Facile Synthesis of Bimetallic Pt-Ag/Graphene Composite and Its Electro-Photo-Synergistic Catalytic Properties for Methanol Oxidation

A Pt-Ag/graphene composite (Pt-Ag/GNs) was synthesized by the facile aqueous solution method, in which Ag+ was first transformed into Ag2O under UV light irradiation, and then Ag2O, Pt2+, and graphene oxide (GO) were simultaneously reduced by formic acid. It was found that Pt-Ag bimetallic nanoparticles were highly dispersed on the surface of graphene, and their size distribution was narrow with an average diameter of 3.3 nm. Electrocatalytic properties of the Pt-Ag/GNs composite were investigated by cyclic voltammograms (CVs), chronoamperometry (CA), CO-stripping voltammograms, and electrochemical impedance spectrum (EIS) techniques. It was shown that the Pt-Ag/GNs composite has much higher catalytic activity and stability for the methanol oxidation reaction (MOR) and better tolerance toward CO poisoning when compared with Pt/GNs and the commercially available Johnson Matthey 20% Pt/C catalyst (Pt/C-JM). Furthermore, the Pt-Ag/GNs composite showed efficient electro-photo-synergistic catalysis for MOR under UV or visible light irradiation. Particularly in the presence of UV irradiation, the Pt-Ag/GNs composite exhibited an ultrahigh mass activity of 1842.4 mA·mg−1, nearly 2.0 times higher than that without light irradiation (838.3 mA·mg−1).