LAUSR

Si is regarded as a promising photocathode material for solar hydrogen evolution reaction (HER) because of its small band gap and highly negative conduction band edge. However, bare Si electrodes have high overpotential because of sluggish HER kinetics on the Si surface. In this study, molybdenum tungsten sulfide (MoS2-WS2) was decorated on Si photocathode as the co-catalyst to accelerate HER kinetics. The catalytic performance of MoS2-WS2 was further enhanced by introducing phosphate materials. Phosphate-modified molybdenum tungsten sulfide (PO-MoWS) was deposited on Si photoabsorbers to provide the optimal current of -15.0 mA cm-2 at 0 V (vs. reversible hydrogen electrode). Joint characterizations of X-ray photoelectron and X-ray absorption spectroscopies demonstrated that the phosphate materials dominantly coordinated with the WS2 components of the PO-MoWS catalysts. Moreover, these phosphate materials induced a large number of sulfur vacancies in the PO-MoWS/Si electrodes that contributed to achieving the ideal catalytic activity. Herein, TiO2 thin film was prepared as the protective layer to improve the stability of the photocathodes. The PO-MoWS/2 nm TiO2/Si electrode maintained 83.8% of the initial photocurrent after chronoamperometric measurement was performed for 8000 s.