Synergistic spatial confinement and microenvironment regulation by Pd-doped Cu2O/ pyridine-functionalized V2C MXene for efficient CO2 electroreduction to ethylene.

Electrochemical conversion of CO2 to multi‑carbon (C2) products is constrained by sluggish carbon‑carbon bond formation reactions and linear scaling relationships between intermediate binding energies. Herein, we report a dual-level microenvironment engineering strategy to overcome these bottlenecks by integrating tandem catalysis within a spatially confined and electronically modulated architecture. Specifically, Pd-doped Cu2O hollow nanospheres were assembled onto pyridine (Py) functionalized V2C MXene (V2C-Py@Cu2O-Pd). In this hierarchical design, the hollow nanoreactors confine the intermediates, elevating the local *CO concentration generated by the Pd tandem sites. Meanwhile, the highly conductive V2C-Py scaffold improves charge transport and stabilizes the hybrid interface via Py anchoring, collectively regulating the interfacial electron microenvironment. The optimized catalyst delivered a C2 product faradaic efficiency (FE) of 79.7% ± 2.5% in an H-cell and, in a flow cell, achieved total current density (jtotal) of 477.2 ± 13.5 mA cm-2 with an ethylene FE of 48.2% ± 3.2%. In situ Raman spectroscopy and density functional theory (DFT) calculations reveal that an increased proportion of restricted rotation (P1) versus stretched adsorption (P2) CO species corresponds to higher *CO coverage, lowering the energy barrier for formation of crucial intermediates and facilitating CC coupling. These findings demonstrate that combining micro-environmental regulation with tandem catalysis is an effective strategy for improving selective CO2-to-C2 conversion.