The synergistic cooperation of carbon quantum dots and Fe MOF for the greatly improved charge separation efficiency of MW:BVO

Bismuth vanadate (BiVO4) is a promising photoelectrochemical (PEC) water splitting material. However, its high carrier recombination rate, slow surface reaction kinetics, and narrow light absorption range have been major bottleneck problems. In this work, a novel composite material, MW:BVO@NH2-MIL-101(Fe) (Fe MOF)@CQDs, was successfully synthesized by simultaneous modification of the MW:BVO(BVO co-doped with Mo and W) surface with carbon quantum dots (CQDs) and Fe MOF nanoparticles. The introduction of Fe MOF and CQDs as co-catalysts significantly improved the photocurrent density of MW:BVO by nearly 5 times. CQDs, as a non-toxic and safe green material, exhibit excellent electron transfer ability and up-conversion luminescence characteristics, which help to suppress the recombination of photo-generated carriers and broaden the light absorption spectrum. The incorporation of CQDs resulted in a significant increase in the photocurrent density of MW:BVO@Fe MOF@CQDs up to 5.9mAcm-2, while enhancing its light absorption ability. This enhancement can be attributed to two factors: firstly, the introduction of Ov defects due to the co-catalysis of CQDs and Fe MOF can greatly improve the OER reaction kinetics; secondly, the introduction of Fe MOF and CQDs can provide more active sites for oxygen evolution, and the synergistic effect of the dual co-catalysts promotes the separation of photogenerated carrier pairs, which may account for the significant improvement in the PEC performance of MW:BVO@Fe MOF@CQDs. Therefore, this work provides some interesting new insights for the construction of efficient photocatalytic anodes for PEC applications.