Efficient Photoelectrochemical Hydrogen Evolution of Amorphous Group VI Metal Chalcogenides on Si Micropyramids

Hydrogen, a clean, storable, and high-energy density energy carrier, is a promising sustainable alternative for meeting the global energy demand and achieving an environmentally friendly fuel economy. Utilizing an integrated photoelectrochemical (PEC) system to directly convert solar to hydrogen via water splitting is one of the most promising approaches. Platinum and other noble metals remain the best catalysts for solar-driven hydrogen evolution reaction (HER), but the high cost and scarcity greatly limit their large scale deployment. In this work, we synthesized efficient yet low-cost HER electrocatalysts, amorphous MoS_xCl_y and MoSe_xCl_y, via a facial chemical vapor deposition (CVD) method, and discovered when these catalysts were coupled with light absorber planar p-Si could make efficient and robust photocathodes for solar-driven HER. Moreover, by utilizing a special designed n⁺p Si micropyramid structure, we were able to further improve the photocurrent density, onset voltage, as well as the overall power conversion efficiency. This superior performance is originated from the significant improvement in light harvesting properties from Si nanostructuring as well as the optimized interface between the catalysts and Si substrate via the direct CVD growth. Outstanding stability was also demonstrated over long-term operation, suggesting these heterostructures are promising earth-abundant alternatives to photocathodes based on noble metal catalysts for solar-driven hydrogen production.