Metallic Co9S8 nanosheets grown on carbon cloth as efficient binder-free electrocatalysts for the hydrogen evolution reaction in neutral media.

The development of efficient non-noble metal hydrogen-evolving electrocatalysts is of paramount importance for sustainable hydrogen production from water. Herein, we report the direct growth of metallic Co₉S₈ nanosheets on carbon cloth (CC) through a facile one-pot solvothermal method. We also show that the introduction of a tiny amount of Zn²⁺ ions (Zn : Co mol ratio of 0.5–1 : 100) in the synthesis system can reduce the thickness, improve the crystallinity, and optimize the surface structure of Co₉S₈ nanosheets, without Zn-doping. Furthermore, we show that the resulting Co₉S₈/CC materials can serve as efficient, binder-free, non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) under neutral conditions (pH 7). In particular, the Co₉S₈/CC material (synthesized in the presence of Zn²⁺ ions) affords a current density of 10 mA cm⁻² at a low overpotential of 175 mV, has great catalytic stability as long as 100 h, and gives about 100% faradaic yield towards the HER in neutral media. The material's excellent catalytic performance toward the HER is attributed primarily to the synergistic effects of Co₉S₈'s intrinsic catalytic ability, the ultrathin nanosheet array architecture and the self-supporting feature. [ABSTRACT FROM AUTHOR]