Converting and storing solar energy has been regarded as a promising approach to address the current global reliance on fossil fuels. The generation of hydrogen from water using sunlight can form potentially the basis of a clean and renewable source of energy. Solar water splitting system requires stable light-absorbing electrodes for both the oxidative and reductive half-reactions. However, the kinetically slow oxygen evolution reaction (OER) is a bottle-neck process for producing sustainable solar-driven fuels using water.

Silicon has a suitable band gap (1.12 eV) to absorb the wide range of the solar spectrum and has high carrier mobility. For this reason, silicon is an attractive candidate among the various materials such as transition metal oxides and semiconductors. Since the silicon photoanode is unstable at electrolyte and suffers from fast photocorrosion due to the position of thermodynamic redox potentials, the solar to hydrogen conversion efficiency of bare silicon photoanode is largely suppressed. To solve those problems of silicon, recent studies on silicon photoanode has focused on designing a surface passivation layer that protects against chemical and photo-induced corrosion without degrading the inherent photoactive ability of silicon and promotes the chemical adsorption of water molecules to lower the overpotential at the solid/liquid interface.

Herein, we report the synthesis and photoelectrochemical properties of multifunctional cobalt based catalysts on a n-type silicon photoanode by using facile electrodeposition. This method not only significantly reduces the synthesis time and costs, but also easily control reaction by changing applied voltage or current. The solution-processed n-Si photoanode showed large photovoltage and superior catalytic behavior. By using efficient oxygen evolution catalysts, onset potential shifted to cathodic direction, leading to highly efficient Si-based photoanodes.