NiSi2/p-Si Schottky Junction Photocathode with a High-Quality Epitaxial Interface for Efficient Hydrogen Evolution

Si-based Schottky junction photoelectrodes have shown promising potential for photoelectrochemical (PEC) water splitting. One of the most challenging tasks to construct Si-based Schottky junction photoelectrodes with high efficiency is to obtain a high-quality metal/Si interface, which could reduce the interface defect density, increase the Schottky barrier height (SBH), and enable highly efficient charge transport. The epitaxial interface has been recognized as a nearly perfect electrical interface for the Si-based Schottky junction photoelectrodes. Here, we report the NiSi2/p-Si photocathode with a high-quality epitaxial interface, which is free of a disordered native SiO2 layer and has a low defect density. The dopant segregation strategy was utilized to introduce electrical dipoles at the NiSi2/p-Si interface, thereby increasing the SBH up to as high as 0.93 eV to obtain a high photovoltage. This epitaxial NiSi2/p-Si photocathode with Pt nanoparticles as hydrogen evolution reaction catalysts exhibited an excellent PEC performance with a high applied-bias photon-to-current efficiency of 5.2%. Furthermore, a full Si-based Schottky junction device was constructed by combining the epitaxial NiSi2/p-Si photocathode with a NiSi/n-Si photoanode to realize the overall water splitting under a low bias, illuminating a promising route for large-scale production of hydrogen from water.