Simple synthesis of Pt-Ag/SnO2-C for use as a catalyst of methanol oxidation in alkaline media

Abstract

Pt-Ag/SnO2-C is a highly active electrocatalyst for the methanol oxidation reaction (MOR) in alkaline media at different methanol concentrations. Pt-Ag alloy with a loading of 10 wt% metal on SnO2-C was synthesized via ultrasound in the absence of any special capping agent or thermal treatment to reduce costs. The catalyst was characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning (SEM) and transmission (TEM) electron microscopy to investigate its morphology and structure. The electrochemical performance of the catalyst was evaluated using cyclic voltammetry (CV), CO adsorption, and chronoamperometry (CA). The results obtained for the Pt-Ag/SnO2-C synthesized as described above were compared with those obtained for Pt-Ag/C and Pt/C synthesized via ultrasound and tested under the same conditions. The crystalline structure of the platinum and the formation of the Pt-Ag alloy was explored using XRD. According to the microscopy results, the Pt-Ag alloy tended to agglomerate on the substrates considered here (C and SnO2-C) and thus showed poor dispersion compared to Pt nanoparticles. The catalytic activity of Pt in the MOR was improved by adding silver to obtain a Pt-Ag alloy; results showed a twofold increase in catalytic activity with this alloy, which was due to the synergistic effect of the Pt–Ag electronic interaction in the alloy. Furthermore, the incorporation of SnO2 into the carbon substrate to form a Pt-Ag/SnO2-C composite led to enhanced catalytic activity compared to Pt-Ag/C because of the bifunctional effect of SnO2-C.