Constructing a novel multi-hierarchical TiO2/g-C3N4/Ag-AgBr photocatalyst with dual Z-scheme heterojunction utilizing Ag as the charge transfer mediator

Abstract

Constructing multi-heterojunction photocatalysts with multi-sources for carrier generation and with multi-channels for carrier transmission is one of the effective methods for enhancing the photocatalytic activity. Here, a novel TiO2/g-C3N4/Ag-AgBr (TCNAAB) multi-heterojunction photocatalyst was successfully constructed by depositing Ag-AgBr nanoparticles onto 3D spherical TiO2/g-C3N4. With the optimal ratio of TiO2, g-C3N4 and Ag-AgBr, the TCNAAB-50 composite had the highest H2 evolution activity and generated 940.5 μmol g−1 of H2, which was 8.24 times and 2.72 times higher than that generated by single TiO2 and binary TiO2/g-C3N4, respectively. Meanwhile, TCNAAB-50 also exhibited the highest photocatalytic activity toward methyl orange (MO) with the degradation efficiency of 77.6% under LED light. The enhanced photocatalytic performance is attributed to the multi-sources for carrier generation and the multi-channels for carrier transmission of the constructed multi-heterojunction, which help to effectively enhance the light absorption efficiency and the carrier separation and transmission. Based upon PL spectra, photoelectrochemical properties, radical quenching experiments and electron spin resonance spectra, a novel double Z-scheme heterojunction bridged by silver was proposed. The design of high-efficiency multi-heterojunction with multi-carrier excitation sources and multi-carrier transmission channels can be employed in improving the photocatalytic activity of single or binary component photocatalysts.