Delocalization state-induced selective bond breaking for efficient methanol electrosynthesis from CO2

Methanol manufacturing by CO2 electrolysis is a potential near-zero-emission route to carbon neutrality, but most of the previous studies in aqueous electrolytes have achieved poor methanol selectivity and yield. Inspired by hard–soft acid–base theory, we proposed that the CO2 electroreduction pathways towards methanol or methane could be switched by tuning the electron delocalization state of Cu catalytic sites. On the basis of this hypothesis, we have designed and synthesized a cuprous cyanamide (Cu2NCN) crystal in which isolated Cu(I) ions strongly conjugated with NCN2− exhibit highly delocalized electrons. Theoretical calculations showed that Cu2NCN substantially reduces the Cu–O interaction of the adsorbed *OCH3 intermediate so that it is weaker than the O–C interaction at the critical reaction bifurcation point of Cu‒*O‒CH3, thus switching the pathway to release *OCH3 and form methanol. The Cu2NCN catalyst exhibits one of the highest recorded CO2-to-CH3OH selectivities (70%) and an outstanding partial current density of −92.3 mA cm−2 in aqueous electrolyte, corresponding to a CH3OH electroproduction rate of 0.160 μmol s−1 cm−2. Despite great progress in electrocatalytic CO2 reduction on Cu-based materials, the selectivity for methanol has remained elusive in contrast to thermocatalytic routes. Here, using Cu2NCN with polarized Cu atoms as the cathode, selectivity of up to 70% for methanol is achieved by favouring cleavage of Cu–O over O–C in the crucial Cu–*O–CH3 intermediate.