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

Abstract

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.