Cu4sn/C As Electrocatalyst for Selective Electrochemical Reduction of CO2 to CO: Investigation V
ia on-Line Mass Spectrometry and in-Line Gas Chromatograph
Authors: Camilo Mariana Romano , Silva Wanderson Oliveira , de Lima Fabio Henrique Barros 
Published: February 2020

Different strategies for the global climate change and the carbon dioxide (CO2) emission reduction are being the goal of many researches in recent year. The application of new technologies for direct utilization of CO2 conversion could be interesting options to recycling the molecule. The electrochemical reduction for the conversion of CO2 into added-value carbon-based products as useful fuels has been studied and it involves a new source of sustainable energy. Among the different investigated electrocatalysts, Cu is distinctive for generating hydrocarbons, mainly methane (CH4) and ethylene (C2H4) [1,2], but suffer from deactivation and low faradaic efficiency (FE). Herein, it was investigated the behavior of carbon-supported Sn-modified copper alloy nanoparticles (Cu4Sn/C) for the carbon dioxide electroreduction, and the reaction products were monitored by on-line Differential Electrochemical Mass Spectrometry (DEMS) measurements. The faradaic and ionic currents for m/z = 2 (H2) and 28 (CO), obtained during DEMS experiments of cyclic voltammetry for Cu4Sn/C, in CO2-saturated 0.1 mol L-
1 KHCO3 electrolyte, at room temperature, showed that the CO/H2 ratio for Cu4Sn/C is lower than that for Au/C (included for comparison - known as an efficient electrocatalyst for CO generation), but higher when compared to that for Sn/C (which is known to produce CO and HCOO- ion in parallel to H2 [3]) and Cu/C (for copper, the m/z = 28 has contribution from methane and ethylene fragments). Stability tests, performed via chronoamperometric curves, showed that the CO signal for Au/C decreased within few minutes, with the concomitant increase of the H2 formation, evidencing deactivation during the CO2 electroreduction. This is probably due to accumulation of adsorbed CO-like intermediates [4]. On the other hand, and interesting, the CO signal for Cu4Sn/C alloy nanoparticles remained stable. Long-term stability test, however, are still necessary to address this important aspect. Quantitative analyses obtained by using in-line gas chromatography have shown FE for CO production of 23 and 13 % for Au/C and Cu4Sn/C, respectively. Therefore, the results obtained herein revealed that CO can be produced by using the non-noble metal-based Cu4Sn/C electrocatalyst. Although this material presented lower faradaic efficiency than that for Au/C, the electrochemical and DEMS measurements demonstrated higher stability for CO generation during the electrochemical polarization.

Acknowledgements

The authors thank FAPESP (2014/26699-3, 2013/16930-7 and 2016/13323-0) and CNPq for financial support.

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