Magnetic-Field-Assisted CO₂ Electroreduction at Precision-Engineered Ga-Gd Oxide Nanodomain Interfaces

Liquid-metal-derived catalysts offer a unique platform for precision chemistry by enabling structurally adaptive interfaces unconstrained by rigid lattices. Here, we report a magnetically responsive Ga-Gd catalytic system in which ultrafine, surface-localized Gd-rich oxide nanodomains form within a liquid-metal-derived Ga₂O₃ matrix and enable field-sensitive electrochemical CO₂ conversion. Controlled thermal annealing transforms disordered Ga-Gd composites into a defect-suppressed β-Ga₂O₃ framework decorated with nanometric Gd₂O₃ domains, establishing localized electronic and paramagnetic environments without bulk lattice substitution. Atomic-resolution microscopy, XRD, Raman spectroscopy, XPS/UPS, and solid- and liquid-state NMR reveal annealing-induced suppression of defect states, relaxation of surface dipoles, and emergence of localized magnetic interactions at the Ga-Gd-O interface. Under electrochemical CO₂ reduction, annealed Ga-Gd electrodes exhibit pronounced magnetic modulation of activity, with CO₂ conversion increasing from ∼10% at zero field to ∼14-15% under a 200 mT magnetic field (enhancement factor ∼ 1.4-1.5). Product-resolved spectroscopy confirms selective formation of CO (up to ∼0.42 mmol g^-1 h^-1) and CH₃OH (up to ∼0.18 mmol g^-1 h^-1) while excluding hydrocarbon and C-C coupling pathways. The magnetic enhancement is potential-selective and confined to the CO₂ activation window, indicating field-sensitive interfacial kinetics rather than bulk transport effects. These results highlight how ultrafine oxide nanodomains within liquid-metal-derived catalysts can serve as precision-defined, reconfigurable interfacial motifs whose electrochemical reactivity can be dynamically modulated by external magnetic fields, advancing controllable CO₂ conversion within the framework of precision chemistry.