Studies on the electrochemical reduction of carbon dioxide and nitrite

Abstract

In recent years the topic climate change has been becoming increasingly importantand the need of solutions for decreasing use of fossil fuels and reduction of greenhouse gases such as carbon dioxide in the atmosphere is more and more urgent. The introduction of new technologies in the near future is unavoidable as global warming is proceeding at an unprecedented rate. Renewable energy sources such as solar power or wind power must be made more cost-effective and the storage of the electricity generated must be improved.In this work the electrochemical reduction of carbon dioxide (CO2RR) was investigated as a promising technology for the future that could eectively reduce carbon dioxide (CO2) emissions. Not only can this technique be performed under low-cost ambient conditions but also water and CO2 which are the two precursors are abundant. Furthermore, if a copper-based catalyst is used, C2+ oxygenates, carbohydrates or other carbon compounds can be produced which can be further processed in industry or used as storage for excess renewable electricity from solar and wind power.The first topic in this work was to study the copper nanocubes while providing controlled mass transport conditions with a gas-tight rotation cell where a rotatingcylinder electrode is integrated. This catalyst can produce C2+ products with a highactivity and lower onset potential. However, there is still no explanation where thiseect has its origin. By comparing the experimental results to those obtained byRüscher [1] on polycrystalline copper, it was found that the enhancement is causedby the nanoporous system. A higher pH value prevails in the pores and the residence time of the intermediates is prolonged, which are perfect conditions for C-C coupling. Furthermore, we were able to gain a better understanding of the catalytic mechanism.Secondly, the design of a catalyst that shows the ability to produce urea during thesimultaneous electrochemical reduction of CO2 and NO2- was attempted. Severalcatalysts based on copper or titanium were investigated but no successful result wasachieved and therefore more materials have to be tested in the future. Nevertheless,the copper nanocubes have been shown to also exhibit high selectivity and activityfor the electrochemical reduction of NO2- to ammonia.