One-step electrodeposition of liquid alloys from choline chloride-urea eutectic solvent for CO2 electroreduction

Ga-Sn liquid metal catalysts exhibit high activity in the electrochemical conversion of CO 2 to formic acid. However, achieving high current densities for industrial-scale production is still challenging. A facile one-step electrodeposition method for preparing Ga-Sn thin films on metal foam substrates was proposed. A deep eutectic solvent consisting of choline chloride and urea, which is known as Reline, was used as the electrolyte solvent. The electrochemical behaviors of Sn(II)/Sn(0) and Ga(III)/Ga(0) in Reline were studied on a Pt rotating disk electrode. The diffusion coefficient and exchange current density of Sn(II) and Ga(III) in this electrolyte were determined by the Koutecký-Levich equation. Ga91.6Sn8.4 thin liquid film was electrodeposited on a copper foam substrate and used as the catalytic electrode for electrochemical reduction of CO 2 in a CO 2 -saturated 0.1 M KHCO 3 solution, and a high Faradaic efficiency (90 %) for HCOOH was achieved. Density functional theory (DFT) simulations were conducted to gain deeper insight into the role of the alloy in the CO 2 reduction reaction (CO 2 RR). The results indicate that the incorporation of Sn into the alloy not only introduces additional active sites for *OCHO adsorption but also facilitates the conversion of *COOH intermediates to formate.