Experimental and density functional theory studies on PtPb/C bimetallic electrocatalysts for methanol electrooxidation reaction in alkaline media

Chemical-Dealloying-Derived PtPdPb-Based Multimetallic Nanoparticles: Dimethyl Ether Electrocatalysis and Fuel Cell Application

In this work, we report a novel multimetallic nanoparticle catalyst composed of Pt, Pd, and Pb and its electrochemical activity toward dimethyl ether (DME) oxidation in liquid electrolyte and polymer electrolyte fuel cells. Chemical dealloying of the catalyst with the lowest platinum-group metal (PGM) content, Pt2PdPb2/C, was conducted using HNO3 to tune the catalyst activity. Comprehensive characterization of the chemical-dealloying-derived catalyst nanoparticles unambiguously showed that the acid treatment removed 50% Pb from the nanoparticles with an insignificant effect on the PGM metals and led to the formation of smaller-sized nanoparticles. Electrochemical studies showed that Pb dissolution led to structural changes in the original catalysts. Chemical-dealloying-derived catalyst nanoparticles made of multiple phases (Pt, Pt3Pb, PtPb) provided one of the highest PGM-normalized power densities of 118 mW mgPGM-1 in a single direct DME fuel cell operated at low anode catalyst loading (1 mgPGM cm-2) at 70 °C. A possible DME oxidation pathway for these multimetallic catalysts was proposed based on an online mass spectrometry study and the analysis of the reaction products.

Tuning Surface Structure of Pd3Pb/Pt n Pb Nanocrystals for Boosting the Methanol Oxidation Reaction

Developing an efficient Pt-based electrocatalyst with well-defined structures for the methanol oxidation reaction (MOR) is critical, however, still remains a challenge. Here, a one-pot approach is reported for the synthesis of Pd3Pb/Pt n Pb nanocubes with tunable Pt composition varying from 3.50 to 2.37 and 2.07, serving as electrocatalysts toward MOR. Their MOR activities increase in a sequence of Pd3Pb/Pt3.50Pb << Pd3Pb/Pt2.07Pb < Pd3Pb/Pt2.37Pb, which are substantially higher than that of commercial Pt/C. Specifically, Pd3Pb/Pt2.37Pb electrocatalysts achieve the highest specific (13.68 mA cm-2) and mass (8.40 A mgPt -1) activities, which are ≈8.8 and 6.8 times higher than those of commercial Pt/C, respectively. Structure characterizations show that Pd3Pb/Pt2.37Pb and Pd3Pb/Pt2.07Pb are dominated by hexagonal-structured PtPb intermetallic phase on the surface, while the surface of Pd3Pb/Pt3.50Pb is mainly composed of face-centered cubic (fcc)-structured Pt x Pb phase. As such, hexagonal-structured PtPb phase is much more active than the fcc-structured Pt x Pb one toward MOR. This demonstration is supported by density functional theory calculations, where the hexagonal-structured PtPb phase shows the lowest adsorption energy of CO. The decrease in CO adsorption energy and structural stability also endows Pd3Pb/Pt n Pb electrocatalysts with superior durability relative to commercial Pt/C.

One-step synthesis of ultrathin PtxPb nerve-like nanowires as robust catalysts for enhanced methanol electrooxidation

Ultrathin Pt_xPb nerve-like nanowires (NNWs) with a diameter of only around 3.6 nm were synthesized by a one-step wet-chemical strategy, and they served as robust catalysts for greatly enhancing methanol electrooxidation both under acidic and alkaline conditions. Due to the high CO-poisoning tolerance, superior electrocatalytic activity and stability endowed by the Pt-Pb alloyed composition and the unique structure, the Pt_3.5Pb NNWs showed the highest specific activity of 2.78 mA cm^-2 in acidic media and 6.51 mA cm^-2 in alkaline media toward the methanol oxidation reaction (MOR), which are 5.24 and 4.12 times higher than those of the commercial Pt/C catalysts, respectively. Meanwhile, the demonstrated synthetic strategy for Pt-Pb nanocrystals may stimulate more inspiration and strategies of the novel metal-based nanocrystals for promising applications in electrocatalysis.

An efficient and durable novel catalyst support with superior electron-donating properties and fuel diffusivity for a direct methanol fuel cell

The direct methanol fuel cell (DMFC) is projected as one of the most promising next-generation fuel cell technologies and reducing the catalyst loading at the anode side with an improvement in the sluggishness of methanol oxidation has become the key research topic in the field.