Efficient Solar Water Splitting via Enhanced Charge Separation of the BiVO₄ Photoanode

Bismuth vanadate (BiVO4) with a narrow band gap was considered as one of the most desirable matrices for the photoelectrode in a photoelectrochemical (PEC) water splitting system. However, the serious recombination rate of photogenerated charges in BiVO4 causes the practical PEC efficiency to be significantly lower than the theoretical value. Herein, we provide a simple route for modification of BiVO4-based photoanodes with Ni-NDAD to promote charge separation and accelerate water oxidation kinetics. As a result, the Ni-NDAD/BiVO4 photoelectrodes deliver a high photocurrent density of 5.6 mA cm–2 (1.23 V vs reversible hydrogen electrode) and an incident photon-to-current conversion efficiency of 80% (460 nm), which were around 3.5- and 5.3-fold higher than that of pristine BiVO4, respectively. In addition, the introduction of Ni-NDAD on BiVO4 could trap photogenerated holes transferred from BiVO4, thus allowing significant acceleration of water oxidation kinetics and overall improvement in the performance of the whole BiVO4-based PEC water splitting system. Furthermore, the Ni-NDAD/BiVO4 photoanode also displayed high PEC catalytic activity for chlortetracycline (CTC) removal in the presence of persulfate (PS), achieving an 89.19% degradation efficiency within 30 min. This work provides a promising design strategy for efficient photogenerated charge separation to improve PEC water splitting and organic contaminant removal.