Deng Xiaohui, Yang Yongpeng, Wang Lei, Fu Xian-Zhu, Luo Jing-Li
Shenzhen Key Laboratory of Polymer Science and Technology Guangdong Research Center for Interfacial Engineering of Functional Materials College of Materials Science and Engineering Shenzhen University Shenzhen 518061 China.
Henan Institute of Advanced Technology Zhengzhou University Zhengzhou 450001 China.
Adv Sci (Weinh). 2021 Feb 1;8(7):2004523. doi: 10.1002/advs.202004523. eCollection 2021 Apr.
Electrochemical nitrate reduction (NITRR) offers a promising alternative toward nitrogen recycling and ammonia production under ambient conditions, for which highly active and selective electrocatalyst is desired. In this study, metallic cobalt nanoarrays as facilely prepared from the electrochemical reduction of Co(OH) nanoarrays (NAs) are demonstrated to exhibit unprecedented NH producing capability from catalyzing NITRR. Benefitting from the high intrinsic activity of Co, intimate contact between active species and conductive substrate and the nanostructure which exposes large number of active sites, the Co-NAs electrode exhibits current density of -2.2 A cm and NH production rate of 10.4 mmol h cm at -0.24 V versus RHE under alkaline condition and significantly surpasses reported counterparts. Moreover, the close-to-unity (≥96%) Faradaic efficiency (FE) toward NH is achieved over wide application range (potential, NO concentration and pH). Density function theory calculation reveals the optimized adsorption energy of NITRR intermediates on Co surface over Co(OH). Furthermore, it is proposed that despite the sluggish kinetics of Volmer step (HO → *H + *OH) which provides protons in conventional hydrogenation mechanism, the proton-supplying water dissociation process on Co surface is drastically facilitated following a concerted water dissociation-hydrogenation pathway.
电化学硝酸盐还原（NITRR）为环境条件下的氮循环利用和氨生产提供了一种有前景的替代方法，为此需要高活性和选择性的电催化剂。在本研究中，通过电化学还原Co(OH)纳米阵列（NAs）轻松制备的金属钴纳米阵列被证明在催化NITRR时展现出前所未有的产氨能力。受益于Co的高本征活性、活性物种与导电基底之间的紧密接触以及暴露大量活性位点的纳米结构，Co-NAs电极在碱性条件下相对于可逆氢电极（RHE）在-0.24 V时表现出-2.2 A cm的电流密度和10.4 mmol h cm的产氨速率，显著超过已报道的同类电极。此外，在较宽的应用范围（电位、NO浓度和pH值）内实现了接近单位值（≥96%）的氨法拉第效率（FE）。密度泛函理论计算揭示了NITRR中间体在Co表面相对于Co(OH)的优化吸附能。此外，研究表明，尽管在传统加氢机制中提供质子的Volmer步骤（HO → *H + *OH）动力学缓慢，但Co表面的质子供应水离解过程通过协同水离解-加氢途径得到了极大促进。
