Abstract
Light-driven production of hydrogen peroxide (H2O2) is a green and sustainable way to achieve solar-to-chemical energy conversion. During such a conversion, both the high activity and the stability of catalysts were critical. We prepared an Au-supported C3N4 catalyst—i.e., Au/C3N4-500(N2)—by strongly anchoring Au nanoparticles (~5 nm) onto a C3N4 matrix—which simultaneously enhanced the activity towards the photosynthesis of H2O2 and the stability when it was reused. The yield of H2O2 reached 1320 μmol L−1 on Au/C3N4-500(N2) after 4 h of light irradiation in an acidic solution (pH 3), which was higher than that (1067 μmol L−1) of the control sample Au/C3N4-500(Air) and 2.3 times higher than that of the pristine C3N4. Particularly, the catalyst Au/C3N4-500(N2) retained a much higher stability. The yield of H2O2 had a marginal decrease on the spent catalyst—i.e., 98% yield was kept. In comparison, only 70% yield was obtained from the spent control catalyst. The robust anchoring of Au onto C3N4 improved their interaction, which remarkably decreased the Au leaching when it was used and avoided the aggregation and aging of Au particles. Minimal Au leaching was detected on the spent catalyst. The kinetic analyses indicated that the highest formation rate of H2O2 was achieved on the Au/C3N4-500(N2) catalyst. The decomposition tests and kinetic behaviors of H2O2 were also carried out. These findings suggested that the formation rate of H2O2 could be a determining factor for efficient production of H2O2.
Highlights
Hydrogen peroxide (H2 O2 )—a mild and environment-friendly oxidant—has been used as a green chemical and applied in a variety of industrial and living activities—such as papermaking, water treatment, chemical synthesis, disinfection, and sterilization [1]
The smaller-sized Au possessed more edges, corners, and steps, which were favorable for the adsorption of reactive species and further catalytic reactions
The Au nanoparticles were strongly anchored onto the C3 N4 matrix by a carbon-layer-stabilized method
Summary
Hydrogen peroxide (H2 O2 )—a mild and environment-friendly oxidant—has been used as a green chemical and applied in a variety of industrial and living activities—such as papermaking, water treatment, chemical synthesis, disinfection, and sterilization [1]. The process involves light capture on the photocatalyst, charge separation under light irradiation, charge transfer to the surface of the photocatalyst, water/alcohol oxidation by photo-generated holes, and the reduction of dioxygen by photo-generated electrons [9,10,11] In such a process, a highly efficient photocatalyst could be a core factor in order to direct the synthesis of H2 O2. The g-C3 N4 exhibited enhanced activity when combined with mixed-metal oxide (MMO) [26] The reason for this is that the positive shift of the conduction band of C3 N4 improved the two-electron reduction of dioxygen to H2 O2. The kinetics were studied in order to understand the determining pathway for H2 O2 production
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