Study of Gas Diffusion Electrodes Stability during the Electrochemical CO2 Reduction in Aqueous and Aprotic Electrolytes

Extreme weather events will likely become more frequent or intense with human-induced climate change. The temperature rises and devastating floods are just some of the environmental disasters recorded in recent years. According to the scientific community, the cause to blame is the global warming phenomenon, a problem that arises in response to the accumulation of greenhouse gases in the atmosphere. These can create a mantle that blocks solar radiation from escaping the Earth's surface and modifies the stability of the atmosphere. Carbon dioxide (CO2) produced by human activities is the largest contributor to global warming. It is an extremely stable molecule whose concentration has increased by about 130 ppm within the last 150 years due to increased industrial emissions. The dependency on fossil fuels, the need to tackle global warming and reduce the CO2 concentration in the atmosphere have led to the development of innovative and pollution-fighting technologies. The electrochemical CO2 reduction (EC CO2R) represents one of the most promising options. In this regard, carbon can be reused to synthesise added-value products, e.g. Syngas, and introduced into a circular economy loop, thus reducing both CO2 emissions and the dependence on external energy suppliers This thesis work aims to optimise the performance of the electrochemical CO2 conversion to syngas by identifying the optimum conditions for the stability of the prepared Gas Diffusion Electrode (GDE). Herein, the EC CO2R has been carried out employing ionic liquids (ILs)-based electrolytes, which were previously studied in the research group for CO2 capture by adsorption. To the best of our knowledge, this study is the first to investigate those solutions within a continuous-flow electrochemical cell with copper and silver-based-GDE as cathodes. Different issues were evidenced during the electrochemical tests, such as the carbon-based substrate degradation, colour changes of ILs-electrolyte and the suppression of carbon monoxide (CO) production. Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS) techniques were used to characterise the after-testing samples and understand the behaviour of the system. It was possible to demonstrate that using the FTO-coated Ti-mesh a constant CO production was reached at different applied current densities, achieving a H 2/CO ratio close to 2, which is a suitable feedstock for further methanol synthesis.