In situ unravelling surface plasmon resonance subject-object role of BiVO@Ag in photocatalytic water splitting.

Surface plasmon resonance (SPR) of noble metal particles has been recognized to play a significant role in photocatalysis. We designed the BiVO@Ag system by photo-deposition to prove the special role of Ag nanoparticles (NPs) in promoting water splitting. The BiVO@Ag considerably increases light absorption by the SPR effect of Ag NPs. A strong interface effect in BiVO@Ag-5 is effectively demonstrated through in situ vibration frequency variation of VO bonds from 826.1 cm to 820.9 cm. Loaded Ag NPs in BiVO improve slightly the hot electron lifetime (1.80 fs) compared with BiVO (1.53 fs). Ag NPs significantly raise the conduction band potential of BiVO@Ag system and evidently enhance the electrochemical specific surface area. The BiVO@Ag also exhibits significant thermal effects when illuminated with a light source (>520 nm). However, BiVO@Ag does not exhibit photocatalytic hydrogen evolution ability as using above light source, indicating that the pyroelectric current does not directly promote the photocatalytic hydrogen evolution performance of BiVO@Ag. Using a light source (<520 nm) to excite and filter out the photothermal effect of BiVO@Ag-5, an obvious reduction of hydrogen evolution (from 72.1 μmol to 18.3 μmol) can happen. The excited SPR effect with a light source (>520 nm, filter out the intrinsic absorption of BiVO matrix) proves that the SPR effect can only accelerate the hydrogen evolution rate of the system. The increase in temperature cannot significantly improve the photocatalytic hydrogen evolution rate of BiVO@Ag-5. Ab initio molecular dynamics calculations based on solvation models suggest that the surface of BiVO mainly provides the role of water decomposition, while Ag NPs mainly provide the role of photocatalytic hydrogen evolution. These findings provide a unique perspective to understand the photocatalytic water splitting behaviors, which are of general significance in various energy conversion reactions.