Cobalt-Doped Carbon Gels as Electro-Catalysts for the Reduction of CO2 to Hydrocarbons

Abstract

Two original series of carbon gels doped with different cobalt loadings and well-developed mesoporosity, aerogels and xerogels, have been prepared, exhaustively characterized, and tested as cathodes for the electro-catalytic reduction of CO 2 to hydrocarbons at atmospheric pressure. Commercial cobalt and graphite sheets have also been tested as cathodes for comparison. All of the doped carbon gels catalyzed the formation of hydrocarbons, at least from type C1 to C4. The catalytic activity depends mainly on the metal loading, nevertheless, the adsorption of a part of the products in the porous structure of the carbon gel cannot be ruled out. Apparent faradaic efficiencies calculated with these developed materials were better that those obtained with a commercial cobalt sheet as a cathode, especially considering the much lower amount of cobalt contained in the Co-doped carbon gels. The cobalt-carbon phases formed in these types of doped carbon gels improve the selectivity to C3-C4 hydrocarbons formation, obtaining even more C3 hydrocarbons than CH 4 in some cases.

Metal-Carbon-CNF Composites Obtained by Catalytic Pyrolysis of Urban Plastic Residues as Electro-Catalysts for the Reduction of CO2

“…Therefore, the current findings demonstrate that all composites work as electro-catalysts in this reaction and that they are able to produce the CO 2 transformation to at least C4 hydrocarbons. Moreover, the composite PCo exhibits high selectivity to C3 products (Figure 7) within this group of detected products, which is in accordance with a recent finding with another type of Co doped carbon materials [22]. On the other hand, although PNi is mainly selective to CH 4 , the amount of C3 produced was also higher than C2.…”

“…On the other side, we can see that the rate of hydrocarbon formation tends to decrease after~100 min of reaction for PNi and PFe, and somewhat later for PCo. This type of catalytic behavior has been previously observed [22] and explained by a high formation of H 2 and O 2 , which can provoke a dilution effect of the hydrocarbon formation in the gas phase of the reactor [32]. In any case, the following catalytic tendency can clearly be observed: PCo > PNi > PFe, which is in accordance with the apparent faradaic efficiencies calculated at 95 min of reaction time (Table 4).…”

“…It is important to clarify that that only the detected hydrocarbons (nor H 2 neither O 2 formation) have been included in the faradaic efficiencies calculations. Faradaic efficiencies of this order have been previously obtained with Fe and Co doped carbon gels [22,23]. Therefore, the current findings demonstrate that all composites work as electro-catalysts in this reaction and that they are able to produce the CO 2 transformation to at least C4 hydrocarbons.…”

“…Although this CO 2 reduction mechanism is still being studied [20], the products obtained in the direct electrochemical reduction of CO 2 to hydrocarbons can achieve several carbon atoms [21]. Regarding the hydrocarbon selectivity, recently [22,23], a high selectivity to C3-hydrocarbons among the detected products has been reported using Co-and Fe-carbon electrodes. Moreover, Fe-carbon electrodes have shown a well-fitted linear correlation between the average crystal sizes of iron and the faradaic efficiencies: the smaller the crystal size, the higher the faradaic efficiency [23].…”

Progress toward Commercial Application of Electrochemical Carbon Dioxide Reduction

“…Catalyst placement within carbon layers can have a substantial impact on GDE performance. 128 These GDEs are typically produced by airbrushing inks containing a catalyst nanopowder and ionomer dispersion onto a carbon-based diffusion layer, 147 electrodeposition onto carbon paper, 148 incorporation into carbon-diffusive materials, 149 or roll-out methods using carbon pastes on metal mesh, 107 although in many cases leakage of the catholyte through the GDE is a hurdle for continuous operation. 150 The key advantage of these room-temperature electrolyzers that use a gaseous CO 2 feed is their capability to sustain high current density, durability, product separability, and energy efficiency, all of which are key quantitative metrics for benchmarking.…”