Efficient Hydrogen Evolution Catalysts Based on Hierarchical Flowerlike Ni_xCo_9–xS₈ Nanosheets

Abstract

In terms of the need for a low-carbon economy and alleviating the need for energy security, hydrogen (H2) plays a key role in promoting a sustainable economy because it is clean and efficient. The bottleneck of the hydrogen evolution reaction (HER) can be overcome by developing high-efficiency electrocatalysts. Using a simple solvothermal method, p-NixCo9–xS8 with polyvinylpyrrolidone (PVP) compounds are successfully prepared with synergistic effects between bimetallic sulfides. The resulting p-NixCo9–xS8 catalyst shows a hierarchical flowerlike nanosheet shape based on physical representations. An ultrathin and porous nanosheet surface facilitates rapid electrolyte injection and provides abundant active sites for H+ adsorption, thus giving p-NixCo9–xS8 nanosheets outstanding HER performance. Furthermore, the synergistic effect of a bimetallic electrocatalyst is helpful to improve HER activity. In comparison to NixCo9–xS8 nanosheets without PVP, individual Co9S8 particles, and individual Ni9S8 nanosheets, p-NixCo9–xS8 nanosheets have a lower overpotential (137 mV to 10 mA cm–2), Tafel slope (109 mV dec–1), and 95.7% retention of current after 1000 cycles in the HER process.