Efficient and Stable Silicon Photocathodes Coated with Vertically Standing Nano-MoS₂ Films for Solar Hydrogen Production

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 2 catalyst with ∼2 nm Al 2 O 3 protected n + p-Si. Al 2 O 3 acts as a protective and passivative layer of the Si surface, while the sputtering method using a MoS 2 target along with a postannealing leads to a vertically standing, conformal, and crystalline nano-MoS 2 layer on Al 2 O 3 /n + p-Si photocathode. Efficient (0.4 V vs RHE onset potential and 35.6 mA/cm 2 saturated photocurrent measured under 100 mA/cm 2 Xe lamp illumination) and stable (above 120 h continuous water splitting) photocathode was obtained, which opens the door for the MoS 2 catalyst to be applied in photoelectrochemical hydrogen evolution in a facile and scalable way.