RESUMEN
Visible light-driven H2O2 production presents the unique merits of sustainability and environmental friendliness. The size of noble metal nanoparticles (NPs) determines their dispersion and electronic structure and greatly affects their photocatalytic activity. In this work, a series of sized Au NPs over C3N4 were modulated for H2O2 production. The results show that there is a volcanic trend in H2O2 with the decrease of Au particle size, and the highest H2O2 production rate of 1052 µmol g-1 h-1 is obtained from medium-sized Au particles (â¼8.7 nm). The relationship between structure and catalytic performance is supported by experimental and theoretical methods. (1) First, medium-sized Au NPs promote photon absorption, and have a suitable built-in electric field at the heterojunction, which can be successfully tuned to achieve a more efficient h+-e- spatial separation. (2) Second, medium-sized Au NPs enhance O2 adsorption, and create selective 2e- O2 reduction reaction sites. (3) Particularly, medium-sized Au NPs promote the desorption of produced H2O2 and inhibit H2O2 decomposition, finally leading to the highest H2O2 selectivity. Excellent catalytic performance will be obtained by finely optimizing the particle size in a certain range. This work provides a new idea for preparing high efficiently photocatalysts for H2O2 production.
RESUMEN
Photoredox catalysis under visible light has been recorded as a potential and reassuring recipe for organic synthesis. More and more heterojunction catalysts have appeared in people's fields of vision, especially those with S-scheme heterojunction structures. The S-scheme heterojunction structure of a photocatalyst can remarkably improve its photocatalytic efficiency. Here, an S-scheme α-Fe2O3/Cu2O heterojunction photocatalyst was designed and fabricated for the primary amine oxidative coupling reaction. On account of that, the S-scheme structure effectively separated the photogenerated electron-hole pairs and enhanced the photoredox ability of the photocatalytic system. The α-Fe2O3/Cu2O composite could also enhance the reactivity to a large extent. This work will provide new insight into the design of photocatalysts with a more reasonable structure and higher performance.
RESUMEN
The disposal of the Cr containing tannery sludge has become a serious environmental problem in China, which has attracted increasing attention. However, experimental and theoretical research is still needed. We developed a feasible route to synergistic immobilization the Cr in tannery sludge into the spinel-based phases by addition of ZnO and TiO2. ZnO and Cr3+ can form stable spinel-based phase, and TiO2 can suppress the formation of Cr6+. The significantly synergistic effect between ZnO and TiO2 promoted the immobilization of Cr in tannery sludge and reduce the leaching of the chromium in the annealed sludge. The oxidation of Cr3+ to Cr6+ in the presence of alkaline substances has been elucidated by density functional theory, and it is revealed that the electrons from the Cr-d orbit jump to the Ca-d and directly transform into the O2.