Indirect electrochemical reduction of carbon dioxide to carbon nanopowders in molten alkali carbonates: process variables and product properties

Ijije, Happiness V. and Sun, Chenggong and Chen, George Zheng (2014) Indirect electrochemical reduction of carbon dioxide to carbon nanopowders in molten alkali carbonates: process variables and product properties. Carbon, 73 . pp. 163-174. ISSN 0008-6223

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Abstract

Carbon was deposited on a mild steel cathode during electrolysis in the molten mixture of Li2CO3 and K2CO3 (mole ratio: 62:38) under CO2 or mixed N2 and CO2 atmospheres at 3.0–5.0 V and 540–700 °C. In a three-electrode cell, cyclic voltammetry was applied on a platinum working electrode to study the reduction and deposition processes. A two-electrode cell helped correlate electrolysis variables, e.g. temperature and voltage, with the deposition rate, current efficiency, and properties of the deposited carbon powders. High current efficiency (>90%) and deposition rate (>0.11 g cm−2 h−1) were achieved in the study. Elemental analysis of the electro-deposits, following washing with HCl solutions (2.3–7.8 mol L−1), showed carbon as the dominant element (75–95 wt.%) plus oxygen (5–10 wt.%) and small amounts of other elements related to materials of the electrolytic cell. Thermogravimetry detected fairly low onset combustion temperatures (310–430 °C), depending on the electrolysis and acid washing conditions. Amorphous and various nanostructures (sheet, rings and quasi-spheres) were revealed by electron microscopy in carbon samples deposited under different process conditions. The specific surface area of the carbon deposited at 5.0 V and 540 °C was as high as 585 m2 g−1. An analysis of the energy consumption suggests several ways for efficiency improvement so that the electrolytic carbon from CO2 will become commercially attractive.

Item Type: Article
Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Carbon. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Carbon, 73 (2014), doi: 10.1016/j.carbon.2014.02.052
Keywords: Carbon; carbon dioxide; electrolysis; molten salts
Schools/Departments: University of Nottingham UK Campus > Faculty of Engineering > Department of Chemical and Environmental Engineering
Identification Number: https://doi.org/10.1016/j.carbon.2014.02.052
Related URLs:
URLURL Type
http://dx.doi.org/10.1016/j.carbon.2014.02.052UNSPECIFIED
Depositing User: Chen, Professor George Zheng
Date Deposited: 08 Apr 2014 10:34
Last Modified: 13 Sep 2016 17:29
URI: http://eprints.nottingham.ac.uk/id/eprint/2885

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