Water splitting in a photoelectrochemical cell, which converts sunlight into hydrogen energy, has recently received intense research. Silicon is suitable as a viable light-harvesting material for constructing such cell; however, there is a need to improve its stability and explore a cheap and efficient cocatalyst. Here we fabricate highly efficient and stable photocathodes by integrating crystalline MoS catalyst with ∼2 nm AlO protected np-Si. AlO acts as a protective and passivative layer of the Si surface, while the sputtering method using a MoS target along with a postannealing leads to a vertically standing, conformal, and crystalline nano-MoS layer on AlO/np-Si photocathode. Efficient (0.4 V vs RHE onset potential and 35.6 mA/cm saturated photocurrent measured under 100 mA/cm Xe lamp illumination) and stable (above 120 h continuous water splitting) photocathode was obtained, which opens the door for the MoS catalyst to be applied in photoelectrochemical hydrogen evolution in a facile and scalable way.

A combination of hydrogen passivation, electroless deposition of a Pt catalyst and coating a TiO protective layer leads to an unprecedented 11.5% energy conversion efficiency and one-week stability of an nnp-Si photocathode for solar water splitting.

Many earth-abundant transition metal dichalcogenides (TMDs) have been employed as catalysts for H2 evolution reaction (HER); however, their impactful integration onto photocathodes for photoelectrochemical (PEC) HER is less developed. In this study, we directly sputtered a MoSe2 catalyst onto an n+p-Si photocathode for efficient and stable PEC-HER. An onset potential of 0.4 V vs. RHE, a saturated photocurrent of 29.3 mA/cm2, a fill factor of 0.32, and an energy conversion efficiency of 3.8% were obtained under 100 mA/cm2 Xe lamp illumination. Such superior PEC properties were ascribed to the nearly vertically standing two dimensional MoSe2 rough surface layer and the sharp interface between Si and MoSe2 with small charge transfer resistance. The balance between the reflectivity of the electrode surface and the absorptivity of MoSe2 was also discussed. In addition, the MoSe2 layer can protect the n+p-Si photocathode with a 120 h stability due to its initial growth on Si with high flatness and compactness. This study provides a path to the effective and scalable growth of TMDs onto the Si photocathode aiming for high efficiency and stability.

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