Electrochemical engineering of the anode reaction for energy efficient CO2RR.

Global warming is one of the biggest challenges that our society is facing today. True circularity of carbon is needed to fulfil the increasing demand for energy while reducing greenhouse gas emissions. The electrochemical reduction of CO₂ back to valuable molecules for chemical industry or as e-fuels are examples of how the carbon cycle can be restored. At imec we are using nanotechnology to improve the efficiency of electrochemical reactions in electrolyzers and fuel cells. We have developed a few micron thick nanomesh electrode with extremely large surface area which significantly lowers the reaction overpotential, making the electrocatalytic reaction more energy efficient [1]. The nanomesh electrode is currently being upscaled for applications in hydrogen electrolyzers [2]. Today, we are further developing this technology towards CO₂ electroreduction to products like forming gas and methanol. We are developing gas-diffusion-electrodes (GDE) with high throughput and a potential to convert CO2 directly from the waste of flue gas and eventually even from the air. We are developing smart catalyst approaches to steer the electrocatalytic reaction path towards the desired products and yields. We are working on sorbent materials to augment CO2 supply to the catalyst in the gas diffusion electrodes. We are using modeling to understand the mass transport and confinement effects in these nanoporous gas electrodes. All these efforts will lead to significant improvements in the cathode reaction. However, the reaction efficiency is determined by the cell potential and thus also by the anode reaction, which is too often ignored. In this PhD topic, we will engineer the anode reaction for an efficient cell reaction. The electrochemical reduction of CO2 is usually done from bicarbonate solutions with pH between 6 and 8. Loss of CO2 by chemical conversion to carbonate because of the local alkaline environment at the cathode is an issue. At the anode, the local environment becomes acid, releasing CO2 from the carbonate compounds. However, forming of a local alkaline and local acidic environment at the cathode and anode, respectively, introduces a voltage difference and thus lowers the efficiency. In this pH, the concept of electrolyte composition will be reassessed from the bottom-up using electrochemical analysis and modeling. Suitable electrolytes and membranes will be developed with the final goal of building a CO₂-electrolyzer with high CO2 conversion efficiency.

[1] https://www.imec-int.com/en/press/100-fold-current-density-enhancement-puts-imecs-nanomesh-electrodes-pole-position-high

[2] https://www.imec-int.com/en/press/flemish-expertise-centres-join-forces-industry-push-green-hydrogen-production-forward

[3] https://www.imec-int.com/en/articles/novel-nanomaterial-promises-improvements-in-batteries-and-many-more-sustainable-applications