1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 One-Pot Soft-Template Synthesis of Nanostructured Copper-Supported Mesoporous Carbon FDU-15 Electrocatalysts for Efficient CO 2 Reduction Nihat Ege S ¸ ahin, [a] Cle ´ment Comminges,* [a] Anthony Le Valant, [a] Julien Kiener, [b] Julien Parmentier, [b] Teko W. Napporn, [a] Georgian Melinte, [c] Ovidiu Ersen, [c] and Kouakou B. Kokoh* [a] 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. 1. Introduction Energy generation using non-renewable fossil fuels is associ- ated with greenhouse gases emissions, mainly carbon dioxide (CO 2 ), which is the main cause of the global warming. Several studies have been strategically developed in order to valorise the CO 2 molecule, particularly, the processes that take advant- age of the CO 2 reduction reaction (CO 2 RR) in order to produce a variety of useful products including fuels or other derived hydrocarbons. [1] Among the various efficient CO 2 conversion approaches, the electrochemical CO 2 RR route promises a sustainable process for generating liquid fuels such as formic acid (HCOOH), [2] which is an attractive fuel as well as an energetic vector. Especially, it has been used as a fuel in direct formic acid fuel cells (DFAFCs) [3] and as a sustainable chemical for hydrogen storage. [4] The recent developments in DFAFCs revealed that formic acid is one of -promising energy sources for powering portable electronic devices and fuel cell vehicles. The drawbacks on storage capacity and transportation [5] of molecular hydrogen under high pressure are handled by the virtue of production of formic acid as a reversible source of hydrogen storage. Practically, it is more convenient and economic to use hydrogen-containing materials, [6] namely formic acid, which can be broken down under ambient conditions, instead of using highly-pressurized H 2 gas. Hence, it is estimated that global demand of safer and low cost hydro- gen storage materials will dramatically increase for energy- related applications. Thus, there is an increased interest in developing the technological CO 2 -converting devices that improve the Faradaic selectivity in the field of CO 2 electro- reduction to formic acid. To sum up, one of the objectives of this study is to propose an electrochemical approach for the CO 2 -to-HCOOH production that can help to eliminate some obstacles such as hydrogen storage and transportation, and mitigates the dependence of non-renewable fossil fuels. Significant efforts have been made for understanding the electrochemical CO 2 conversion both in homogeneous [7] and heterogeneous catalysis [8] approaches, exposing different reac- tion pathways. [9] Carbon dioxide, as the last oxidation state of carbonaceous organics, is extremely stable and its electro- chemical conversion requires a high overpotential due to its initial reduction to highly energetic bent CO 2 *  radical anion from a single electron transfer. Evidences of the latter adsorbed species were previously revealed by in-situ FTIR spectroscopy [10] and Raman spectroscopy [11] at Pb, Pt and Ag electrode surfaces. Over the past few decades, challenging electrode materials such as metals, [1c,12] metal oxides, [13] and metal-organic com- plexes [14] have been proposed yielding to various CO 2 reduction [a] Dr. N. E. S ¸ahin, Dr. C. Comminges, Dr. A. Le Valant, Dr. T. W. Napporn, Prof. K. B. Kokoh UniversitØ de Poitiers Institut de Chimie des Milieux et MatØriaux de Poitiers (IC2MP-UMR-CNRS 7285) 4 rue Michel Brunet, B27, TSA 51106, 86073 Poitiers cedex 09, France E-mail: clement.comminges@univ-poitiers.fr boniface.kokoh@univ-poitiers.fr [b] Dr. J. Kiener, Dr. J. Parmentier UniversitØ de Haute-Alsace Institut de Science des MatØriaux de Mulhouse, CNRS UMR 7361 15 rue Jean Starcky - BP 2488–68057 cedex, Mulhouse, France [c] Dr. G. Melinte, Prof. O. Ersen UniversitØ de Strasbourg Institut de Physique et Chimie des MatØriaux de Strasbourg (IPCMS), UMR 7504 CNRS 23 rue du Lœss, 67037 cedex 2, Strasbourg, France Supporting information for this article is available on the WWW under https://doi.org/10.1002/cphc.201701352 1371 ChemPhysChem 2018, 19, 1371 – 1381 # 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Articles DOI: 10.1002/cphc.201701352