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

Abstract

• The O V -CQDs were modified on BiVO 4 for serving as superfast hole transfer channel. • 7.1-fold improvement of η surface (74.3%) was achieved for O V -CQDs/BiVO 4 at 0.65 V RHE . • The O V -CQDs efficiently promoted UV-vis light harvesting and bulk charge separation of BiVO 4 . • The O V -CQDs/BiVO 4 exhibited dramatically enhanced J of 4.01 mA cm −2 at 1.23 V RHE . The efficiency of hole extraction and transfer at electrode/electrolyte interface is one of the most important bottlenecks of BiVO 4 photoanodes for photoelectrochemical (PEC) water splitting. Here, a huge improvement of surface charge transfer efficiency ( η surface ) of BiVO 4 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/BiVO 4 shows the η surface value of 74.3% at 0.65 V vs. RHE (V RHE ), which is 7.1 and 3.3 times higher than BiVO 4 and CQDs/BiVO 4 , respectively. Besides, the O V -CQDs efficiently promote the bulk charge separation and UV-vis light harvesting of BiVO 4 . Therefore, the O V -CQDs/BiVO 4 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 BiVO 4 , 3.5 and 2.6 times higher than CQDs/BiVO 4 , respectively.