Amorphous Phosphorus-Doped Cobalt Sulfide Modified on Silicon Pyramids for Efficient Solar Water Reduction

Cobalt sulfide (CoSx) functioned as a co-catalyst to accelerate the kinetics of photogenerated electrons on Si photocathode, leading to the enhancement of solar hydrogen evolution efficiency. By doping phosphorus heteroatoms, CoSx materials showed an improved catalytic activity because of superior surface area and quantity of active sites. Furthermore, increased vacancies in unoccupied electronic states were observed, as more phosphorus atoms doped into CoSx co-catalysts. Although these vacant sites improved the capability to accept photoinduced electrons from Si photoabsorber, chemisorption energy of atomic hydrogen on catalysts was the dominant factor affecting in photoelectrochemical performance. We suggested that P-doped CoSx with appropriate doping quantities showed thermoneutral hydrogen adsorption. Excess phosphorus dopants in CoSx contributed to excessively strong adsorption with H atoms, causing the poor consecutive desorption ability of photocatalytic reaction. The optimal P-doped CoSx-decorated...