Metal-insulator-semiconductor (MIS) photoelectrodes offer a simple alternative to the traditional semiconductor-liquid junction and the conventional p-n junction electrode. Highly efficient MIS photoanodes require interfacial surface passivating oxides and high workfunction metals to produce a high photovoltage. Herein, we investigate and analyze the effect of interfacial oxides and metal workfunctions on the barrier height and the photovoltage of a c-Si photoanode. We use two metal components in a bimetal contact configuration and observe the modulation of the effective barrier height and the resulting photovoltage as a function of the secondary outer metal. The photovoltage shows a strong linear dependence by increasing the inner metal workfunction, with the highest photovoltage achieved by a MIS photoanode using a platinum inner metal. We also found that coupling a thin aluminium oxide with an interfacial silicon oxide and controlling the oxide thickness can significantly improve the photovoltage of an MIS junction photoanode.

Photoelectrochemical (PEC) water splitting is a sustainable approach to produce a renewable fuel by harvesting the energy of the Sun to split water to form hydrogen and oxygen. In order to drive the water splitting reaction efficiently, substantial ohmic losses due to poor ionic conductivity of the electrolyte should be avoided, and therefore the reaction should be carried out at an extreme electrolyte pH. Herein we demonstrate the photoelectrochemical activity of an amorphous silicon carbide (a-SiC) photocathode for solar hydrogen evolution using an ultrathin nickel (Ni) film coupled with a nickel molybdenum catalyst (Ni-Mo) in a highly alkaline solution (pH 14). The incorporation of the Ni film coupled with Ni-Mo nanoparticles increases the number of active sites and therefore improves the kinetics of the hydrogen evolution reaction. Additionally, we report the influence of the catalyst configurations on the ohmic and solid liquid junction behavior on semiconducting interfacial layers. The a-SiC photocathode coated with the Ni/Ni-Mo dual-catalyst produces a photocurrent density of -14 mA cm^-2 at 0 V vs. RHE using only cheap and abundant materials. This photocurrent is the highest recorded value from an amorphous-Si-based photocathode, and is achieved with a total film thickness of less than 150 nm.