Cascading Interfaces Enable N-Si Photoanode for Efficient and Stable Solar Water Oxidation.

The interfaces with multi-functions for the promoted solid/solid interfacial charge transfer dynamics and the accelerated solid/electrolyte interfacial water redox reaction kinetics are determinative to the photoelectrodes achieving high performances for photoelectrochemical (PEC) water splitting. In this work, the well-designed cascading interfaces are introduced in the n-Si photoanode, which is effectively protected by an atomic layer deposited CoOx thin layer for stabilizing the n-Si photoanode and then coated with an earth-abundant NiCuOx layer for catalyzing water oxidation reaction. Furthermore, the formed n-Si/CoOx/NiCuOx 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/CoOx/NiCuOx cascading interfaces. Moreover, at the NiCuOx/electrolyte interface, an in-situ electrochemically formed NiCu(OH)x/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.