Effect of Sn and Ru in Pt-Based Catalysts for Alcohol Oxidation in Alkaline Media: A Combined Electrochemical and DFT Study

Pt-Sn/C and Pt-Ru/C electrocatalysts were synthesized by a polyol method at nominal atomic ratios of 1:1, 2:1, and 3:1, and evaluated for the ethanol oxidation reaction (EOR) and ethylene glycol oxidation reaction (EGOR) in alkaline media. EDS confirmed compositions close to the nominal values, XRD evidenced fcc Pt-M alloy formation, and ADF-STEM revealed well-dispersed nanoparticles below 3 nm. Cyclic voltammetry showed that both Sn and Ru enhance activity relative to Pt/C: Pt-Sn1:1 delivered the highest forward current density in the Sn series (1486 mA mg−1Pt for EOR; 2583 mA mg−1Pt for EGOR), whereas Pt-Ru shifted the onset to more negative potentials (down to −539 mV vs. SHE for EOR), with Pt-Ru3:1 reaching 1858 (EOR) and 2434 mA mg−1Pt (EGOR). Chronoamperometry revealed higher current retention during EGOR than EOR for all catalysts, indicating fewer poisoning intermediates from ethylene glycol. DFT calculations of CO adsorption on 1:1 and 3:1 model surfaces rationalize the distinct roles of the two metals: Sn excludes CO from Sn sites at both compositions and weakens the Pt-CO bond by 0.602 eV at 1:1, while Ru weakens it moderately yet binds CO strongly at both compositions; the bifunctional supply of OHads by Ru, inferred from the more negative onset potentials, accounts for its higher activity. PDOS analysis links these trends to distinct Pt d-band modifications.