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.

 

References

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