@Article{icces.2024.012577,
AUTHOR = {Wenzhen Li, Hengzhou Liu, Yifu Chen, Shuang Gu},
TITLE = {Green Ammonia-Mediated CO<sub>2</sub> Capture and Conversion to Valuable Chemicals},
JOURNAL = {The International Conference on Computational \& Experimental Engineering and Sciences},
VOLUME = {31},
YEAR = {2024},
NUMBER = {1},
PAGES = {1--1},
URL = {http://www.techscience.com/icces/v31n1/58741},
ISSN = {1933-2815},
ABSTRACT = {Direct electrochemical conversion of CO<sub>2</sub> capture solutions (instead of gaseous CO<sub>2</sub>) into valuable chemicals can circumvent the energy-intensive CO<sub>2</sub> regeneration and pressurization steps. While commonly used CO<sub>2</sub> capture agents include alkali and amine solutions, ammonia has been rarely investigated. In another aspect, mismanagement of reactive nitrogen (Nr) in waste has emerged as a major problem in water pollution to our ecosystems, causing severe eutrophication and health concerns. Sustainably recovering Nr [such as nitrate (NO<sub>3</sub><sup>−</sup>)-N] and converting it into green ammonia (NH<sub>3</sub>) could mitigate the environmental impacts of Nr and reduce the NH<sub>3</sub> demand from the carbon-intensive Haber-Bosch process, as well as a possible CO<sub>2</sub> capture agent due to its alkaline nature.    In this talk, we will present our rencet research on integration of electrodialysis and electrocatalysis for ammonia synthesis from dilute waste Nr sources [1], and green ammonia-mediated CO<sub>2</sub> capture (to ammonium bicarbonate, NH<sub>4</sub>HCO<sub>3</sub>) and subsequent reduction to ammonium formate (NH<sub>4</sub>HCO<sub>2</sub>) as a new approach to CO<sub>2</sub> capture and utilization (CCU) [2]. We have demonstrated a record-high NO<sub>3</sub><sup>−</sup>-to-NH<sub>3</sub> performance in a scalable, versatile, and cost-effective membrane-free alkaline electrolyzer (MFAEL): an unprecedented NH<sub>3</sub> partial current density of 4.22 ± 0.25 A cm<sup>−2</sup> with a faradaic efficiency of 84.5 ± 4.9%. We also discovered that an ammonium bicarbonate (NH<sub>4</sub>HCO<sub>3</sub>)-fed electrolyzer with an anion exchange membrane (AEM) outperforms the state-of-the-art KHCO<sub>3</sub> electrolyzer with a bipolar membrane (BPM) owing to its favorable thermal decomposition property, which allows for a 3-fold increase in the in situ CO<sub>2</sub> concentration, a maximum 23% increase in formate faradaic efficiency, and a 35% reduction in cell voltage by substituting BPM with the AEM. Our integrated process by combining NH<sub>4</sub>HCO<sub>3</sub> electrolysis with CO<sub>2</sub> capturing by on-site generated green ammonia from the electro-reduction of nitrate in MFAEL has shown a remarkable 99.8% utilization of CO<sub>2</sub> capturing agent. Our recent progress in this direction will also be briefly presented. Such a multi-purpose process may offer a sustainable route for the simultaneous removal of Nr wastes and streamlined CO<sub>2</sub> capturing and upgrading to valuable chemicals.},
DOI = {10.32604/icces.2024.012577}
}