Dual-Confinement Structure Design Enables Synergistic Modulation of Local Microenvironment and Electronic Structure for Enhanced CO2 Electroreduction to CO.

Precisely tailoring the local microenvironment and interfacial electronic structure of electrocatalysts is crucial for achieving highly efficient and selective electrochemical CO2 reduction reaction (CO2RR). Herein, we propose a dual-confinement strategy and successfully construct a composite nanoreactor consisting of carbon nanotube (CNT) shells housing nickel nanoparticles encapsulated in nitrogen-doped carbon. In this orchestrated architecture, the CNT serves as a primary confinement framework that effectively enriches OH- ions, creating an alkaline local microenvironment conducive to suppressing the hydrogen evolution reaction and stabilizing intermediates. The internal core-shell units of nitrogen-doped carbon and nickel nanoparticles function as a secondary confinement system, where metal-carbon interactions and controlled N-doping species synergistically optimize the interfacial charge distribution. This configuration enhances the π-p orbital coupling between active sites and CO2 molecules, thereby facilitating CO2 activation and conversion. Benefiting from the dual-confinement effect with the synergistic regulation of the local microenvironment and electronic structure, the catalyst exhibits outstanding catalytic activity and achieves a remarkable CO Faradaic efficiency of 99% at -1.0 V vs. reversible hydrogen electrode. This work demonstrates that the design of multi-level confined structures offers the potential for constructing highly efficient catalysts.