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

Abstract

Keggin-structured phosphotungstic acid H 3 PW 12 O 40 (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. Graphical AbstractPhosphotungstic 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.

Polyoxometalates (POMs): from electroactive clusters to energy materials

“…More recently, a PW 12 -modified Ag@Pt/MWCNT electrocatalyst was prepared by electrostatic interaction with positively charged chitosan-functionalized core-shell Ag@Pt NPs on MWCNTs. 261 The results showed that PW 12 improves the electrocatalytic activity of Ag@Pt NPs; with a E 1/2 (half-wave electrode potential) for the ORR which positively shifted 44 mV from that of Ag@Pt NPs/MWCNTs, and a mass activity (I m ) and specific area activity (I s ) about 2 times higher than those of Ag@Pt NPs/MWCNTs. The enhanced activity can be explained by the protective effect of the PW 12 layer on the catalyst surface.…”

Highly Active PdNi/RGO/Polyoxometalate Nanocomposite Electrocatalyst for Alcohol Oxidation

“…For instance, a variety of supporting materials including foam silica, multiwalled carbon nanotubes (MWNTs), and indium tin oxide (ITO) have been utilized to support the nanocatalysts. However, reduced graphene oxide (RGO) has been used as a catalyst support for DAFCs due to the large specific surface area, superior electric conductivity, and high chemical stability. , Recently, heteropolyacids (HPAs) have also been incorporated into the bimetals to improve the catalytic performance. , HPAs are a rapidly increasing class of compounds and have been extensively studied as catalysts, additives, chemical cleaners, and surface promoters, owing to their unique structural and electronic versatility, in which phosphotungstic acid (H 3 PW 12 O 40 , HPW) is one of the most investigated Keggin-type HPAs. A most appealing and notable characteristic of HPW is that they can acquire and release several electrons per molecule without changing the structure. , …”

“…23,24 Recently, heteropolyacids (HPAs) have also been incorporated into the bimetals to improve the catalytic performance. 25,26 HPAs are a rapidly increasing class of compounds and have been extensively studied as catalysts, additives, chemical cleaners, and surface promoters, owing to their unique structural and electronic versatility, 27 HPW is that they can acquire and release several electrons per molecule without changing the structure. 28,29 Herein, phosphotungstic acid and PdNi nanoparticles supported on RGO (PdNi/RGO/HPW) nanomaterials were simply synthesized by a facile chemical method, in which PdNi/ RGO nanomaterials were first synthesized, followed by the subsequent introduction of HPW into the composite in an aqueous solution.…”