Graphene-Supported Silver Nanoparticles for pH-Neutral Electrocatalytic Oxygen Reduction

Developing an electrocatalyst with desired activity and affordable cost for oxygen reduction reaction (ORR) of microbial fuel cell (MFC) remains a key challenge for practical application of MFC in wastewater treatment. In order to find an economic replacement of Pt-based catalysts while maintaining comparable catalytic efficiency, an electrocatalyst of graphene-supported silver nanoparticles (AgNPs/rGO) was prepared via a facile coreduction and its activity toward ORR in pH-neutral MFC was examined. It has been demonstrated that one-pot aqueous coreduction yielded high-quality AgNPs/rGO catalyst, as revealed by X-ray diffraction and transmission electron microscope. Interestingly, the XPS profiles also indicated the presence of oxygen-containing groups on graphene surface, which provided nuclei to form AgNPs. The resultant AgNPs/rGO catalyst displayed good ORR catalytic activity under pH-neutral condition in cyclic voltammogram and its selectivity of four-electron reduction was verified by rotating disk electrode (RDE) measurement. Moreover, AgNPs/rGO could deliver power generation and sustainability comparable to those of commercial Pt/C in a double-chamber MFC. Thus, we have demonstrated, for the first time, that graphene sheets may provide an alternative way for preparation of Ag nanocomposite catalyst and AgNPs when loaded onto graphene surface can function as a promising replacement of Pt-based catalysts under pH-neutral condition. Since Ag is less expensive and more resistant to poisons than Pt, AgNPs/rGO has better potential to be applied to MFC for recovering energy during wastewater treatment.