Efficient Si/SiOx/ITO Heterojunction Photoanode with an Amorphous and Porous NiOOH Catalyst formed by NiCl2 activation for Water Oxidation

Abstract

Solar-driven water splitting with silicon photoelectrodes exhibiting high solar-to-fuel conversion efficiency is a promising way for producing hydrogen fuel in the future. In this study, a heterojunction photoanode was fabricated by the deposition of a thin indium tin oxide (ITO) layer on n-type silicon/native SiOx. A NiCl2-containing precursor was sprayed on the top of the photoanode, affording a NiO-Cl-OH catalyst; this NiO-Cl-OH catalyst was then activated to form an amorphous and porous NiOOH (a-NiOOH) catalyst, which exhibited enhanced performance. The fabricated Si/SiOx/ITO/a-NiOOH photoanode exhibited a low photocurrent onset potential of ∼0.98V vs. RHE, a high saturation photocurrent density of 36.98mA/cm2, a photocurrent density of 27.4mA/cm2 at the standard oxidation potential of water, and a photovoltage as high as 545mV under a solar illumination of 100mW/cm2. The photocurrent marginally decreased after 30h. These results suggested that such heterojunctions can replace homogeneous p–n junctions formed from Si doping for high photovoltage generation. In addition, porous a-NiOOH can improve the electrocatalytic performance of Si-based photoanodes.