Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA.
Department of Urban and Environmental Engineering, Graduate School of Carbon Neutrality, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan, 44919, Republic of Korea.
Nat Commun. 2023 Feb 14;14(1):823. doi: 10.1038/s41467-023-36318-1.
Nitrate is a ubiquitous aqueous pollutant from agricultural and industrial activities. At the same time, conversion of nitrate to ammonia provides an attractive solution for the coupled environmental and energy challenge underlying the nitrogen cycle, by valorizing a pollutant to a carbon-free energy carrier and essential chemical feedstock. Mass transport limitations are a key obstacle to the efficient conversion of nitrate to ammonia from water streams, due to the dilute concentration of nitrate. Here, we develop bifunctional electrodes that couple a nitrate-selective redox-electrosorbent (polyaniline) with an electrocatalyst (cobalt oxide) for nitrate to ammonium conversion. We demonstrate the synergistic reactive separation of nitrate through solely electrochemical control. Electrochemically-reversible nitrate uptake greater than 70 mg/g can be achieved, with electronic structure calculations and spectroscopic measurements providing insight into the underlying role of hydrogen bonding for nitrate selectivity. Using agricultural tile drainage water containing dilute nitrate (0.27 mM), we demonstrate that the bifunctional electrode can achieve a 8-fold up-concentration of nitrate, a 24-fold enhancement of ammonium production rate (108.1 ug h cm), and a >10-fold enhancement in energy efficiency when compared to direct electrocatalysis in the dilute stream. Our study provides a generalized strategy for a fully electrified reaction-separation pathway for modular nitrate remediation and ammonia production.
硝酸盐是农业和工业活动产生的一种普遍存在的水污染物。与此同时，将硝酸盐转化为氨为氮循环所带来的环境和能源挑战提供了一个有吸引力的解决方案，即将污染物转化为无碳能源载体和重要的化学原料。由于硝酸盐浓度较低，传质限制是从水流中高效将硝酸盐转化为氨的关键障碍。在这里，我们开发了一种双功能电极，将硝酸盐选择性氧化还原电吸附剂（聚苯胺）与电催化剂（氧化钴）结合在一起，用于硝酸盐到铵的转化。我们通过仅电化学控制证明了硝酸盐的协同反应分离。可以实现大于 70mg/g 的电化学可逆硝酸盐吸收，电子结构计算和光谱测量提供了对氢键对硝酸盐选择性的潜在作用的深入了解。使用含有稀硝酸盐（0.27mM）的农业排水瓦，我们证明双功能电极可以实现硝酸盐的 8 倍浓缩，铵的产生速率提高 24 倍（108.1μg h cm），与稀流中的直接电催化相比，能量效率提高了 10 倍以上。我们的研究为模块化硝酸盐修复和氨生产的全电化反应分离途径提供了一种通用策略。
