Study of the Mechanism of Photoactivated Hydrogen Evolution on a Silicon Photocathode with a-MoSx Thin-Film Catalyst

Silicon cathodes for the efficient production of hydrogen in the photoelectrochemical process of water splitting have been created and studied. A photoactive layer on p-Si wafer was obtained by pulsed laser doping of the wafer with phosphorus from a solution of orthophosphoric acid. A film of amorphous molybdenum sulfide (a-MoSx) up to 4 nm thick was deposited on the surface of the modified n(+)p-Si wafer. This caused a significant increase in photocurrents in the acid solution as compared to the bare n(+)p-Si. The composition of the catalytic film was modified during the photoelectrochemical process of hydrogen evolution. The study of the energy bands at the interface of the a-MoSx heterojunction with the n(+)-Si layer showed that the reaction of hydrogen evolution proceeded, probably, because of electron tunneling through the a-MoSx film. Using the density functional theory, a thermodynamic analysis of the possible effect of chemical changes on the silicon surface and in the a-MoSx film itself on the efficiency of hydrogen catalysis was carried out.