Significant role of surface activation on Pd enriched Pt nano catalysts in promoting the electrode kinetics of ethanol oxidation: Temperature effect, product analysis & theoretical computations

The present investigation involves the electrode kinetic studies on ethanol electro-oxidation in alkaline medium within the temperature range 20–80 °C on carbon supported platinum and platinum–palladium alloys of different compositions obtained through NaBH4 reduction of the respective precursor salts. The experimental work was further substantiated by computational work based on DFT calculations. Different textural properties of the catalyst matrix were determined by the application of BET equation to the adsorption isotherms. Surface morphology, structure and composition of the catalyst matrices were revealed through XPS, XRD, TEM and EDAX analyses. Electro-analytical techniques were deployed to derive the kinetic parameters along with the activation energies for the oxidation reactions, studied over the mentioned range of the temperature. Further attempt was made to estimate the intermediates formed during the course of the reaction by the help of ion exchange chromatography. The incorporation of Pd into Pt matrix was found to decrease the charge transfer resistance and activation energy of the ethanol oxidation, enabling faster reaction kinetics and better conversion of the fuel into the end products, presumably by alleviating the problem of CO poisoning which remains as one of the critical issues with bare Pt catalyst. The investigation finally include the density functional theory computations on some Pt–Pd mixed cluster configurations along with pure Pt and Pd to realize the effect of local electronic structures and geometry on the relative catalytic activity of the alloyed and single metal particles. It was predicted that the highest activity of the alloyed catalyst Pt30Pd70/C is due to the optimal presence of Pt & Pd in the matrix, rendering the surface activation by OH– and favorable charge distribution among the Pt and Pd sites leading to improved CO oxidation within the fuel cell potential range.