(517d) Investigation of the Main Factor That Drives Selectivity on Rough Cu-Based Catalysts for CO2 Electroreduction

Carbon dioxide (CO₂) is the residual gas of combustion, agricultural and industrial processes and is associated with global warming. There is great potential for sustainable use of this waste gaseous byproduct towards useful chemicals and low carbon fuels (methane, ethylene) with the utilization of electroreduction and renewable electricity as the energy source. The selection of the electrocatalyst is of paramount importance for CO₂ electroreduction since it is related with hindrances like selectivity, current efficiency, and stability¹that still limit its broader application.

Recent studies^2-4 have presented the importance of catalyst surface morphology and showed that rough copper (Cu) catalysts can improve selectivity and Faradaic efficiency towards hydrocarbon production. Understanding and controlling the main factor that influences selectivity on such surfaces would lead to the improvement of catalystsâ?? design towards the desired chemicals or fuels. This report examines the main factor that drives the selectivity on rough Cu-based catalysts surfaces. For that purpose, Cu-based catalysts were synthesized by the use of electrodeposition on copper substrates. Roughness was controlled through electrodeposition parameters of charge passed and potential applied. The evaluation of each catalyst involved the examination of surface morphology, the efficiency during the CO₂ reduction, and product selectivity. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and capacitance measurements with cyclic voltammetry were used. The products analysis was conducted with a micro gas chromatograph (microGC) for gas products. Results showed a relation between roughness and product selectivity. Higher roughness was associated with the higher formation of ethylene (C₂H₄) whereas lower roughness catalysts form as main hydrocarbon product methane (CH₄).

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(2) Tang, W.; Peterson, A. A.; Varela, A. S.; Jovanov, Z. P.; Bech, L.; Durand, W. J.; Dahl, S.; Norskov, J. K.; Chorkendorff, I. The importance of surface morphology in controlling the selectivity of polycrystalline copper for CO₂ electroreduction. Physical Chemistry Chemical Physics 2012, 14(1), 76.

(3) Qiao, J.; Jiang, P.; Liu, J.; Zhang, J. Formation of Cu nanostructured electrode surfaces by an annealingâ??electroreduction procedure to achieve high-efficiency CO₂ electroreduction. Electrochemistry Communications 2014, 38(0), 8.

(4) Kas, R.; Kortlever, R.; Milbrat, A.; Koper, M. T. M.; Mul, G.; Baltrusaitis, J. Electrochemical CO₂ reduction on Cu₂O-derived copper nanoparticles: controlling the catalytic selectivity of hydrocarbons. Physical Chemistry Chemical Physics 2014, 16 (24), 12194.