Negative Emissions based on Photoelectrochemical Methods: Surface Investigation of Potential Catalysts

Mitigating climate change is one of the greatest challenges humanity has to face in the next decades. For this purpose, negative emissions – the active removal of large amounts of carbon dioxide from the atmosphere (~10Gt/a) – are indispensable, meaning that highly efficient methods for carbon dioxide removal have to be developed.1In our work we aim to design a photoelectrochemical system that uses solar energy to drive a catalytic process that converts carbon dioxide into long term stable storage products such as oxalate or carbon flakes. Here, we present first results of electrochemical and spectroscopic investigations on two promising catalytic processes for carbon dioxide conversion which are based on metallic cerium and a GaInSn–based liquid metal alloy. The determination of the conversion efficiency allows for an estimation of the area demand of a large-scale deployment of our artificial photosynthesis-based process to meet the carbon dioxide reduction goals.Apart from developing catalytic processes that result in high solar to carbon efficiencies, our work aims to improve the knowledge on the solid/liquid interface between catalyst and electrolyte. This is done by applying a combination of well established electrochemical methods like Cyclic Voltammetry or Chronoamperometry and operando Spectroscopy based on Raman and Reflection Anisotropy Spectroscopy. This is expected to allow for monitoring and controlling changes at the catalytic surfaces, like the formation of potentially catalyst poisoning species such as cerium fluoride. Since surface processes play a crucial role in the carbon dioxide conversion, understanding and controlling them might pave the way for improvements on the conversion efficiency. This would further reduce the area requirements of our system, which in turn would ease the suspected land-use conflict potential caused by climate change mitigation measures.