Near-complete charge separation in tailored BiVO4-based heterostructure photoanodes toward artificial leaf

Abstract As an artificial leaf, a tandem device for zero-bias solar water splitting is a capable solution for practical hydrogen production. Despite a promise, poor charge transport of BiVO4 hampers photoelectrochemical performances under front-side illumination, which is a hindrance to the tandem system. Herein, we design a new photoanode comprising nanoporous BiVO4 and SnO2 nanorods focused on the charge separation via structural and interfacial engineering. BiVO4/SnO2 photoanode exhibits not only remarkable charge separation efficiency of 97% but also, by loading NiFe as a co-catalyst for water oxidation, high photocurrent density of 5.61 mA cm-2 at 1.23 V versus the reversible hydrogen electrode under front-side 1 sun illumination. Consequently, a tandem cell comprising NiFe/BiVO4/SnO2 photoanode and perovskite/Si tandem solar cell generates an operating photocurrent density of 5.90 mA cm-2 with a solar-to-hydrogen conversion efficiency of 7.3% in zero-bias. This work would be a significant step to develop spontaneous solar hydrogen production.