Deposition of Cu on CNT to synthesize electrocatalysts for the electrochemical reduction of CO2: Advantages of supercritical fluid deposition technique

Abstract

One of the most promising technologies for the mitigation of CO2 emissions involves its electrocatalytic reduction to valuable products. However, the development of effective catalysts is still a challenge. In this work, three different techniques have been compared for the synthesis of catalysts involving Cu-based nanoparticles deposited on carbon nanotubes (Cu/CNT): precipitation, microemulsion and supercritical fluid deposition (SFD). According to XRD, SFD allows obtaining mainly copper nanoparticles, while copper oxides are obtained by precipitation. Crystallite size of predominant Cu species of catalysts are between 7 (microemulsion) and 16 nm (SFD). The use of these catalysts in the electrochemical reduction of CO2 in gas phase produce carbon monoxide as main CO2 reduction product, followed by formic acid and methane. The catalyst obtained by microemulsion exhibited poor reproducibility. The catalyst synthesized by SFD achieved the largest CO2 conversion rate, a 30 % higher than that obtained with the one synthesized by precipitation.