metallic conductor vs. semiconductor). Co 9 S 8 -Ni 3 S 2 NAs/NF exhibited excellent electrocatalytic activities for both HER and OER in 1.0 M KOH solution. To reach a large current density of 100 mA cm −2 , it only required overpotentials of 204 mV and 346 mV for HER and OER, respectively. After long-term electrolysis, the high activities were still preserved. This work indicates efficient electrocatalysts can be obtained by the rational design of the heterostructure , which sheds some light on the development of noble metal-free electrocatalysts.