Bi-functional ferroelectric BiFeO3 passivated BiVO4 photoanode for efficient and stable solar water oxidation

Abstract Photoelectrochemical (PEC) devices have become one of the most attractive clean energies due to its potential high efficiency and simplicity but it is very challenging to make a highly efficient and stable practical device. Up to date, BiVO4 as the most promising ternary metal-oxide photoanode can only achieve a photocurrent of no more than 1.0 mA cm−2, which is far below its theoretical value (7.5 mA cm−2), and is mainly caused by its high charge recombination from defects and sluggish water oxidation kinetics. Herein we fabricate a BiVO4/ferroelectric BiFeO3 composite photoanode by a surface passivation approach to greatly enhance photocurrent by ~4.4 times plus ~400 mV negative shift of the onset potential than the plain BiVO4. BiVO4/BiFeO3 also greatly decreases charge recombination rate from 17 s−1 to 0.6 s−1 in comparison to the plain BiVO4 by ~28 times. The PEC performance of BiVO4/BiFeO3 can also be manipulated based on the direction of self-polarization in BiFeO3. Moreover, BiVO4/BiFeO3 shows much better stability than that of the BiVO4 as well as BiVO4/Co-Pi. It is discovered that the PEC performance enhancement mechanism is attributed to the BiFeO3 passivation for a bifunctional film as a buffer layer to significantly reduce charge recombination while as an efficient catalyst to boost charge separation/transfer.