Z-scheme Fe2(MoO4)3/Ag/Ag3PO4 heterojunction with enhanced degradation rate by in-situ generated H2O2: Turning waste (H2O2) into wealth (•OH)

Ag3PO4-based photocatalysts have been deeply studied in environmental remediation; however, two problems limited their further application: photocorrosion and quenching effect by in-situ generated H2O2. To addressed these two questions simultaneously, Fe2(MoO4)3 was coupled with Ag3PO4 to construct Z-scheme Fe2(MoO4)3/Ag/Ag3PO4 heterojunction driven by internal-electric-field. The rhodamine B degradation rate of heterojunction was 254 and 7.0 times higher than those of Fe2(MoO4)3 and Ag3PO4, respectively. The outstanding photoactivity was due to the high visible-light harvest, low interface resistance, high separation efficiency of charge carriers, long lifetime of hole (h+) and electron (e-), well-preserved oxidation potential of h+, and especially photocatalytic produced H2O2 inside the system. The in-situ generated H2O2 was fully activated to be •OH on the Fe2(MoO4)3 surface via a Fenton reaction, leading to the elimination of quenching effect on h+ and e-, and generation of more •OH. Additionally, in Z-scheme heterojunction, e- transferred from Ag3PO4 to Fe2(MoO4)3, avoiding the accumulation on Ag3PO4 surface, and hence suppressing the photocorrosion. As a result, 91.2% of degradation efficiency remained after 5 cycles. This paper provides a new method to simultaneously increase the degradation rate by utilizing the in-situ generated H2O2 and improve the stability of Ag3PO4 via constructing a Z-scheme heterojunction.