Synergistic spatial confinement and microenvironment regulation by Pd-doped Cu₂O/ pyridine-functionalized V₂C MXene...

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 (j_total) 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.