Abstract
Pt2RuMo/C catalysts were synthesized by the modified polyol method in the presence and absence of Li(C2H5)3BH (LBH), annealed at 600 °C under H2 atmosphere to improve the reduction of Pt and Ru to provide stronger interactions between Mo and another metals. LBH affected the physico-chemical characteristics of Pt2RuMo, that is, in the presence of LBH an increment of Mo(IV) amount and a decrease in the PtRu alloying degree were observed. The catalytic activity for hydrogen oxidation in the presence and absence of CO (CO tolerance) of the Pt2RuMo/C catalysts as anodes in polymer electrolyte membrane fuel cells (PEMFCs) was compared to that of a commercial PtRu/C catalyst. The results indicated that the CO tolerance increased with an increase in Mo(IV) content, but the stability increased with an increment of the amount of Ru oxides in the catalysts.
Highlights
Polymer electrolyte membrane fuel cells (PEMFCs) are viable devices for energy conversion due to their high power density, efficiency, and low operation temperatures
The carbon monoxide (CO) adsorption on Pt is stabilized by two simultaneous effects, due to the hybridization of the band states: electron transfer from the CO filled 5σ molecular orbital to the dσ band of Pt; back-donation of electrons from metal dπ orbital to empty 2π* anti-bonding orbital of CO, resulting in the formation of adsorbed CO (COads ), which competes with H for Pt active sites [3]
[31] by an electronic effect: electron transfer from Mo to Pt causes a lowering of the Pt 5d vacancies the addition of Mo to PtRu does not significantly affect the PEMFC performance, but in the presence and a downshift of the 5d-center promotes the reduction of CO binding energy
Summary
Polymer electrolyte membrane fuel cells (PEMFCs) are viable devices for energy conversion due to their high power density, efficiency, and low operation temperatures. To explain why alloying weakens both the COads internal and C-Pt bonds and reduces the COads adsorption energy This model correlates (1) Mulliken population, (2) density-of-states analysis of the COads orbitals, (3) the individual interaction of these orbitals with the metal lattice bands, and (4) their polarizations within the COads molecule. CO tolerance than PtRu catalysts, in particular at higher fuel utilization conditions, ascribed to the higher activity of Pt/MoOx due to the water-gas shift (WGS) reaction and CO electro-oxidation [14,15,16,17] Their stability for long times of operation in PEMFCs, was not evaluated.
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