A high-efficiency mediator-free Z-scheme Bi_2MoO_6/AgI heterojunction with enhanced photocatalytic performance

摘要

A high-efficiency Z-scheme Bi_2MoO_6/VAgI heterojunction was designed and fabricated via in situ growth of AgI on Bi__2MoO_6. Its photocatalytic activity was investigated with the degradation of malachite green (MG). After 40 min of visible light irradiation, near complete degradation of MG (20 mg/L) occurred when BA11 (Bi_2MoO_6:AgI = 1:1, 2.0 g/L) was present, while only 29.0% and 49.7% of the MG could be degraded in the presence of Bi_2MoO_6 and AgI, respectively. The excellent photocatalytic activity of BA11 results from strong visible light absorption and the low recombination efficiency of photogenerated electron-hole pairs induced by the formation of heterojunction. Density function theory (DFT) calculations revealed that the formation of built-in electric field at the interface between Bi_2MoO_6 and Agl facilitates the effective separation and transfer of photogenerated charge carriers. Results of reuse experiments indicated that the heterostructured photocatalyst has excellent stability. Radical scavenging experiments and electron spin resonance spectra showed that superoxide radicals (·O_2~-) and hydroxyl radicals (·OH) were the major reactive oxygen species in the photocatalytic system. The photocatalytic degradation pathway of MG was proposed based on the organic degradation intermediates detected. These findings demonstrate that the mediator-free Z-scheme Bi_2MoO_6/AgI heterojunction could serve as a promising photocatalyst in photocatalytic treatment of organic pollutants.