Oxygen vacancy-abundant carbon quantum dots as superfast hole transport channel for vastly improving surface charge transfer efficiency of BiVO4 photoanode

The efficiency of hole extraction and transfer at electrode/electrolyte interface is one of the most important bottlenecks of BiVO4 photoanodes for photoelectrochemical (PEC) water splitting. Here, a huge improvement of surface charge transfer efficiency (eta(surface)) of BiVO4 photoanode was achieved by surface modification of oxygen vacancy-abundant carbon quantum dots (O-V-CQDs), in which the O-V-CQDs serve as superfast hole transport channel for the fact that the abundant O-V in O-V-CQDs could induce the outward driving force for hole trapping and migration at electrode/electrolyte interface. The O-V-CQDs/BiVO4 shows the eta(surface) value of 74.3% at 0.65 V vs. RHE (V-RHE), which is 7.1 and 3.3 times higher than BiVO4 and CQDs/BiVO4, respectively. Besides, the O-V-CQDs efficiently promote the bulk charge separation and UV-vis light harvesting of BiVO4. Therefore, the O-V-CQDs/BiVO4 exhibits remarkable photocurrent densities of 2.76 mA cm(-2) at 0.65 V-RHE and 4.01 mA cm(-2) at 1.23 V-RHE, which are 12.5 and 3.4 times higher than BiVO4, 3.5 and 2.6 times higher than CQDs/BiVO4, respectively.

Automated summary

Surface modification of oxygen vacancy-abundant carbon quantum dots significantly enhances the surface charge transfer efficiency of BiVO4 photoanodes, leading to improved bulk charge separation and light absorption. This results in significantly higher photocurrent densities compared to BiVO4 and carbon quantum dots modified BiVO4.