Unlocking the potential of MoS₂ for efficient hydrogen generation by controlling hydrothermal conditions

Introducing foreign elements, clusters, and nanoparticles to two-dimensional MoS₂ is the usual approach to getting highly active electrocatalysts for the hydrogen evolution reaction (HER) without or with a minimum amount of precious metals. Yet, the catalytic properties of bare MoS₂ can still optimize the final performance of electrocatalysts. In the present work, it is unraveled how the structure of MoS₂ can be systematically changed by hydrothermal reaction parameters (temperature: 180–240 °C; volume: 40–80 %), resulting in varying shape, crystallinity, stacking form, phase, oxidation state, and HER activity. The reaction temperature and volume control can finely tune the 1T/2H phase ratio and conversion yield from Mo⁶⁺ to Mo⁴⁺, which affect HER efficiency. This brings the optimized synthesis of MoS₂ on carbon cloth at 200 °C with 60 % reaction volume, showing the best HER overpotential of −189 mV at 10 mA cm⁻² current density. Using this condition, finally, rhenium-doped and platinum nanoparticle-deposited MoS₂ composites showed overpotentials of −140 mV and −12 mV, respectively, to further improve performance. Our study contributes to the hydrothermal synthesis of two-dimensional materials for HER applications and lays the groundwork for non-precious metal-based sustainable energy catalyst development.