Multifunctional Nickel Film Protected n-Type Silicon Photoanode with High Photovoltage for Efficient and Stable Oxygen Evolution Reaction

n-type silicon (n-Si) is a promising photoanode candidate for photoelectrochemical (PEC) water splitting. However, severe chemical corrosion, sluggish reaction kinetics as well as extremely low photovoltage are critical limitations hampering its PEC performance. This paper describes the introduction of a metallic nickel (Ni) thin film as a multifunctional layer that 1) forms a Schottky junction to extract a high photovoltage, 2) provides an electrocatalytic surface for oxygen evolution reaction (OER), and 3) protects Si against corrosion. Upon introducing a high-quality Al2O3 tunneling layer to optimize the Si/Ni interface and loading nickel oxide hydroxide to further accelerate the OER, this metal-insulator-semiconductor junction photoanode achieves a record high photovoltage of 640 mV and energy conversion efficiency of 3% in n-Si based photoanodes without np or np(+) buried homojunction, yielding an air mass 1.5G photocurrent density of approximate to 28 mA cm(-2) at 1.23 V (vs reversible hydrogen electrode) for oxygen evolution in alkaline solution with a stability of more than 80 h.