Tailored NiFe Catalyst on Silicon Photoanode for Efficient Photoelectrochemical Water Oxidation

yy The decoration of n-type silicon (n-Si) with bimetallic NiFe nanoparticles has been shown to be an effective approach in achieving efficient photoelectrochemical (PEC) water oxidation. However, the ratio of Ni/Fe was not precisely controlled in the previous studies and the respective effects of Ni and Fe on the PEC performance have not been systematically investigated. In this work, dual-source electron beam evaporation is employed to deposit NiFe nanoparticles on n-Si with precisely controlled Ni/Fe ratios. The NiFe/SiOx/n-Si photoanode records an applied bias photon-to-current efficiency (ABPE) of 3.03 +/- 0.10% with a Ni/Fe ratio of 3:1. However, the stability of the photoanode decreases with higher Fe content, which is ascribed to the leaching of Fe catalytic sites. With the addition of Fe ions into the electrolyte, the ABPE is maintained at 3.12 +/- 0.04% and the stability is significantly improved. Our results highlight a potential method to achieve efficient and stable PEC water oxidation with this simple device architecture.