Important Role of Phosphorus in Boosting Photoelectrochemical Properties of BiVO₄/ZnFe-MOF Photoanodes

This study investigates the enhancement of BiVO4 photoanodes with a ZnFe-MOF cocatalyst, emphasizing the crucial role of phosphorus in boosting their photoelectrochemical properties. It is demonstrated that ZnFe-MOFs effectively improve the photocurrent density and photoconversion efficiency of BiVO4. Further analysis reveals that phosphorus within ZnFe-MOFs not only stabilizes the MOF structure but also significantly enhances electron transfer on the BiVO4 surface and promotes charge separation during photoexcitation. At 1.23 V vs RHE, the photocurrent density of BiVO4/ZnFe-MOFs is 2.07 mA cm–2, while that of BiVO4/ZnFe-MOFs/K2HPO4 reaches 3.41 mA cm–2, which are 1.71 times and 3.1 times the photocurrent density of the original BiVO4 photoanode, respectively. The photocurrent density of BiVO4/ZnFe-MOFs/K2HPO4 (3.41 mA cm–2) outperforms that of other phosphorus sources, such as KH2PO4 (2.67 mA cm–2), Na3PO4 (2.43 mA cm–2), Na5P3O10 (2.21 mA cm–2), and NH4H2PO4 (2.01 mA cm–2). Additionally, the BiVO4/ZnFe-MOF/K2HPO4 photoanode has a stronger stability for water oxidation at 1.23 V vs RHE, and its photocurrent density remains 81% of the initial current after 11000 s, while pure BiVO4 only retains 45% of the initial current. The research offers new ideas for an efficient electrode design to improve water splitting efficiency.