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ABSTRACT.The voltammetric profile of preferentially shaped platinum nanoparticles has been used to analyze of the different sites present on the surface. This analysis has been made, for the first time, in NaOH solutions and revisited in sulfuric and perchloric acid media. The comparison with the voltammetric profiles of the model surfaces, i.e., single crystal electrodes, allows assigning the different signals appearing in the voltammograms of the nanoparticle to specific sites on the surface. A good correlation between the shape of the nanoparticle determined by TEM and the voltammetric profile is obtained. For the nanoparticles characterized in alkaline media, the adsorbed species on the surface has been characterized and three major regions can be identified. Below 0.2 V, the major contribution is due to hydrogen adsorption whereas above 0.6 V, adsorbed OH is the main species on the surface. In between both values, the signals are due to competitive adsorption/desorption process of OH/H. New criteria for determining the active area in NaOH solutions has been proposed. In this medium, the total charge density measured between 0.06 and 0.90V stands for 390 µC cm 2 have been characterized, the behavior of the nanoparticles towards CO oxidation has been analyzed.It has been found that the nanoparticle edges are key sites in the oxidation of CO.

Production of multicarbon products (C 2+ )from CO 2 electroreduction reaction (CO 2 RR) is highly desirable for storing renewable energy and reducing carbon emission. The electrochemical synthesis of CO 2 RR catalysts that are highly selective for C 2+ products via electrolyte-driven nanostructuring is presented. Nanostructured Cu catalysts synthesized in the presence of specific anions selectively convert CO 2 into ethylene and multicarbon alcohols in aqueous 0.1m KHCO 3 solution, with the iodine-modified catalyst displaying the highest Faradaic efficiency of 80 %a nd ap artial geometric current density of ca. 31.2 mA cm À2 for C 2+ products at À0.9 V vs.RHE. Operando X-rayabsorption spectroscopyand quasi in situ X-rayp hotoelectron spectroscopym easurements revealed that the high C 2+ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by the synthesis,p resence of subsurface oxygen and Cu + species,and the adsorbed halides.

Convoluted selectivity trends and a missing link between reaction product distribution and catalyst properties hinder practical applications of the electrochemical CO2 reduction reaction (CO2RR) for multicarbon product generation. Here we employ operando X-ray absorption and X-ray diffraction methods with subsecond time resolution to unveil the surprising complexity of catalysts exposed to dynamic reaction conditions. We show that by using a pulsed reaction protocol consisting of alternating working and oxidizing potential periods that dynamically perturb catalysts derived from Cu2O nanocubes, one can decouple the effect of the ensemble of coexisting copper species on the product distribution. In particular, an optimized dynamic balance between oxidized and reduced copper surface species achieved within a narrow range of cathodic and anodic pulse durations resulted in a twofold increase in ethanol production compared with static CO2RR conditions. This work thus prepares the ground for steering catalyst selectivity through dynamically controlled structural and chemical transformations.