Presentation Date: Feb 14, 2026
AGSA Abstract
Electrochemical CO₂ reduction to multi-carbon products on copper catalysts offers sustainable chemical manufacturing pathways, yet poor selectivity limits practical application. This work systematically investigates how electronic structure modification and reaction environment optimization enable selective formation of ethylene, ethanol, and acetate. Copper-based electrocatalysts with controlled dopant incorporation (phosphorus, tin, selenium) were synthesized and characterized to establish electronic structure-selectivity relationships. X-ray photoelectron spectroscopy and density functional theory calculations revealed copper partial positive charge varying from +0.13 to +0.47 depending on dopant electronegativity. These materials demonstrated distinct selectivity: phosphorus-doped copper favored ethylene (43% Faradaic efficiency), tin-doped copper produced ethanol (48.5%), and copper selenide yielded acetate (40%) at 350 mA cm⁻² with stable operation exceeding 220 hours. A unified mechanistic framework proposes all products originate from a common acetyl intermediate, where copper charge state determines pathway preference. Comprehensive electrolyte optimization across pH 4–14 revealed weakly acidic conditions (pH 6) achieved exceptional ethylene selectivity of 73% at 300 mA cm⁻² with 51% single-pass CO₂ conversion over 400 hours. Mechanistic analysis established that pH controls surface carbon monoxide coverage: sparse coverage at pH 6 directs chemistry toward ethylene while dense coverage under alkaline conditions promotes ethanol. Marcus theory modeling explained that phosphate buffers provide optimal balance between CO₂ activation and hydrogen suppression. Systematic cation investigation demonstrated larger ions (cesium) suppress hydrogen evolution from 31% to 4%, while increasing potassium concentration from 0.1 to 2 M enhanced ethylene selectivity from 42% to 65% through interfacial electric field effects and pH buffering. This integrated approach establishes comprehensive design principles: tailored copper electronic structure provides intrinsic selectivity control, optimized pH balances competing reactions, and appropriate cation selection enhances performance through interfacial effects.
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