CO2 reduction mechanism can reduce the environmental impact of the greenhouse gas and produce valuable energy-storage carbon products, like hydrocarbons and alcohols. This is only possible by a limited number of catalysts, among which Cu is particularly interesting due to its effectivity and low cost.
Some challenges regarding CO2 reduction are high overpotential, low current density and poor catalytic selectivity to desired products. There are many interesting approaches to improve the catalyst design. Carefully designed synthesis of Cu nanoparticles with various size and spacing allows control over selectivity. Here such factors like diffusion of reactants to catalyst surface and readsorption of intermediates play important role.
Cu decorated through-hole carbon nanofibers possess excellent mechanical properties and they can be applied in the reaction directly as cathode, producing almost pure methanol. It is experimentally verified that the catalyst structure is maintained under bending strength, so Cu decorated carbon membranes can be used directly as cathode without any binder and carrier. Among new approaches, Cu-based bimetallic catalysts are also drawing the attention. For example, Sn alloying can greatly enhance catalytic selectivity of Cu surface. Cu-Sn core-shell structure used for conversion of CO2 to CO has high selectivity and can effectively suppress hydrogen formation. Hydrogen adsorption is favored by the local threefold symmetry at Cu edges, but the symmetry is successfully destroyed by Sn substitution. At the same time, charge transfer from Sn to Cu atom compensates for the change, causing less effect on CO adsorption.