Boosting highly active defect MoV sites for amorphous molybdenum sulfide from catalyst-substrate effect toward efficient hydrogen evolution

Simultaneously achieving abundant active sites and high intrinsic activity is a major challenge to developing highly efficient MoSx-based materials for hydrogen evolution reaction (HER) since there might be a contradictory relationship between loading amounts and intrinsic activity of amorphous molybdenum sulfide (MoSx). Herein, we have for the first time demonstrated a strategy for the electrochemical oxidation of carbon cloth (CC) fol-lowed by mild acidification employing (NH4)2MoS4 as the precursor to boost highly active defect MoV sites (DMSs) for MoSx toward efficient HER. In our strategy, a high potential at the anode results in a high concen-tration of O-containing groups on the surface of CC, which favors loading [Mo3S13]2-clusters or MoSx on CC (MoSx/CC) for achieving abundant DMSs. Impressively, such oxidation does not disrupt the sp2 hybridized carbon of the substrate. Hence, the excellent conductivity of CC guarantees high intrinsic activity of the as-synthesized MoSx/CC samples. On the other hand, excessively high potential stimulates excessive growth and accumulation of [Mo3S13]2-clusters for further increasing loading amounts of MoSx. Nevertheless, such loading is at the expense of DMSs, indicating a great decrease in the quantity of active sites. Furthermore, excessive oxidation leads to unsatisfactory conductivity of CC, owing to breaking the sp2-conjugated system of CC. At the same time, the theoretical prediction and experimental investigation reveal that the intrinsic activity of DMSs will significantly decrease at excessively high potential. By regulating electrochemical potential to 1.8 V, a balance between the loading amounts of MoSx and intrinsic activity of MoSx/CC is achieved to boost highly active DMSs for efficient HER. Consequently, the optimal MoSx/CC exhibit the most excellent HER activity among all counterparts, accompanied by reliable stability. This work presents a new strategy for realizing abundant active sites with high intrinsic activity for MoSx-based materials toward efficient HER from the catalyst-substrate effect.