Climate change is among the greatest challenges for humankind in the 21st century. Carbon Capture and Utilisation (CCU) allows the production of value-added chemicals from CO2, reducing at the same time the undesirable effects of global warming. Among the available methods for CO2 utilisation, the electrochemical reduction appears as a promising technological solution to store intermittent renewable energy in the form of chemical bonds, leading to valuable chemicals such as formic acid, methanol or methane, which can be put back into the market. The application of electrochemical membrane reactors (ecMRs) for the valorisation of CO2 allows the separation of the catholyte and anolyte compartments, leading to an enhanced separation of reaction products and avoiding their re-oxidation. Among these membrane-based reactors, the utilisation of Membrane Electrode Assemblies (MEAs), where the cathode and anode are coupled with a conductive membrane, are gaining importance. Besides, gas diffusion electrodes (GDEs) are able to reduce mass transfer limitations and therefore, enhance efficiencies in the process of CO2 electroreduction. Thus, the aim of the present review is to compile the literature on the application of membrane reactors for CO2 electroreduction, paying special attention to the type of membrane, reactor configuration and catalytic material in electrochemical reactors. Then, a performance comparison in terms of Faradaic efficiency for different products reported to date, is carried out.The authors gratefully acknowledge the financial support of the Spanish Ministry of Economy and Competitiveness (MINECO) through the project CTQ2013-48280-C3-1-R. Ivan Merino-Garcia and Jonathan Albo would like also to thank the MINECO for the Early Stage Researcher grant (BES2014-070081) and Juan de la Cierva postdoctoral program (JCI-2012-12073)

Copper-based surfaces appear as the most active catalysts for CO ₂ electroreduction to hydrocarbons, even though formation rates and efficiencies still need to be improved. The aim of the present work is to evaluate the continuous gas-phase CO ₂ electroreduction to hydrocarbons (i.e. ethylene and methane) at copper nanoparticulated-based surfaces, paying attention to particle size influence (ranging from 25–80 nm) on reaction productivity, selectivity, and Faraday efficiency (FE) for CO ₂ conversion. The effect of the current density and the presence of a microporous layer within the working electrode are then evaluated. Copper-based gas diffusion electrodes are prepared by airbrushing the catalytic ink onto carbon supports, which are then coupled to a cation exchange membrane (Nafion) in a membrane electrode assembly. The results show that the use of smaller copper nanoparticles (25 nm) leads to a higher ethylene production (1148 μ mol m ⁻² s ⁻¹ ) with a remarkable high FE (92.8%), at the same time, diminishing the competitive hydrogen evolution reaction in terms of FE. This work demonstrates the importance of nanoparticle size on reaction selectivity, which may be of help to design enhanced electrocatalytic materials for CO ₂ valorization to hydrocarbons.