Chen Yingkai, Luo Jiayu, Ling Li, Zhan Zhengshuo, Liu Jiutan, Gao Zongjun, Lam Jason Chun-Ho, Feng Chunhua, Lei Yang
School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
Environ Sci Ecotechnol. 2024 Sep 13;23:100492. doi: 10.1016/j.ese.2024.100492. eCollection 2025 Jan.
Electrochemical nitrate reduction to ammonia (ENRA) is gaining attention for its potential in water remediation and sustainable ammonia production, offering a greener alternative to the energy-intensive Haber-Bosch process. Current research on ENRA is dedicated to enhancing ammonia selectively and productivity with sophisticated catalysts. However, the performance of ENRA and the change of catalytic activity in more complicated solutions (i.e., nitrate-polluted groundwater) are poorly understood. Here we first explored the influence of Ca and bicarbonate on ENRA using commercial cathodes. We found that the catalytic activity of used Ni or Cu foam cathodes significantly outperforms their pristine ones due to the evolution of new catalytic species on used cathodes during ENRA. In contrast, the nitrate conversion performance with nonactive Ti or Sn cathode is less affected by Ca or bicarbonate because of their original poor activity. In addition, the coexistence of Ca and bicarbonate inhibits nitrate conversion by forming scales (CaCO) on the -formed active sites. Likewise, ENRA is prone to fast performance deterioration in treating actual groundwater over continuous flow operation due to the presence of hardness ions and possible organic substances that quickly block the active sites toward nitrate reduction. Our work suggests that more work is required to ensure the long-term stability of ENRA in treating natural nitrate-polluted water bodies and to leverage the environmental relevance of ENRA in more realistic conditions.
电化学硝酸盐还原制氨（ENRA）因其在水修复和可持续氨生产方面的潜力而受到关注，为能源密集型的哈伯-博施法提供了一种更绿色的替代方案。目前关于ENRA的研究致力于使用复杂的催化剂提高氨的选择性和生产率。然而，人们对ENRA在更复杂溶液（即硝酸盐污染的地下水）中的性能以及催化活性的变化了解甚少。在此，我们首先使用商业阴极探索了钙和碳酸氢根对ENRA的影响。我们发现，使用过的泡沫镍或泡沫铜阴极的催化活性明显优于其原始阴极，这是由于在ENRA过程中使用过的阴极上会生成新的催化物种。相比之下，对于非活性的钛或锡阴极，由于其原本活性较差，硝酸盐转化性能受钙或碳酸氢根的影响较小。此外，钙和碳酸氢根的共存会通过在生成的活性位点上形成水垢（碳酸钙）来抑制硝酸盐转化。同样，由于存在硬度离子和可能迅速堵塞硝酸盐还原活性位点的有机物质，在连续流动操作处理实际地下水时，ENRA的性能容易快速恶化。我们的工作表明，需要开展更多工作来确保ENRA在处理天然硝酸盐污染水体时的长期稳定性，并在更实际的条件下利用ENRA与环境的相关性。
