Tailored Pt-Sn based catalyst for direct methanol fuel cells – A computational research

Pt is the best catalyst for fuel cells, Never the less, the cost of Pt and its poisoning by CO in the ppm level prevents their commercialization market. Very thin layers of Pt and PtSn alloys supported on metallic Sn is suggested as catalyst for fuel cells. This approach may provide high utilization of Pt - catalysis and removal of adsorbed CO from Pt surface via a well-known Pt-Sn bi-functionality mechanism^1,2 as well.

The effect of various numbers of layers of Pt or PtSn alloy supported on a well-defined core of Sn was studied. The adsorption energy of CO and MeOH was studied in comparison to the adsorption energy of CO and MeOH over pure Pt.

The calculations have been carried out using the Vienna Ab initio Simulation Program (VASP) using periodic boundaries, PAW PBE pseudopotentials and cutoff energy of 400 eV was used. According to the computational result, the adsorption energy of CO over a very thin layer of Pt supported on tin is reduced (less negative, less favored) while methanol is still adsorbed. The same effect, reducing the adsorption energy of CO while methanol is still adsorbed, was demonstrated on an alloy of PtSn, and an alloy of PtSn supported on tin as well.

These results indicate that Pt-Sn based catalyst are expected to be an improved catalyst for Direct Methanol Fuel Cells.

Reference

(1) Wang, K.; Gasteiger, H. a.; Markovic, N. M.; Ross, P. N. On the Reaction Pathway for Methanol and Carbon Monoxide Electrooxidation on Pt-Sn Alloy versus Pt-Ru Alloy Surfaces. Electrochim. Acta 1996, 41 (16), 2587–2593.

(2) Mukerjee, S.; Urian, R. C. Bifunctionality in Pt Alloy Nanocluster Electrocatalysts for Enhanced Methanol Oxidation and CO Tolerance in PEM Fuel Cells: Electrochemical and in Situ Synchrotron Spectroscopy. Electrochim. Acta 2002, 47 (19), 3219–3231.