Title : Coupling of cuo@nibiox catalyzed glycerol oxidation to carbon dioxide reduction reaction for enhanced energy efficiency
Abstract:
With the growing awareness of the severity of the global energy crisis and the environmental damage caused by extensive use of fossil fuels, together with a high carbon intensity of manufacturing, there is a strong push towards sustainable development1. Among the promising solutions, biofuels derived from animal fats and vegetable oils have emerged as a viable alternative2. Along with the increase in biofuel production, glycerol is generated as a byproduct of biodiesel production, constituting ~10 wt%3. Therefore, converting glycerol into a high-value product would generate value, remove an undesired component, and reduce the total cost of biofuels) and the possible generation of high-added value products, GEOR is a promising anodic alternative to the typical OER, and drive up energy efficiency and profitability of an electrolytic process5. However, GEOR faces several criticalities. Indeed, the glycerol electrooxidation mechanism is complex, with multiple intermediates and branched reaction pathways that can lead to a scattered product distribution6. Also, deep GEOR can even result in complete oxidation and thus CO2 emission. Therefore, developing a catalyst that preferentially promotes GEOR over OER while also achieving selectivity towards a specific added-value product represents an open challenge.
In this study, we designed a non-noble metal-based electrocatalyst (CuO@NiBiOx, CNBO) for selective and efficient GEOR. The CNBO-catalyst demonstrated high selectivity and achieved nearly 100% GEOR Faradaic efficiency (FE), 90% of which is conveyed into FA. Bismuth incorporation was found to be crucial as it modified the structure of the mixed oxide, increasing the surface concentration of Ni(III) species and thus enhancing the catalytic activity for GEOR. In-situ studies confirmed the formation of NiOOH, which is identified as the active site for GEOR and suggests an indirect GEOR mechanism. This study demonstrates the potential of GEOR to replace OER in Carbon dioxide reduction reaction (CO2RR) electrolyzers. Depending on the nature of the CO2RR catalyst (Ag or Sn), we could obtain either an easy-to-separate mixture of high-added value products (CO and FA) or a single product (FA) with FEFA > 85% at both electrodes. Moreover, we demonstrate that replacing OER with GEOR in a CO2RR-electrolyzer can save up to 25% of the energy used for electrolysis while the co-production of FA at both electrodes can halve the energy per mole required for its electrosynthesis.
