Various strategies have been proposed to date in order to mitigate the concentration of CO₂ in the atmosphere, such as the separation, storage, and utilization of this gas_. Among the available technologies, the electrochemical valorisation of CO₂ appears to be an innovative technology, in which electrical energy is supplied to establish a potential between two electrodes, allowing CO₂ to be transformed into value-added chemicals under mild conditions. It provides a method to recycle CO₂ (in a carbon neutral cycle) and, at the same time, a way to chemically store the excess of renewable energy from intermittent sources, thus reducing our dependence on fossil fuels. Among the useful products that can be obtained, methanol is particularly interesting as a platform chemical, and it has gained renewed and growing attention in the research community. Accomplishments to date in the electroreduction of CO₂ to methanol have been encouraging, although substantial advances are still needed for it to become a profitable technology able to shift society to renewable energy sources. This review presents a unified discussion of the significant work that has been published in the field of electrocatalytic reduction of CO₂ to methanol. It emphasizes the aspects related to process design at different levels: cathode materials, reaction media, design of electrochemical cells, as well as working conditions. It then extends the discussion to the important conclusions from different electrocatalytic routes, and recommendations for future directions to develop a catalytic system that will convert CO₂ to methanol at high process efficiencies.

Gas-diffusion electrodes are prepared with commercial Cu2O and Cu2O–ZnO mixtures deposited onto carbon papers and evaluated for the continuous CO2 gas phase electroreduction in a filter-press electrochemical cell. The process mainly produced methanol, as well as small quantities of ethanol and n-propanol. The analysis includes the evaluation of key variables with effect in the electroreduction process: current density (j = 10–40 mA cm−2), electrolyte flow/area ratio (Qe/A = 1–3 ml min−1 cm−2) and CO2 gas flow/area ratio (Qg/A = 10–40 ml min−1 cm−2), using a 0.5 M KHCO3 aqueous solution.\ud The maximum CO2 conversion efficiency to liquid-phase products was 54.8% and 31.4% for Cu2O and Cu2O/ZnO-based electrodes at an applied potential of −1.39 and −1.16 V vs. Ag/AgCl, respectively. Besides, the Cu2O/ZnO electrodes are expected to catalyze the CO2 electroreduction for over 20 h. These results may provide new insights into the application of gas diffusion electrodes to alleviate mass transfer limitations in electrochemical systems for the transformation of CO2 to alcohols.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness (MINECO), under the projects CTQ2013-48280-C3-1-R, CTQ2014-55716- REDT and Juan de la Cierva program (JCI-2012-12073)

Magnetic ionic liquids are room temperature ionic liquids, which have paramagnetic properties by themselves without the need of adding magnetic particles.