Towards the electrochemical conversion of carbon dioxide into methanol
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.