Tuning the crystallinity of Cu-based electrocatalysts: Synthesis, structure, and activity towards the CO2 reduction reaction

• Cu-based nanomaterials with tuneable crystallinity tested for CO2RR. • The role of the structural properties on the catalysts’ activity were investigated. • The improved catalytic performances of crystalline system over the amorphous are explained. • Combined experimental-computational approach to understand catalytic activity. The rising levels of CO 2 have spurred growing concerns for our environment, and curbing CO 2 emissions may not be practically viable with the expanding human population. One attractive strategy is the electrochemical CO 2 reduction (CO 2 RR) into value added chemicals but because of the chemical inertness of the CO 2 molecule, the electrochemical reduction requires a suitable catalyst. Cu-based catalysts have been largely investigated for CO 2 RR, however, the difficulty achieving a high selectivity and faradaic efficiency towards specific products, especially hydrocarbons, is still a challenge, alongside the concern over cost, stability and scarcity of the metal catalyst. The present research focuses on tuning the crystallinity of Cu nanoparticles via a green, cost-friendly, and facile method, called the urea glass route. Remarkably, the incorporation of a selected nitrogen-carbon rich source (namely, 4,5 dicyanoimidazole) at low temperatures allow the formation of an oxidized derived amorphous Cu system, whilst a second thermal treatment enables the transformation to crystalline Cu 0 . We found that the combination of surface Cu 0 and Cu 1+ (observed via XPS studies) present in our amorphous and crystalline Cu nanoparticles leads to interesting differences in the final catalytic activity when tested under CO 2 reaction conditions. The combination of extended X-ray absorption fine structure (EXAFS) experiments and molecular dynamics simulations provides compelling evidence for the amorphous and metallic nature of Cu nanoparticles.