Carbonization of 3D- and 2D-MOFs for electrochemical carbon dioxide reduction

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Abstract

Due to global warming, there is a rising demand for green energy storage and green fuels. $CO_2$ reduction can help mitigate these demands by storing energy in chemical bonds, thereby creating fuels that are relatively easy to use and store. In this way, a new carbon cycle can be created. Catalyst materials play a key role in improving the selectivity, productivity and stability of the $CO_2$ reduction reaction ($CO_2RR$). MOFs are an interesting catalyst material for this, as their porosity enables large surface areas and their structure allows for tunable selectivity. 2D-MOFs are especially beneficial due to their higher conductivity and mass permeability compared to 3D-MOFs. Carbonization can be used to improve the limited conductivity and stability of MOFs making them more suitable for $CO_2RR$. This is why this study investigates the effects of carbonization on the catalytic capabilities of 3D and 2D-MOFs for the $CO_2RR$. Therefore, Cu-BTC was carbonized using different parameters. The resulting materials were investigated via a multitude of electrochemical techniques to further understand their catalytic capabilities. The 2D-MOFs Cu-THQ and Cu-HAB were then carbonized and the $CO_2RR$ products of the resulting catalysts were investigated. The analysis of the $CO_2RR$ products created by the different MOF derived catalysts shows that the main influence on the selectivity of these catalyst materials is the size and distribution of the Cu-cluster formed during carbonization. Since SEM and EDS results showed that the Cu-cluster formation is influenced by the applied carbonization parameters, this shows that these parameters can affect the selectivity of the resulting catalyst. A reasoning for why the Cu-clusters influence selectivity is discussed, however this remains to be proven by future work.