Efficient nitrate-to-ammonia transformation through a direct eight-electron reduction
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ficient nitrate-to-ammonia transformation through a direct eight-electron reduction *
Jiaxin Yao & Junmin Yan
Key Laboratory of Automobile Materials, Ministry of Education, School of Materials Science and Engineering, Jilin University, Changchun 130022, China Received August 4, 2020; accepted August 11, 2020; published online September 14, 2020
Citation:
Yao J, Yan J. Efficient nitrate-to-ammonia transformation through a direct eight-electron reduction. Sci China Chem, 2020, 63, https://doi.org/10.1007/ s11426-020-9848-3
Ammonia (NH3), as one of the most necessary chemical materials, is mainly produced via the Haber-Bosch process from hydrogen (H2) and nitrogen (N2), which requires harsh synthesis conditions and aggravates energy consumption and greenhouse effect [1]. As an alternative, electrocatalytic N2 reduction to NH3 has evolved for years. However, most of electrocatalysts are confined to poor NH3 synthesis efficiency restricted by the strong N≡N triple bonds, the competition of hydrogen evolution reaction (HER), and limited N2 solubility in H2O [2]. In the exploration for an alternative nitrogen source except N2 to synthesize NH3, the nitrate − anion (NO3 ) brings about extensive attention because the −1 dissociation energy of N=O bonds (204 kJ mol ) is lower − than N≡N triple bonds [3], and the enrichment of NO3 in water resources causes the environmental pollution and further infringes the human health [4]. Thus, selective con− version from NO3 to NH3 through the eight-electron reduction, if proceeding under ambient conditions in the H2Obased system, may offer a green technology for the NH3 manufacture and simultaneously alleviate the energy and pollution problems. Several electrocatalytic [5] and photocatalytic [6] systems with different heterogeneous catalysts have been proposed, while most of them tend to produce N2 via five-electron − reduction of NO3 rather than the desired eight-electron re− duction. In addition, the practical potential of NO3 to NH3 is
below the HER potential, which leads to the H2 generation, and accordingly, suppresses the NH3 Faradaic efficiency (FE) [7]. Therefore, developing an efficient electrocatalyst possessing brilliant conversion rates as well as high selectivity is full of challenges. Aiming for this, Wang and coworkers [8] at South China University of Technology report − a direct eight-electron reduction from NO3 to NH3 catalyzed by Cu-incorporated crystalline 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) with the outstanding selectivity and yield rates. The Cu-PTCDA was synthesized by a simple autoreduction method, and the authors applied the technologies including microscopes and synchrotron to explore the morphology, composition and bonding environment of Cu incorporated in PTCDA, which all confirm the successful incorporation of Cu into the PTCDA. − The NO3 -to-NH3 conversion performances have a close relationship with the amount and incorporation approach of Cu in PTCDA, where O-Cu-PTCDA (autoreduction time: 1,200 s) exhibits the brilliant NH3 production
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