Unveiling the Nanoconfinement Effect in CO <sub>2</sub> Electroreduction to CH <sub>4</sub> over Mesoporous Cu-CeO <sub>2</sub> Nanospheres
Lei Xiong, Xianbiao Fu, Wenpu Fan, Jun Zhang, Zixuan Zheng, Lü Shaojie, Dong Wang, Mingze Hao, Qin Yue
Abstract
High Resolution Image Download MS PowerPoint Slide Nanoconfinement provides a promising strategy to promote the electrochemical CO 2 reduction reaction (CO 2 RR) owing to enhanced reactant enrichment and collision. However, the nanoconfinement influence on the CH 4 selectivity from the CO 2 RR with related regulation mechanism is unclear. Herein, a series of mesoporous CeO 2 loaded Cu catalysts with controllable pore size (1.3–5.5 nm) are designed to modulate the CO 2 RR selectivity to CH 4 . It is found that decreasing the pore size can apparently enhance the CO 2 RR performance while inhibiting the HER activity. Moreover, a volcano-type relationship between the CH 4 selectivity and the pore diameter is observed among these catalysts, while Cu-mCeO 2 -3.0 (pore diameter of 3.0 nm) shows the highest CH 4 Faradaic efficiency (66.1 ± 2.9%). The in situ experiments and DFT calculations illustrate that a smaller pore size with stronger confinement over Cu-mCeO 2 - x can promote the adsorption and transformation of reactants (*CO, *CHO, etc.) for CH 4 production, but too narrow confined space (1.3 nm) will contribute to much higher intermediate coverage and promote their collision for C–C coupling to C 2+ products instead, thus reducing the CH 4 selectivity. This work provides designing insights into metal/oxide catalysts with controllable pore size to study the nanoconfinement effect on the CO 2 RR-to-CH 4 activity, which can be extended to other oxide-based catalytic reactions.