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K. Roohi
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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.
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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.
IIn the past decades, the rapid development of industry and economy leads to heavy dependence on fossil fuels which causes increasing concentration of CO2 in atmosphere. Now, excessive CO2 emission has accelerated global warming and caused a series of irreversible environmental problems. To address this problem, electrochemical conversion of CO2 is considered one of the most promising strategies to due to its mild operating conditions, utilization of renewable sources of energy and controllability of the process. However, CO2 reduction faces many difficulties which requires active catalysts to achieve effective conversion. Among all the catalysts, Copper (Cu)-based Metal-Organic Frameworks (MOFs) become veryattracting candidates due to their high porosity, tunable structure and special properties to convert CO2 into various hydrocarbons. In particular, two-dimension (2D) Cu-MOFs can further improve the electrical conductivity and catalytic activity. In this study, three types of Cu-based MOFs are studied as catalysts for CO2 reduction reaction (CO2RR). Among them, Cu-BTC is a conventional 3D MOF, Cu-HAB and Cu-HHTP belong to 2D MOFs. In particular, Cu-HAB has not been used as catalyst for CO2 reduction before. To investigate their catalytic performance for CO2 reduction, the surface morphologies and bond structures were first characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR). Then Linear sweep voltammetry (LSV), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) were used to examine the electrochemical performance and stability of them. In the last, the product selectivity of Cu-HAB and Cu-HHTP wastested using Gas Chromography (GC) and Nuclear Magnetic Resonance (NMR). From the results, 2D MOFs show higher catalytic activity, capacitance and conductivity which suggest 2D structure is beneficial for catalytic process. Especially Cu-HAB shows the best conductivity and catalytic activity due to presence of Cu-N4 coordination in the MOF structure as well as smaller particles. But from the point of view of product selectivity, Cu-HHTP performs better than Cu-HAB which may indicate Cu-O4 sites can better engage with CO2 molecule and transfer it to other products.
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IIn the past decades, the rapid development of industry and economy leads to heavy dependence on fossil fuels which causes increasing concentration of CO2 in atmosphere. Now, excessive CO2 emission has accelerated global warming and caused a series of irreversible environmental problems. To address this problem, electrochemical conversion of CO2 is considered one of the most promising strategies to due to its mild operating conditions, utilization of renewable sources of energy and controllability of the process. However, CO2 reduction faces many difficulties which requires active catalysts to achieve effective conversion. Among all the catalysts, Copper (Cu)-based Metal-Organic Frameworks (MOFs) become veryattracting candidates due to their high porosity, tunable structure and special properties to convert CO2 into various hydrocarbons. In particular, two-dimension (2D) Cu-MOFs can further improve the electrical conductivity and catalytic activity. In this study, three types of Cu-based MOFs are studied as catalysts for CO2 reduction reaction (CO2RR). Among them, Cu-BTC is a conventional 3D MOF, Cu-HAB and Cu-HHTP belong to 2D MOFs. In particular, Cu-HAB has not been used as catalyst for CO2 reduction before. To investigate their catalytic performance for CO2 reduction, the surface morphologies and bond structures were first characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR). Then Linear sweep voltammetry (LSV), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Chronoamperometry (CA) were used to examine the electrochemical performance and stability of them. In the last, the product selectivity of Cu-HAB and Cu-HHTP wastested using Gas Chromography (GC) and Nuclear Magnetic Resonance (NMR). From the results, 2D MOFs show higher catalytic activity, capacitance and conductivity which suggest 2D structure is beneficial for catalytic process. Especially Cu-HAB shows the best conductivity and catalytic activity due to presence of Cu-N4 coordination in the MOF structure as well as smaller particles. But from the point of view of product selectivity, Cu-HHTP performs better than Cu-HAB which may indicate Cu-O4 sites can better engage with CO2 molecule and transfer it to other products.