Synthesis and electrocatalytic performance of phosphotungstic acid-modified Ag@Pt/MWCNTs catalysts for oxygen reduction reaction

Keggin-structured phosphotungstic acid H3PW12O40 (HPW)-modified Ag@Pt/MWCNTs electrocatalysts were successfully prepared using a chemical impregnation method. Physical characterization by X-ray powder diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy revealed that the HPW molecules were incorporated into the Ag@Pt/MWCNT structure The diameter of the catalyst used was about 4.0 nm, and electrochemical investigation results indicated that HPW could ameliorate electrocatalytic activity. The catalyst with HPW content of 25 % displayed the best excellent electrocatalytic activity with an electrochemically active area of 83.62 m(2) g(-1) and a half-wave potential for the oxygen reduction reaction of 0.851 V, all ascribed to the high utilization of Pt and the protective effect of the HPW layer on the catalyst surface. The synergic effect of the HPW and Ag@Pt enhanced the rate of electron transfer and increased the catalytic efficiency of oxygen reduction reaction, influencing 4e(-) reduction reactions on Ag@Pt/MWCNTs-HPW catalysts. Phosphotungstic acid-modified Ag@Pt/MWCNTs catalysts were successfully synthesized by the chemical impregnation method. The morphology and catalytic performance of the prepared catalysts were investigated, leading to the understanding of catalytic mechanism of the catalyst in acidic medium, especially, the importance of HPW in the hybrid catalysts. The investigation indicated that the hybrid catalyst showed excellent activity toward oxygen reduction. Schematic diagram for mechanism of ORR on Ag@Pt/MWCNTs-HPW nanostructure.