Enhancing C 2+ product selectivity in CO 2 electroreduction by enriching intermediates over carbon-based nanoreactors.

Electrochemical CO 2 reduction reaction (CO 2 RR) to multicarbon (C 2+ ) products faces challenges of unsatisfactory selectivity and stability. Guided by finite element method (FEM) simulation, a nanoreactor with cavity structure can facilitate C-C coupling by enriching *CO intermediates, thus enhancing the selectivity of C 2+ products. We designed a stable carbon-based nanoreactor with cavity structure and Cu active sites. The unique geometric structure endows the carbon-based nanoreactor with a remarkable C 2+ product faradaic efficiency (80.5%) and C 2+ -to-C 1 selectivity (8.1) during the CO 2 electroreduction. Furthermore, it shows that the carbon shell could efficiently stabilize and highly disperse the Cu active sites for above 20 hours of testing. A remarkable C 2+ partial current density of-323 mA cm -2 was also achieved in a flow cell device. In situ Raman spectra and density functional theory (DFT) calculation studies validated that the *CO atop intermediates are concentrated in the nanoreactor, which reduces the free energy of C-C coupling. This work unveiled a simple catalyst design strategy that would be applied to improve C 2+ product selectivity and stability by rationalizing the geometric structures and components of catalysts.