In this work, we investigate the catalytic properties of silver nanoparticles supported on silica spheres. The technique to support silver particles on silica spheres effectively avoids flocculation of nanosized colloidal metal particles during a catalytic process in the solution, which allows one to carry out the successful catalytic reduction of dyes. The effects of electrolytes and surfactants on the catalytic properties of silver particles on silica have been investigated. It is found that the presence of surfactants depresses the catalytic activity of the silver particles to some extent by inhibiting the adsorption of reactants onto the surface of the particles. Electrolytes either increase the migration rate of reactants in the solution resulting in an increase in the catalytic reaction rate or inhibit the adsorption of reactants onto the surface of the silver particles leading to a loss in the activity of the metal particles.

Co3O4-coated N- and B-doped graphene hollow spheres synthesized by a simple and scalable method have been used as electrocatalysts for the ORR and the OER, demonstrating higher electrochemical performance and better durability than commercial Pt/C and RuO2/C, respectively.

Development of inexpensive, efficient, and stable nonprecious-metal-based bifunctional catalysts for oxygen reduction (ORR) and evolution (OER) reactions remains an enormous challenge. This work reports on an excellent bifunctional electrocatalyst consisting of ultrathin N-doped carbon (1–3 graphitic carbon layers) coated Fe1.2Co nanoparticles and N-doped carbon nanotubes (Fe1.2Co@NC/NCNTs). The Fe1.2Co@NC/NCNTs have an extremely low Fe/Co content (6.7 wt %), but with highly efficient and durable bifunctionality for ORR and OER. Specifically, the Fe1.2Co@NC/NCNT exhibits onset potential (E onset = 0.842 V vs RHE) and half-wave potential (E 1/2 = 0.82 V vs RHE) for ORR and onset potential of 1.43 V vs RHE and overpotential of 355 mV at 10 mA cm–2 for OER. The potential gap (ΔE) between E 1/2 of ORR and E OER at 10 mA cm–2 (E j=10) for the Fe1.2Co@NC/NCNTs is 0.765 V, which surpasses the commercial Pt/C and Ir/C catalysts and most state-of-the-art bifunctional catalysts previously reported. Most notably, when used in the Zn-air battery, the Fe1.2Co@NC/NCNT exhibits superior efficiency and durability to the Pt–Ir/C catalysts. This strongly suggests that the Fe1.2Co@NC/NCNT can be used as an efficient bifunctional catalyst with potential applications in the field of clean electrochemical energy storage and conversion technologies.