Self-driven hematite-based photoelectrochemical water splitting cells with three-dimensional nanobowl heterojunction and high-photovoltage perovskite solar cells

Abstract

Solar-driven photoelectrochemical (PEC) water splitting is a clean and powerful approach for renewable hydrogen production. The PEC performance of hematite (α-Fe2O3) is largely limited by its short hole diffusion length, which imposes restrictions on increasing the thickness for enough light absorption. In this work, we report a well-engineered three-dimensional (3D) Fe2O3/NTO (Nb-doped SnO2) nanobowl heterojunction for PEC electrode, driven by a high-photovoltage perovskite solar cell (PSC), has boosted the efficiency greatly. The 3D heterojunction is made of an ultrathin Ti-doped hematite layer deposited on a periodic NTO nanobowl array. This PEC electrode, not only significantly improves the light absorption of the ultrathin hematite, but also enhances the interface contact. As a result, it exhibits ∼3.16 mA cm−2 photocurrent at 1.23 V vs the reversible hydrogen electrode with the Co–Pi cocatalyst. The tandem cell self-biased with a high-photovoltage PSC delivers up to 3.25% solar-to-hydrogen conversion efficiency, higher than those of state-of-the-art hematite-based PEC cells.