Since the industrial revolution the use of fossil fuels has increased exponentially, this increase caused a higher concentration of carbon dioxide in the atmosphere, which is responsible for climate change. To prevent a large-scale change of the earth’s climate humanity needs to switch to renewable energy sources. A large drawback of current renewable energy sources is that they almost all exclusively produce electricity which is hard to store for long periods of time. A possible solution to this energy storage issue is the electrochemical reduction of CO2 with electricity from renewable sources. Catalysts used for this process are transition metals but there are several problems that prevent large-scale implementation. Two fundamental problems with these catalysts are: Low activity causing low reaction rates, and low selectivity causing the formation of undesired products. A possible solution was proposed by Lim et al. (2014)1 where they suggested doping a silver electrode with sulphur to enhance the selectivity and activity for carbon monoxide production. This proposal was put the test in this thesis where silver was doped with sulphur by two different methods and were characterized by different techniques and tested at four different potentials. The method where a sample was immersed in a sulphur containing solution and subsequently annealed proofed to be the most effective way to dope a silver electrode. With the help of gas chromatography it was found out that at lower overpotentials the addition of sulphur is beneficial to its performance to produce CO but at higher potentials this advantage is lost. However if the results of this thesis are compared to literature it is clear that doping with sulphur is not effective. Furthermore it was seen that the sulphur doped Ag electrodes were not very stable and therefore not suited for large-scale implementation.

The worlds energy demand is increasing however, the majority of the energy supply is still based on fossil fuels. The consumption of fossil fuels results in the emission of carbon dioxide which is one of the main greenhouse gases responsible for the ongoing climate change. In order to reduce the carbon dioxide emissions, more and more energy is produced in a re-newable way. Mainly from solar and wind energy. This energy is however intermittent in char-acter and comes in the form of electricity. To overcome the intermittency, the excess pro-duced electricity has to be stored in an efficient reversible way, so that the energy can re-leased again when it is needed. One possible solution that tackles both problems is the elec-trochemical reduction of carbon dioxide in aqueous electrolytes into highly valuable chemicals, or so called solar fuels. In this study, a new infrared spectroelectrochemical cell with an easy exchangeable electrocatalyst is developed to study the reaction mechanism on a silver cata-lyst in 0.1 M KCl and 0.1 M KHCO3 electrolytes at applied potentials of -1.4, -1.6 and -1.8 V vs a Ag/AgCl reference electrode. The performance of the new developed cell is compared to the already proven ATR cell configuration. Investigation of the infrared signal strength showed high infrared signals at angles of incidence of the infrared beam between 30° and 45°. The measured infrared absorption spectra in the thin layer flow cell show three absorption bands which are also present in the obtained infrared absorption spectra of the ATR cell. In the ATR spectra however, three further infrared absorption bands can be observed. Due to the lower number of absorption bands present in the FTIR spectra measured in the new designed thin layer flow cell, it can be concluded that despite the high IR signal no new insights on the reac-tion mechanism of the carbon dioxide reduction reaction can be acquired.