Steering electron transfer using interface engineering on front-illuminated robust BiVO4 photoanodes

Front solar illumination on BiVO4 is becoming important to design tandem structures in photoelectrochemical (PEC) water splitting. However, the interfacial recombination of BiVO4/substrate (e.g. FTO) is more serious than the bulk/surface recombination, which influences the electron transfer to the back side for hydrogen reaction. The BiVO4 electrode therefore requires back illumination to obtain the best photoresponse. In this context, we proposed a universal strategy by applying a PdO layer functionalized SnO2 interface as a useful electron transport layer to strikingly reduce the interface recombination. A trace amount of Pd was doped in the bulk BiVO4 to modify the electronic structure by inducing a stronger dopant-host interaction than that of the surface-modified electrode and homogenous doping. The BiVO4/PdO electrodes exhibited similar PEC performance under both front and back illumination. The champion cocatalyst-free photoanode showed a record-high photocurrent of 4.90 mA cm(-2) at 1.23 V-RHE with a low onset potential of 0.15 V-RHE in borate buffer electrolyte under AM 1.5 G front-illumination, accompanying with solar conversion efficiency of 1.72% at 0.6 V-RHE. Equally importantly, a sustained long-term photostability over 80 h was achieved, which is the best performance and stability reported among the cocatalyst-free BiVO4 photoelectrodes from front illumination. This work will open a new avenue for high-stability-performance photoelectrode design.