The Preparation And Research Of Electrocatalysis Properties For Silver Nanocatalysts

Silver nanocatalysts have been widely used in ethylene epoxidation reaction, carbon monoxide oxidation, oxygen reduction reaction (ORR), hydrogen peroxide reduction and so on. The catalytic activity of silver nanocatalysts has a lot to do with size, dispersion of Ag nanoparticles and chemical environment around them. So that is a very important to research the influence on the catalytic activity from size of the Ag nanoparticles and the chemical environment around them. In this paper, we mainly research the influence on electrocatalytic H2O2reduction from size effect of Ag nanoparticles in the first part. In a second part of the study, cathode oxygen reduction reaction and reaction mechanism from synergistic effect which exsited between Ag nanoparticles and highly decentralized CoOx nanoparticles were researched further. The details of the work are listed as follows:In this work, we synthesized extra-small size Ag/SiO2nanocatalysts and calcined them at different atmosphere (N2, Air, N2H4/N2, H2O/N2and CH3OH/N2) to regulate the size of Ag nanoparticles. Subsequently, we studied the size effect of Ag nanoparticles for electrocatalytic H2O2reduction. The results showed:different calcination atmosphere made some significant differences for the size of Ag nanoparticles. And corresponding Ag/SiO2nanocatalysts were very different for response to H2O2.Secondly, binary CoOx-Ag/reduced graphene oxide nanocomposites (CoOx-Ag/rGO) were synthesized through a one-pot solvothermal method. And its ORR activity was tested under0.1mol/L KOH alkaline solution. The corresponding characterization and test results showed that CoOx nanoparticles could greatly promote dispersion of anchored Ag nanoparticles, decrease the size of Ag nanoparticles and increase the limiting current density for the whole CoOx-Ag/rGO nanocomposites when catalyzing oxygen reduction reaction (ORR) in alkaline medium. Compared with pure Ag/rGO and CoOx/rGO nanocatalysts, a much higher current density and a preferable four-electron pathway were achieved for the CoOx-Ag/rGO nanocomposites with the interaction of CoOx and Ag nanoparticles. Meanwhile, the CoOx-Ag/rGO nanocomposites showed remarkable long-term stability and tolerance toward methanol than the commercially available20%Pt/C catalyst. More importantly, this work could finally lead to a practical significance for developing high-performance bicomponent electrocatalysts with low-cost for fuel cells and relevant electrochemical technologies. In addition, we developed a multistep method for synthesizing Co-Ag/N-GO nanocomposites doped with sulfur elements. And the related ORR activity was carried out under alkaline medium. The results showed that the catalysts had excellent ORR activity.