Oxygen Electroreduction on PtCo₃, PtCo and Pt₃Co Alloy Nanoparticles for Alkaline and Acidic PEM Fuel Cells

Abstract

Pt-Co alloy nanoparticles have emerged as one of the most promising electrocatalysts for the oxygen reduction reaction (ORR) in hydrogen fuel cells. Our study presents a comprehensive structural, compositional and electrochemical characterization linked with ORR activity for carbon supported PtCo 3 , PtCo, and Pt 3 Co alloy nanoparticle catalysts in 0.1 M HClO 4 and 0.1 M KOH. Surface-sensitive cyclic voltammetry was used to investigate the changes of composition of outermost atomic layers of Pt-Co alloys. Our electrochemical results in alkaline media clearly show the stability and voltage-induced accumulation of Co on the particle surface, whereas in 0.1 M HClO 4 the voltage cycling initiates the rapid dissolution of Co to form a Pt-enriched surface surrounding by alloy core. We correlated the ECSA and ORR activity with the as-synthesized chemical composition of Pt-Co alloys. In results, after electrochemical treatment in 0.1 M HClO 4 the Pt mass based activities (j mass ) increase according: Pt(HT) < PtCo < Pt 3 Co < PtCo 3 at comparable particle size. Unlike to acid, after voltage cycling in 0.1 M KOH j mass increase according: PtCo 3 < Pt(HT) < PtCo < Pt 3 Co. However, in 0.1 M KOH activated PtCo 3 core-shell catalyst shows 4-5 fold higher mass activity compared to pure Pt and Pt(HT).

Investigation of oxygen reduction in alkaline media on electrocatalysts prepared by the mechanical alloying of Pt, Co, and Ni

“…This reduction was previously reported in a study of the particle size and alloying effects on Pt-based alloy catalysts, and a relationship between the specific activity and both the Pt surface area and the Pt-Pt bond distance was found [60]. In Table 3, the data of particle size and activity for Pt alloys in alkaline media reported elsewhere and this study are shown [16,31,42,61]. The mass activity for Pt-Co reported in Table 3 is 13.78 mA mg -1 comparing this value with the Pt-black used for PEM fuel cells as 100 at.%; the former has a 77 % of performance.…”

“…The different conditions, preparation method, particle size, composition, and catalyst loading make rather difficult a comparison; however, for PtCo prepared in this study and considering those parameters, it can be concluded that its performance is in between of Refs. [16,31,42].…”

Gold-promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

“…The ORR activity is also affected by the pH and leads to different mechanism in acid and alkaline media 49 . In acidic media, nanoparticle size effect has an important role in increasing the electrochemical surface area, thus increasing the catalytic activity, but in alkaline media, only negligible changes were due to nanoparticle size effects 50,51 .…”

Carbon-Supported Pt-Based Alloy Electrocatalysts for the Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells: Particle Size, Shape, and Composition Manipulation and Their Impact to Activity

“…To study the effect of composition on catalytic activity, Strasser's group used an impregnation method to prepare a series of high-surface-area carbon-supported Pt− Co alloy nanoparticle catalysts with atomic ratios of 1:3, 1:1, and 3:1. 175 After electrochemical treatment in 0.1 M HClO 4 , the Pt-based mass activities increased 5-fold from Pt/C to Pt 1 Co 3 /C in the order of Pt/C < Pt 1 Co 1 /C < Pt 3 Co 1 /C < Pt 1 Co 3 /C, with similar particle sizes of 3−4 nm. Using electrochemical dealloying, Strasser's group also studied a series of PtM 3 /C systems with different metals as the second alloy elements (M = Cu, Co, and Ni).…”