scholarly journals Electrochemical and Molecular Assessment of Quinones as CO2-Binding Redox Molecules for Carbon Capture

2022 ◽  
Author(s):  
Fritz Simeon ◽  
Michael C. Stern ◽  
Kyle M. Diederichsen ◽  
Yayuan Liu ◽  
Howard J. Herzog ◽  
...  
Keyword(s):  
Carbon Capture ◽  
Molecular Assessment ◽  
Redox Molecules

scholarly journals Electrochemical and Molecular Assessment of Quinones as CO2-Binding Redox Molecules for Carbon Capture

2021 ◽  
Author(s):  
Fritz Simeon ◽  
Michael C. Stern ◽  
Kyle M. Diederichsen ◽  
Yayuan Liu ◽  
Howard J. Herzog ◽  
...  
Keyword(s):  
Carbon Capture ◽  
Peak Height ◽  
Peak Position ◽  
Sweep Rate ◽  
Practical Implementation ◽  
Reduction Wave ◽  
Electrochemical Cycling ◽  
Equilibrium Shift ◽  
Lower Vapor Pressure ◽  
Redox Molecules

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone-CO2 complex formation. The peak position and peak height of the first re-duction wave were unchanged, indicating no formation of complexes between the semiquinones and CO2. The relative heights of both reduction waves remained constant. In the case of strongly complexing quinones, the second reduction wave disappeared while the peak height of the first reduction wave approximately doubled, indicating that the two electrons transferred simultaneously at this potential. The observed voltammograms were rationalized through several equilibrium arguments. Both weakly and strongly complexing quinones underwent either stepwise or concerted mechanisms of oxidation and CO2 dissociation depending on the sweep rate in the cyclic voltammetric experiments. Relative to stepwise oxidation, the concerted process requires a more positive electrode potential to remove the electron from the carbonate complexes to release CO2 and regenerate the quinone. For weakly complexing quinones, the stepwise process corresponds to oxidation of the uncomplexed dianion and accompanying equilibrium shift, while for strongly complexing quinones the stepwise process would correspond to the oxidation of mono(carbonate) dianion to the complexed semiquinone and accompanying equilibrium shift. This study provides a mechanistic interpretation of the interactions that lead to the formation of quinone-CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.

Lymphatic Mapping and Sentinel Node Identification for Colorectal Cancer

Swiss Surgery ◽  
2001 ◽  
Vol 7 (6) ◽  
pp. 252-255 ◽  
Author(s):  
Ota ◽  
Lin
Keyword(s):  
Sentinel Node ◽  
Lymphatic Mapping ◽  
Primary Treatment ◽  
Stage Iii ◽  
Nodal Disease ◽  
Node Negative ◽  
Intraoperative Procedures ◽  
Sentinel Node Identification ◽  
Node Metastases ◽  
Molecular Assessment

The primary treatment of resectable CRC is surgical resection. Postoperative adjuvant therapies are recommended when lymph node metastases are found (stage III). There is evidence that about 20% of node negative CRC cases (stage II) are understaged, i.e., they are actually node positive (stage III). New intraoperative procedures (lymphatic mapping and sentinel node identification) that are able to detect occult macro- and micrometastases. Molecular assessment of nodal disease should improve the current staging criteria for colon cancer and could influence recommendation for adjuvant treatment.

CO2 Reduction to Propanol by Copper Foams: A Pre- and Post-Catalysis Study

2020 ◽  
Author(s):  
Jennifer A. Rudd ◽  
Ewa Kazimierska ◽  
Louise B. Hamdy ◽  
Odin Bain ◽  
Sunyhik Ahn ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Photoelectron Spectroscopy ◽  
Carbon Capture ◽  
Surface Composition ◽  
Co2 Reduction ◽  
Structural Rearrangement ◽  
Copper Electrode ◽  
Ex Situ ◽  
X Ray ◽  
Copper Electrodes

The utilization of carbon dioxide is a major incentive for the growing field of carbon capture. Carbon dioxide could be an abundant building block to generate higher value products. Herein, we describe the use of porous copper electrodes to catalyze the reduction of carbon dioxide into higher value products such as ethylene, ethanol and, notably, propanol. For <i>n</i>-propanol production, faradaic efficiencies reach 4.93% at -0.83 V <i>vs</i> RHE, with a geometric partial current density of -1.85 mA/cm<sup>2</sup>. We have documented the performance of the catalyst in both pristine and urea-modified foams pre- and post-electrolysis. Before electrolysis, the copper electrode consisted of a mixture of cuboctahedra and dendrites. After 35-minute electrolysis, the cuboctahedra and dendrites have undergone structural rearrangement. Changes in the interaction of urea with the catalyst surface have also been observed. These transformations were characterized <i>ex-situ</i> using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. We found that alterations in the morphology, crystallinity, and surface composition of the catalyst led to the deactivation of the copper foams.

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