Molecular-Level Engineering of Organic-Modified Cu(100) for Tailored Selectivity in CO₂ Electroreduction

Interfacial molecular engineering offers a powerful yet underexplored strategy to modulate the electronic structure and catalytic selectivity of metal-based electrocatalysts. Herein, first-principles calculations reveal how multifunctional organic modifiers, i.e., 2-aminoacetaldehyde and glycine, regulate the electronic properties of Cu(100) and steer reaction pathways during CO₂ electroreduction. Upon adsorption, these molecules form hydrogen bonds with CO₂ through -NH₂ or protonated -NH₃⁺ groups, stabilizing the adsorbed CO₂ intermediate, while simultaneously redistributing the electronic density of the Cu surface, thereby promoting electron transfer to CO₂ and enhancing its activation. The cooperative interaction between -NH₂ and auxiliary groups (-CHO or -COOH) establishes directional hydrogen bond that selectively stabilize key intermediates and lower the C-C coupling barriers. The 2-aminoacetaldehyde further facilitates synergistic dual-site coordination, strengthening interfacial coupling and shifting product selectivity from methane to methanol. Moreover, molecular modification steers distinct C-C coupling pathways: 2-aminoacetaldehyde favors *CHO-*CHO dimerization with ultralow barriers (0.08-0.15 eV), whereas protonated -NH₃⁺ in glycine promotes *CO-*CHO coupling. Concurrently, the competing hydrogen evolution reaction (HER) is effectively suppressed. Overall, this work establishes a unified mechanistic framework linking interfacial configuration to electronic modulation and catalytic selectivity, providing a rational strategy for designing molecularly engineered Cu-based CO₂ electroreduction catalysts.