Highly efficient Z-scheme structured visible-light photocatalyst constructed by selective doping of Ag@AgBr and Co3O4 separately on {010} and {110} facets of BiVO4: Pre-separation channel and hole-sink effects

To improve the visible-light photocatalytic activity and photo-carriers separation of BiVO 4 , highly efficient Z-scheme structured visible-light photocatalyst Ag@AgBr/BiVO 4 /Co 3 O 4 was constructed by selective doping of Ag@AgBr and Co 3 O 4 on {010} and {110} facets of BiVO 4 . Due to the different energy levels of conduction band (CB) and valence band (VB) between {010} facet and {110} facet, BiVO 4 could act as the ‘pre-separation channel’ to achieve spatial charge separation. Such pre-separation channel effect improved photo-electrons transfer from BiVO 4 {010} facets to electron mediator (Ag°) for subsequent recombination with holes of AgBr. Thus, the photo-induced electrons of AgBr could be accumulated on CB for reduction of O 2 to O 2 − . On the other hand, holes of BiVO 4 accumulated on {110} facets were captured by deriving-hole-type co-catalysts Co 3 O 4 for organics oxidation. In addition, Ag° not only served as the electron mediator of Z-scheme but also improve the visible-light utilization due to SPR-effect. Being attributed to the synergistic effect of pre-separation channel and deriving-hole-type co-catalysts, Z-scheme structured Ag@AgBr/BiVO 4 /Co 3 O 4 (0.15 wt%) achieved high photodegradation rate of organics. Even after 9th cycles, Ag@AgBr/BiVO 4 /Co 3 O 4 (0.15 wt%) could still photodegraded more than 90% of OTC within 24 min. DRS, PL and photoelectrochemical analyses also confirmed the improvement of visible-light utilization and charge separation of Ag@AgBr/BiVO 4 /Co 3 O 4 . The radical trapping experiments and EPR demonstrated that both superoxide radical ( O 2 − ) and holes (h + ) were main active species for organics photodegradation. In summary, this work not only constructed a highly efficient Z-scheme structured visible-light photocatalyst, but also provided a new method to diminish the photo-carriers recombination by pre-separation channel and hole-sink effects.