Comparative Electrochemical and Spectroscopic Studies of Ethanol Oxidation on Pt(h,k,l) Modified by Osmium Nanoislands

Platinum-Group-Metal High-Entropy-Alloy Nanoparticles

The platinum-group metals (PGMs) are six neighboring elements in the periodic table of the elements. Each PGM can efficiently promote unique reactions, and therefore, alloying PGMs would create ideal catalysts for complex or multistep reactions that involve several reactants and intermediates. Thus, high-entropy-alloy (HEA) nanoparticles (NPs) of all six PGMs (denoted as PGM-HEA) having a great variety of adsorption sites on their surfaces could be ideal candidates to catalyze complex reactions. Here, we report for the first time PGM-HEA and demonstrate that PGM-HEA efficiently promotes the ethanol oxidation reaction (EOR) with complex 12-electron/12-proton transfer processes. PGM-HEA shows 2.5 (3.2), 6.1 (9.7), and 12.8 (3.4) times higher activity than the commercial Pd/C, Pd black and Pt/C catalysts in terms of intrinsic (mass) activity, respectively. Remarkably, it records more than 1.5 times higher mass activity than the most active catalyst to date. Our findings pave the way for promoting complex or multistep reactions that are seldom realized by mono- or bimetallic catalysts.

Effect of the Random Defects Generated on the Surface of Pt(111) on the Electro-oxidation of Ethanol: An Electrochemical Study

In the present work, the Pt(111) surface was disordered by controlling the density of {110}- and {100}-type defects. The cyclic voltammogram (CV) of a disordered surface in acid media consists of three contributions within the hydrogen adsorption/desorption region: one from the well-ordered Pt(111) symmetry and the other two transformed from the {111}-symmetry with contributions of {110}- and {100}-type surface defects. The ethanol oxidation reaction (EOR) was studied on these disordered surfaces. Electrochemical studies were performed in 0.1 M HClO₄ +0.1 M ethanol using cyclic voltammetry and chronoamperometry. Changes in current densities associated to the specific potentials at which each oxidation peak appears suggest that different surface domains of disordered platinum oxidize ethanol independently. Additionally, as the surface-defect density increases, the EOR is catalysed better. This tendency is directly observed from the CV parameters because the onset and peak potentials are shifted to less positive values and accompanied by increases in the oxidation-peak current on disordered surfaces. Similarly, the CO oxidation striping confirmed this same tendency. Chronoamperometric experiments showed two opposite behaviors at short oxidation times (0.1 s). The EOR was quickly catalyzed on the most disordered surface, Pt(111)-16, and was then rapidly deactivated. These results provide fundamental information on the EOR, which contributes to the atomic-level understanding of real catalysts.