Substantially enhanced front illumination photocurrent in porous SnO2 nanorods/networked BiVO4 heterojunction photoanodes

Abstract

BiVO₄ is a promising photoanode for photoelectrochemical applications owing to its suitable band edge position for oxygen evolving reactions. High photocurrent under front illumination is very much essential to design tandem structures with a wireless configuration. However, the performance of BiVO₄ under front illumination is limited due to poor charge transport properties. Here, we show that network-like BiVO₄ coupled with porous SnO₂ nanorods (NRs) is a promising model to enhance the front illumination performance. A very high photocurrent density of 5.6 mA cm⁻² and 5.5 mA cm⁻² has been obtained from the front and back illumination at 1.23 V vs. the reversible hydrogen electrode, respectively. We demonstrate that the appropriate nanostructuring of SnO₂ NRs/BiVO₄ is the underlying technology to tune the performance under directional illumination. The SnO₂ NRs/BiVO₄ exhibits a maximum incident photon to current efficiency of ∼80% under front and back illumination. A systematic study reveals that the optimized network like BiVO₄ coated on porous SnO₂ NRs synergistically boosts both the charge separation and transfer efficiencies of the photoanode resulting in a significantly high photocurrent for illumination on either side. This work provides a direction to achieve enhanced photocurrent during front and back side illumination in order to realize a wireless tandem configuration.