Department of Chemistry, State Key Laboratory of Marine Pollution, City University of Hong Kong, Hong Kong, 999077, P. R. China.
Division of Science, Engineering and Health Study, School of Professional Education and Executive Development (PolyU SPEED), The Hong Kong Polytechnic University, Hong Kong, 999077, P. R. China.
Adv Mater. 2023 Jun;35(24):e2211856. doi: 10.1002/adma.202211856. Epub 2023 Apr 28.
Ammonia is an indispensable commodity in the agricultural and pharmaceutical industries. Direct nitrate-to-ammonia electroreduction is a decentralized route yet challenged by competing side reactions. Most catalysts are metal-based, and metal-free catalysts with high nitrate-to-ammonia conversion activity are rarely reported. Herein, it is shown that amorphous graphene synthesized by laser induction and comprising strained and disordered pentagons, hexagons, and heptagons can electrocatalyze the eight-electron reduction of NO to NH with a Faradaic efficiency of ≈100% and an ammonia production rate of 2859 µg cm h at -0.93 V versus reversible hydrogen electrode. X-ray pair-distribution function analysis and electron microscopy reveal the unique molecular features of amorphous graphene that facilitate NO reduction. In situ Fourier transform infrared spectroscopy and theoretical calculations establish the critical role of these features in stabilizing the reaction intermediates via structural relaxation. The enhanced catalytic activity enables the implementation of flow electrolysis for the on-demand synthesis and release of ammonia with >70% selectivity, resulting in significantly increased yields and survival rates when applied to plant cultivation. The results of this study show significant promise for remediating nitrate-polluted water and completing the NO cycle.
氨是农业和制药行业不可或缺的商品。直接将硝酸盐还原为氨的电还原是一种分散的途径，但受到竞争副反应的挑战。大多数催化剂是基于金属的，而具有高硝酸盐到氨转化率的无金属催化剂很少有报道。本文表明，通过激光诱导合成的包含应变和无序五边形、六边形和七边形的无定形石墨烯可以电催化将 NO 还原为 NH，法拉第效率约为 100%，在相对于可逆氢电极的 -0.93 V 下氨的生成速率为 2859 µg cm h。X 射线对分布函数分析和电子显微镜揭示了无定形石墨烯的独特分子特征，有利于 NO 还原。原位傅里叶变换红外光谱和理论计算确立了这些特征在通过结构弛豫稳定反应中间体方面的关键作用。增强的催化活性使按需合成和释放氨的流动电解得以实现，选择性>70%，当应用于植物培养时，产量和存活率显著提高。这项研究的结果表明，在修复硝酸盐污染的水和完成 NO 循环方面具有很大的潜力。
