Surface Phosphorization for the Enhanced Photoelectrochemical Performance of an FeO/Si Photocathode

Transition metal phosphates (TMPs) are regarded as efficient co-catalysts for photoanodes, but they are rarely applied in hydrogen production reactions. In this work, iron phosphate (FePi), a co-catalyst for hydrogen production, is introduced onto the FeO surface by facile surface phosphorization under low-temperature conditions. The surface FePi leads to a shift of the onset potential by +201 mV and an increase in the photocurrent density by more than 10 mA cm at 0 V for the FeO/p-Si photocathode in a strong alkaline electrolyte. The role of FePi stems from the smaller transfer resistance, efficient photogenerated carrier separation and electron injection, and preferable H* adsorption energy, as suggested by Kelvin probe force microscopy and density functional theory (DFT) calculation. The surface phosphorization presents a facile and attractive strategy for the treatment of transition metal oxide catalyzed photocathodes for green hydrogen production.