Spin-induced electron transfer simultaneously enhancing intrinsic activity and stability of amorphous MoS_x-based materials toward efficient hydrogen evolution

Designing MoS_x-based materials to simultaneously realize high intrinsic activity and reliable stability remains quite challenging since there is a contradictory relationship between them. For example, high intrinsic activity or efficient charge transfer indicates that the MoS_x-based materials can provide abundant electron-rich sulfur atoms for the hydrogen evolution reaction (HER); a lot of H⁺ will attack these sulfur atoms; thus, this results in the massive missing of sulfur atoms and poor electrochemical stability. Instead, electron-deficient sulfur atoms lead to an unsatisfactory HER activity regardless of high stability. Herein, a feasible strategy for spin-state regulation is proposed to promote charge transfer, strengthen the Mo-S bond and activate sulfur atoms of MoS_x toward efficient HER. In our strategy, the spin transition of the Co-doped species increases the unpaired electrons, favors wide spin channels and accelerates localized electron transfer; additionally, Co-doping decreases the band-gap of the electrocatalyst. These factors collectively improve charge transfer during the HER. Second, the spin- and electronegativity-induced electron redistribution decreases the Mo-S bond length, which efficiently inhibits the massive missing of bridging or apical sulfur atoms. Third, introducing Co species into [Mo₃S₁₃]²⁻ nanoclusters activates the terminal sulfur atoms owing to reasonable charge accumulation to favor the absorption of H*. With these benefits, the optimized electrocatalyst demonstrates high intrinsic activity and reliable stability. Our work provides a feasible strategy to design and synthesize the outstanding MoS_x-based materials from the spin effect and presents an insightful understanding of the possible mechanism about hydrogen spillover as well as enhancing their durability and structural stability toward efficient electrocatalysis.