A novel BiVO4/DLC heterojunction for efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting is a promising technology to produce renewable hydrogen, which still faces problems of low photoelectric efficiency and instability. This work introduces a novel Type II heterojunction consisting of BiVO 4 thin film and diamond-like carbon (DLC) to the PEC system as a photoanode and achieves an increased PEC water-splitting activity. Compared to the pure BiVO 4 , the BiVO 4 /DLC heterojunction has an increased photocurrent density from 0.79 mA cm −2 to 2.39 mA cm −2 at 1.23 V vs RHE, and the IPCE from 4.8 % to 23.4 %. After 120 min (180 cycles) of PEC water splitting, the BiVO 4 /DLC heterojunction retains up to 82.3 % of the initial photocurrent density value, while the pure BiVO 4 has only 33.99 % remaining under the same conditions. Furthermore, the PEC system of BiVO 4 /DLC reaches the evolution rate of hydrogen of over 0.32 mmol h −1  cm −2 , which is much higher than that of its counterparts. We ascribe the enhancement in PEC performance to the Type II heterojunction photoanodes that greatly promote carrier mobility and reduce the recombination rate of electron-hole pairs. We also identify that the band bending and depletion layer are the main reasons for the decrease in charge transfer and interface resistance. It is demonstrated that the sp 2 carbon phase in DLC acts as a conductive channel to improve the separation and migration efficiency of free carriers, while the sp 3 carbon phase provides stable support and passivation effect to the photoanode, thereby leading to an enhancement for both PEC water splitting performance and the long-time stability. This work provides an effective way to improve the BiVO 4 photoanode-based PEC water-splitting systems.