CHEMICAL ENGINEERING TRANSACTIONS VOL. 73, 2019 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Andrea D’Anna, Paolo Ciambelli, Carmelo Sunseri Copyright © 2019, AIDIC Servizi S.r.l. I SBN 978-88-95608-70-9; I SSN 2283-9216 Catalytic Activity of Cu and Cu/Sn Electrodes during CO 2 Reduction from Aqueous Media Laura Mais a, *, Simonetta Palmas a , Annalisa Vacca a , Michele Mascia a , Francesca Ferrara b , Alberto Pettinau b a Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, Italy b Sotacarbo S.p.A., c/o Grande Miniera di Serbariu, 09013 Carbonia, Italy l.mais@dimcm.unica.it In this work, we investigated the catalytic activity of copper-based electrodes during CO 2 reduction from KHCO 3 aqueous solutions. Copper electrodes, synthetized by the electrochemical reduction of thermally formed copper oxide (CuRE), or by decorating of CuRE with tin (CuRE/Sn) were tested. Moreover, commercial copper or tin foils have been used for comparison. Different electrochemical techniques such as cyclic voltammeteries and linear sweep voltammetries were adopted in order to derive information on the reductive processes and to characterise the behaviour of the electrodes. Higher cathodic currents were obtained using CuRE and CuRE/Sn with respect to commercial foils. Depending on the applied potential, lower faradic efficiency (FE) is obtained at CuRE/Sn rather than at CuRE, and a very high loading of Sn seems to be required to increase the FE by some percentage points. Interestingly, at the lowest investigated potential (-0.8 V), the presence of Sn, even at low amount, was able to catalyse the formic acid formation, with a FE of 14%. 1. Introduction Carbon dioxide increases continuously in the atmosphere, due to the growth of anthropogenic emissions, and this has made it an issue of global concern, as CO 2 is considered one of the main greenhouse gases responsible for global warming. In recent years, considerable attention has been paid to the control of CO 2 emissions, and their conversion, in order to mitigate the negative impact of this gas on the atmosphere. Currently, the emission of CO 2 into the atmosphere can be reduced by several technologies, such as CO 2 capture and storage (Hossain and De Lasa, 2008). A better approach is to convert carbon dioxide into useful liquid fuels and value-added chemicals, such as formic acid, methanol, methane, etc. (Kortlever et al., 2015). Several techniques have been investigated in recent years, such as photochemistry, thermochemistry and electrochemistry, to reduce catalytically CO 2 to fuels and chemicals (Centi et al., 2013; Lim et al., 2014). Among these, the electrochemical approach has become attractive because it has several advantages, such as easy control and scale-up of the process, mild conditions for the electroreduction of CO 2 . The main drawbacks of the electrochemical reduction of CO 2 under ambient conditions include the very negative potential required and the difficulty in controlling the selectivity of the reaction; in fact, the reduction of CO 2 can occur via 2, 6, 8 and 12 electrons, resulting in a variety of products, such as carbon monoxide, formic acid, methanol, formaldehyde, methane and acetic acid. (Hori et al., 2002; Wang et al., 2015; Chen et al., 2015; Merino-Garcia et al., 2017). Among them, formic acid is one of the most interesting due to its highest value-added with respect to the other possible products from CO 2 reduction. Moreover, formic acid is the simplest naturally existing carboxylic acid, and its demand is dramatically expanding, year by year, due to its various applications. For example, a significant proportion of formic acid is used in agriculture as a preservative, due to its natural antibacterial properties. In industry, formic acid is commonly used in the production of leather, the manufacture of rubber and dyeing of textiles, since, unlike mineral acids, it evaporates without leaving any residues. Furthermore, formic acid has been proposed as a feed for fuel cells (Yu and Pickup, 2008). 97 DOI: 10.3303/CET1973017 Paper Received: 15 March 2018; Revised: 28 August 2018; Accepted: 07 January 2019 Please cite this article as: Mais L., Palmas S., Vacca A., Mascia M., Ferrara F., Pettinau A., 2019, Catalytic Activity of Cu and Cu/sn Electrodes During CO2 Reduction from Aqueous Media , Chemical Engineering Transactions, 73, 97-102 DOI:10.3303/CET1973017