Development of Cu-based hybrid catalysts for the electrocatalytic CO2 reduction to added value products

Development of Cu-based hybrid catalysts for the electrocatalytic CO2 reduction to added value products. The simultaneous need to reduce greenhouse gas emissions and increase our energy supply makes the electrochemical reduction of CO2 a very attractive alternative. In this context, science seeks effective methods to transform CO2 into chemicals of economic value. Among the possible products to obtain, we are especially interested in species with one or more carbon-carbon bonds, these types of compounds are favored using copper as catalyst. Although some other catalysts can produce this type of bond, none it does with the same efficiency as copper. This thesis is developed in the exposed context, analyzing six catalysts synthesized with different ratios of Cu, Zn and Al2O3 and subsequently exposed to a thermal treatment to obtain C-based oxygenates from CO2. This type of catalyst is traditionally used in thermocatalysis for the efficient production of methanol at high temperature and pressure conditions. Noting the good performance of this catalyst in thermocatalysis, it was chosen to carry out experiment for the electrochemical reduction of CO2 at ambient conditions. In addition, we sought to standardize the synthesis process of the different catalysts, guaranteeing the method's reproducibility. The synthesis was carried out by means of the coprecipitation method by using as precursors the copper, zinc and aluminum nitrates and as a precipitating solution sodium carbonate (1M). As to the operating conditions, the synthesis was performed at neutral pH, the synthesis temperature was 70°C and the calcination temperature was 350°C. The catalysts were characterized through tests of BET, XRD and FESEM. On the other hand, electrochemical tests (CV,LSV,CA) were carried out in the rotating disk electrode (RDE) in order to reduce the mass transfer limitations that may exist due to the low solubility of CO2 in an aqueous medium. The catalyst loading used was 0.6 mg/cm2 and the electrolyte was KHCO3 (0.1M). Among the liquid products obtained are acetone, ethanol, 2-propanol, formate and in some cases, methanol was also obtained. Moreover, gaseous products obtained were hydrogen, carbon monoxide and methane, being these last - gaseous products - those that present the highest faradaic efficiencies. According to these results, we consider that would be interesting to evaluate the performance of the catalysts with another type of cell configuration such as Gas Diffusion Electrode (GDE) cell, thus that faradaic efficiencies of liquid products could be favored with the operating conditions of this configuration.