Investigation of the parameters influencing the durability of gas diffusion electrodes for CO2 reduction

Abstract

The increasing temperature of the Earth due to anthropogenic greenhouse gas emissions, specifically CO2, has led to a massive increase in research focusing on mitigating the greenhouse emissions to comply with the Paris Agreement. Strategies such as direct air carbon capture have been thoroughly investigated however, new methods of CO2 utilisation need to be developed to maximize effectiveness and minimize the financial cost of implementing industrial scale CO2 removal and utilisation. This research investigates using bismuth nanoparticles (BiNPs) prepared via PLAL on GDEs for CO2 reduction. It was shown that BiNPs are effective and selective towards CO2 reduction under standard conditions as well as when using artificial seawater as an electrolyte. However, demonstrating the effectiveness of the catalyst was not the main goal of this research, instead an investigation of the factors influencing long-term electrode and catalyst durability was performed. It was shown different electrolyte compositions affected both the activity and durability of the BiNPs, also it was shown that various changes to the feed-gas composition affected the activity and durability of the catalyst and electrode. From this it was found that electrolytes with a Cl- presence showed much higher rates of degradation, and that any change to feed-gas composition led to drastic decreases in activity and durability. Most notably an O2 presence decreased activity significantly. In parallel to these tests, an on-line EC-MS was employed to characterize the products being made and showed BiNPs will reduce NO3 and NO2 present in the electrolyte. It was also investigated how sulfur-doping the catalyst might influence its activity and selectivity. Various compositions were tested and it was found that up to 2.5wt% S resulted in a lowering of the overpotential for CO2 reduction and gave much higher FE and PCD than seen in BiNPs by themselves.