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Selective electrochemical conversion of CO2 to HCOOH is obtained at the surface of a carbon-supported bimetallic cathode material composed of copper and palladium nanoparticles. Polycrystalline copper or large copper particles are well-known to catalyze CO2 reduction to hydrocarbons at relatively negative potentials, or when their surface is covered by copper oxides (Cu2O and CuO). Cu-based materials modified by various palladium contents (0< × <100), were synthesized by using the microwave-assisted polyol method to serve as a cathode in the selective CO2-into-HCOOH transformation. Herein, we developed a targeted preparation route toward the metal content/catalytic activity relationship correlating atomic ratio with faradaic efficiency (FE) to formate formation (ca. 60% FE) at - 0.72 V vs. RHE, which represents a 703 mV overpotential at pH=7. Consequently, the occurrence of this reduction reaction slows down the parallel H2 production from the solvent consumption, while the neighboring Cu- Pd provides excellent activity and a good efficiency toward CO2 reduction via the hydridation of the CO2 molecule to orientate the reaction to formate rather than carbon monoxide or H2 evolution. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is the oldest studied and most challenging of the electrochemical reactions. Due to its sluggish kinetics, ORR became the major contemporary technological hurdle for electrochemists, as it hampers the commercialization of fuel cell (FC) technologies. Downsizing the metal particles to nanoscale introduces unexpected fundamental modifications compared to the corresponding bulk state. To address these fundamental issues, various synthetic routes have been developed in order to provide more versatile carbon-supported low platinum catalysts. Consequently, the approach of using nanocatalysts may overcome the drawbacks encountered in massive materials for energy conversion. This review paper aims at summarizing the recent important advances in carbon-supported metal nanoparticles preparation from colloidal methods (microemulsion, polyol, impregnation, Bromide Anion Exchange...) as cathode material in low temperature FCs. Special attention is devoted to the correlation of the structure of the nanoparticles and their catalytic properties. The influence of the synthesis method on the electrochemical properties of the resulting catalysts is also discussed. Emphasis on analyzing data from theoretical models to address the intrinsic and specific electrocatalytic properties, depending on the synthetic method, is incorporated throughout. The synthesis process-nanomaterials structure-catalytic activity relationships highlighted herein, provide ample new rational, convenient and straightforward strategies and guidelines toward more effective nanomaterials design for energy conversion. [ABSTRACT FROM AUTHOR]

Copper-supported mesoporous carbon nanocatalysts (Cu/FDU-15) were synthesized using an easy and convenient one-pot soft-template method for low-overvoltage CO 2 electroreduction. TEM imaging revealed the presence of large Cu nanoparticles (diameter 140 nm) with Cu 2 O nanoparticles (16 nm) as an additional phase. From the electron tomography observations, we found that the copper particles were placed inside and on the exterior surface of the porous FDU-15 support, providing an accessible surface for electrocatalytic reactions. CO 2 electrolyses showed that the mesostructured Cu/FDU-15-350 cathode materials were active towards CO 2 conversion to formic acid with 22 % Faradaic efficiency at a remarkably low overpotential of 290 mV, hydrogen being the only side-product. The catalyst's activity correlates to the calculated metallic surface area, as determined from a geometrical model, confirming that the mesoporous channels act as a diffusion path for the CO 2 molecule, and that the whole Cu surface is accessible to CO 2 , even if particles are entrapped in the carbon matrix., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)