Heterogeneous Cu(I)‐SBA‐15 Mediated Catalytic Reduction of Substituted Nitroarenes

Tunable Metal-Free Imidazole-Benzimidazole Electrocatalysts for Oxygen Reduction in Aqueous Solutions

A series of metal-free imidazole-benzimidazole catalysts (ImBenz-H, ImBenz-NO2 , ImBenz-OCH3 ) for oxygen reduction reaction (ORR) were prepared. We demonstrate that the electrocatalytic O2 reduction by ImBenz-NO2 with the electron-withdrawing group showed high selectivity toward H2 O with the number of electrons transferred (n=3.7) in a neutral aqueous solution. The highest ORR selectivity toward H2 O2 was achieved using ImBenz-H (n=2.4) in an alkaline solution. Electrochemical studies of reaction kinetics disclosed that the highest turnover frequencies were obtained from ImBenz-H in both neutral and alkaline aqueous solutions. The results prove that the ORR selectivity is tunable by modulating the substituent of the ImBenz catalysts. Furthermore, DFT calculations suggested that the ORR mechanism of ImBenz-H involves the electron transfer from imidazole-benzimidazole to O2 resulting in the formation of H2 O2 which supports the redox active properties of the catalysts ImBenz.

Continuous Synthesis of Uniformly Dispersed Mesoporous SBA-15 Supported Silver Nanoparticles in a Coiled Flow Inverter Reactor

Mesoporous silica supported nanocatalysts have shown great potential in industrial processes due to their unique properties, such as high surface area, large pore volume, good chemomechanical stability and so on. Controllable and tunable synthesis of supported nanocatalysts is a crucial problem. Continuous synthesis of supported nanoparticles has been reported to get uniformly dispersed nanomaterials. Here, a method for continuous synthesis of uniformly dispersed mesoporous SBA-15 supported silver nanoparticles in a coiled flow inverter (CFI) microreactor is described. Compared to Ag/SBA-15 synthesized in the conventional batch reactor and Ag synthesized in continuous flow, mesoporous silica nanocatalysts synthesized in continuous flow are found to have smaller average size (7-11 nm) and narrower size distribution. The addition of capping agents can effectively change the characteristic of catalysts. Moreover, two kinds of support with different surface area and pore size have been added into the continuous synthesis. This method can provide further understandings for the synthesis of uniformly dispersed supported nanocatalysts in continuous flow, especially for mesoporous nanomaterials, which provides the possibilities of large-scale yield process of supported nanocatalysts in industry.