High Throughput Thin Film Pt-M Alloys for Fuel Electrooxidation: Low Concentrations of M (M = Sn, Ta, W, Mo, Ru, Fe, In, Pd, Hf, Zn, Zr, Nb, Sc, Ni, Ti, V, Cr, Rh)

Abstract

Eighteen Pt-M binary (M = Sn, Ta, W, Mo, Ru, Fe, In, Pd, Hf, Zn, Zr, Nb, Sc, Ni, Ti, V, Cr, Rh) thin film composition spreads were deposited at low M concentrations using magnetron sputtering and screened for methanol and ethanol electrooxidation activity using a fluorescence assay. Characterization of these thin films was performed using high energy X-ray diffraction and X-ray fluorescence. The electrochemical fluorescence assay revealed highest activity in the films with M = Sn, Zn, In, Fe, and Ru. Pt-M (M = Sn, Zn, In) showed highest activity at concentrations below 5 atom-% with a high fraction of Pt fcc(111) texturing and Pt-Fe showing the best activity at 10 atom-% Fe. On the other hand, the best (most negative) fluorescence onset potential in the Pt-Ru system was observed at a concentration of 35 atom-% Ru with only slight texturing of the film. To explore the potential origins of the observed catalytic activity, preliminary calculations on the d-band center shift with alloying were performed for bulk concentrations of up to 30 atom-% for Fe and 16 atom-% for M = Sn, Zn.