Solar hydrogen conversion via photoelectrochemical water splitting is an important technology for energy and environment sustainability. Since the pioneering work of Fujishima and Honda in 1972, tremendous research on semiconductor-based photoelectrochemical water splitting has yielded better understanding of the processes as well as encouraging development of high efficiency photoelectrodes for solar hydrogen generation. In this talk, some recent progresses in heterostructures of α-Fe₂O₃and p-Si for photoelectrochemical solar water splitting in our group will be introduced.

Given the narrow band gap enabling excellent optical absorption, increased charge carrier density and accelerated surface oxidation reaction kinetics become the key points for improved photoelectrochemical performances for water splitting over α-Fe₂O₃ photoanodes. By engineering the surface structures of α-Fe₂O₃ nanorods with Ag_xFe_2-xO₃, TiO₂ and HfO₂overlayers, the surface charge recombination was greatly inhibited and the surface water oxidation kinetics were efficiently accelerated, resulting in remarkable enhancement in PEC water splitting performances.

p-Si has captured intensive attentions for solar hydrogen conversion due to its high natural abundance and narrow band gap (~1.1 eV). However, the slow charge-transfer kinetics at the p-Si/electrolyte interface lead to large overpotentials for hydrogen evolution and electrocatalysts are always necessary. Recently, we successfully engineered the surface energetics of p-Si with n-WO₃ overlayer and Ni molecular complexes, which gave rise to a great anodic shift of up to 300 mV in onset potential for photocathodic water reduction.