Highly efficient BiVO4 single-crystal photocatalyst with selective Ag2O-Ag modification: orientation transport, rapid interfacial transfer and catalytic reaction.

Coupling crystal-facet engineering with selective interfacial modification has been demonstrated to be an effective strategy to enhance the photocatalytic performance of semiconductor photocatalysts. For instance, BiVO4 exhibited excellent photocatalytic activity when Pt cocatalyst was selectively modified on the (010) facet of BiVO4 single-crystal photocatalyst with exposed (010) and (110) facets. In view of the high cost and rarity of metallic Pt, it was desirable to discover low-cost electron cocatalysts that show comparable activity with Pt. In the study, Ag2O-Ag as a novel and highly efficient electron cocatalyst was selectively modified on the (010) facet of single-crystal BiVO4 photocatalyst via facile photodeposition of metallic Ag and its subsequent partial oxidation to Ag2O via low-temperature calcination (100-400 °C). In detail, Ag was selectively modified on the electron-rich (010) facet of BiVO4 single crystal, while Ag2O was selectively formed on the Ag surface, resulting in the formation of Ag2O-Ag/BiVO4 photocatalyst. As a result, Ag2O-Ag/BiVO4 exhibited nearly comparable activity with Pt/BiVO4, but clearly higher activity than Ag/BiVO4 or BiVO4 alone. The enhanced performance was ascribed to the synergistic effect of crystal-facet engineering of BiVO4 and selective modification of Ag2O-Ag electron cocatalyst. In detail, the single crystal structure of BiVO4 results in the orientation transport of photogenerated carriers, while metallic Ag effectively transfers photogenerated electrons of BiVO4 and then, Ag2O as the active site accelerates the reduction of dissolved oxygen. Considering that our present synthetic strategy is facile, controllable and economical, this study provides insight into the design and synthesis of highly efficient semiconductor photocatalysts.