Electrochemical Reduction of CO2

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The aim of this three-year research project is to gain deeper insight into bimetallic catalysts for the reduction of CO2 to hydrocarbons. These catalysts will be optimised w.r.t. high stability, efficiency and feasibility of large-scale applications. Products of this reaction such as methanol can be directly used as fuel or be further synthesised to more efficient and clean fuels like Oxymethylenether.Consequently, this research project will focus on transition metals, e.g. copper, gold, and silver, which have already shown promise for an efficient and selective CO2 electroreduction. Copper is able to directly reduce CO2 to hydrocarbons, gold and silver have CO as main product. However, these metals still have flaws preventing large-scale industrial use. E.g., Copper has a poor selectivity as well as a low energy-efficiency due to a large overpotential. In addition, it is poisoned by a carbon layer on the electrode. In contrast, gold has a high stability against such poisoning, but is very costly. Silver has a low overpotential and good selectivity, but CO is easily desorbed leading to a less hydrocarbons. (Zhang, Zhao, and Gong 2017; Zhu, Liu, and Qiao 2016)In order to overcome these critical flaws, the novel approach of alloying will be used in this research project. The aforementioned metals will be alloyed with other transition metals to generate an efficient direct reduction to methanol in the case of gold and silver. This might be achieved by e.g. rhodium, indium, platinum, palladium or cobalt. Concerning copper, the aim is to create an alloy combination with a higher stability against poisoning as well as a better energy-efficiency. Possible alloys would be copper and tin as well as the metals mentioned above with gold and silver.In addition to developing a more efficient and versatile bimetal catalyst, the influence of the employed substrate and preparation method will be investigated. Depending on the desired structure and characteristics, different electrochemical methods for the preparation of the catalyst will be tested. A special focus will be set on the physical interaction between catalyst and substrate. To ensure a stable and efficient reaction on an industrial scale, the catalyst must be stable against poisoning and flow conditions in the reactor. The proposed research aims at preventing a loose connection between catalyst and substrate which would result in a system prone to breakdowns or losses in selectivity and thus efficiency quickly over time. Either way, such a system cannot be used on a larger scale.