(Invited) Si-Based Water Splitting Photoanodes Conjugated with Earth-Abundant Transition Metal-Based Catalysts

The development of a carbon-free hydrogen production method by photoelectrochemical (PEC) water splitting is a promising pathway to deal with the increased energy demands and deleterious environmental issues derived from the usage of fossil fuels. Silicon, which is the second most earth-abundant element and a small band-gap material, is an applicable candidate for an efficient solar water splitting photoelectrode. However, the stability of Si-based photoelectrodes hampers efficient water splitting because of its thermodynamic instability and etching of silicon surface. Until now, much research has been conducted to deal with the challenges of using Si to fabricate efficient and stable photoelectrodes. Over the decades, earth-abundant transition metal-based electrocatalysts (metals, sulfides, and hydroxides, phosphies) have been investigated intensively. We briefly introduce the photoelectrochemistry and important parameters for evaluating the performance of the Si photoelectrodes. We present our strategies to overcome the challenges of silicon by combining the advantages of transition metal-based electrocatalysts, which are cost-effective, stable, and highly active for both oxygen evolution and hydrogen evolution reactions. To realize spontaneous water splitting, we introduce Si-based PEC-photovoltaic cells using transition metal-based materials.