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

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, BiVO 4 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 BiVO 4 /ferroelectric BiFeO 3 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 BiVO 4 . BiVO 4 /BiFeO 3 also greatly decreases charge recombination rate from 17 s −1 to 0.6 s −1 in comparison to the plain BiVO 4 by ~28 times. The PEC performance of BiVO 4 /BiFeO 3 can also be manipulated based on the direction of self-polarization in BiFeO 3 . Moreover, BiVO 4 /BiFeO 3 shows much better stability than that of the BiVO 4 as well as BiVO 4 /Co-Pi. It is discovered that the PEC performance enhancement mechanism is attributed to the BiFeO 3 passivation for a bifunctional film as a buffer layer to significantly reduce charge recombination while as an efficient catalyst to boost charge separation/transfer. [ABSTRACT FROM AUTHOR]