Molybdenum sulfide cocatalyst activation upon photodeposition of cobalt for improved photocatalytic hydrogen production activity of ZnCdS

Molybdenum sulfide (MoSx) is a prevalent photocatalytic and electrocatalytic material, attributed to its highly active unsaturated sites. Despite that, its intrinsic activity is still under expectation for large-scale hydrogen evolution reaction (HER). Though the incorporation of Co-promotor could further promote MoSx activity, a tedious preparation is required due to the incompatible properties of Co and Mo. Herein, we report a facile one-step precipitation of cobalt-modified amorphous molybdenum sulfide (Co-MoSx) cocatalyst while focusing on its promotional effects to ZnCdS at λ > 420 nm region. Co-MoSx at different Co/Mo ratios were photochemically-anchored on ZnCdS support through an in-situ light-induced reduction at ambient conditions. In particular, ZnCdS/Co-MoSx (Co/Mo = 1/4, 1 mol%) was emerged as the best formulated photocatalyst, with HER rate and apparent quantum efficiency (AQE) of 551.48 μmol h−1 and 21.7% (420 nm), respectively. While reducing the overpotential for HER, Co-modification could also facilitate the separation of photogenerated electrons and holes for the enhanced HER. Therefore, the reported HER rate of ZnCdS/Co-MoSx is in superior to that of ZnCdS/MoSx and pristine ZnCdS, by 1.4 times and 23 times, respectively. Meanwhile, similar ascendency of Co-MoSx was also observed in its comparison against the benchmarked Pt, Au and Ag co-catalysts. Additionally, the recycling test evinced the satisfactory stability of ZnCdS/Co-MoSx catalyst, with a slightly reduced activity observed after 25 h consecutive HER, marking an average STH of 1.4% under AM 1.5G solar simulator. This work provides a facile way to synthesis Co-modified MoSx co-catalyst that rendered with excellent properties for efficient HER.