Cascading Interfaces Enable n-Si Photoanodes for Efficient and Stable Solar Water Oxidation.

Interfaces with multifunctions for promoted solid/solid interfacial charge-transfer dynamics and accelerated solid/electrolyte interfacial water redox reaction kinetics are determinative for the photoelectrodes achieving high performances for photoelectrochemical (PEC) water splitting. In this work, well-designed cascading interfaces are introduced in the n-Si photoanode, which is effectively protected by an atomic layer-deposited CoO thin layer for stabilizing the n-Si photoanode and then coated with an earth-abundant NiCuO layer for catalyzing the water oxidation reaction. Furthermore, the formed n-Si/CoO /NiCuO triple junction could generate a large band bending to provide a considerable photovoltage for promoting the photoinduced charge-transfer and separation processes at the n-Si/CoO /NiCuO cascading interfaces. Moreover, at the NiCuO /electrolyte interface, an in situ electrochemically formed NiCu(OH) /NiOOH active layer facilitates the water oxidation reaction kinetics. This study demonstrates an alternative approach to stabilize and catalyze n-Si-based photoanodes with cascading interfaces for efficient solar water oxidation.