SiO2 assisted Cu0–Cu+–NH2 composite interfaces for efficient CO2 electroreduction to C2+ products

The electrochemical CO2 reduction reaction (CO2RR) for high value-added multi-carbon product (C2+) production over copper oxide-based catalysts is an important way to realize the carbon cycle. However, developing effective reaction interfaces and microenvironments to improve the Faraday efficiency (FE) and current density of C2+ remains a major challenge. Herein, we construct Cu0–Cu+–NH2 composite interfaces with the assistance of SiO2. Using Cu2O nanoparticles as a model catalyst, a layer of porous SiO2 is first coated on the surface of the particles, and then, a silane coupling agent containing –NH2 is bonded on the surface of SiO2. The strong interaction between SiO2 and Cu2O at the interface induces the oxidation effect of low valent Cu, and even under the CO2RR, part of Cu+ is reduced to Cu0 and part of Cu+ still maintains positive valence, forming the interface of Cu0–Cu+. SiO2 also acts as a bridge between copper species and –NH2 to create a Cu catalyst–NH2 group interface. With the help of the synergistic effect of the composite interfaces, the optimized Cu2O@SiO2–NH2 catalyst achieves a FE of 81.2% for C2+ products with a current density of 292 mA cm−2 at −1.7 V versus a reversible hydrogen electrode. In situ Raman and attenuate total reflectance-infrared absorption spectroscopy spectra show that the interaction between surface –NH2 and CO2 molecules enhances the adsorption and activation process of CO2 and promotes the formation of CO intermediates (*CO). On the Cu0–Cu+ interface, the C–C coupling process between *CO is accelerated, and the two interfaces synergistically promote the generation of C2+ products. This work provides a new strategy for constructing composite interfaces to improve the CO2RR to C2+ products.