摘要
以可再生电能为能源, H2O为质子和电子源,温和条件下将氮气(N2)还原为氨气(NH3)将成为替代传统高能耗合成氨工艺(Haber-Bosch方法)的有效途径之一. N2分子的高反应活化能和析氢反应(hydrogen evolution reaction,HER)导致的产NH3速率和法拉第效率低,是目前电催化氮气还原(nitrogen reduction reaction, NRR)合成NH3面临的主要挑战.过渡金属基催化剂可通过反馈π电子过程吸附、活化N2分子,然而d轨道电子同样有利于质子吸附,进而促进HER竞争反应,导致合成NH3法拉第效率降低.碳基纳米材料因其出色的电导率、优异的化学稳定性以及可调的电子结构、形貌特征,成为当前电催化NRR合成NH3领域的研究热点.结合上述研究工作,本文从电催化NRR合成NH3机理出发,介绍了碳基纳米材料的种类和结构,重点综述了碳基纳米材料电催化NRR合成NH3活性提高策略,包括杂原子掺杂、单原子活性中心设计、缺陷工程.最后总结了该领域目前存在的问题与挑战以及未来发展趋势.
Ammonia(NH3) has been widely utilized as fertilizer in agriculture and synthetic building blocks for a couple of industrial products. It also works as a caron-free fuel in internal combustion engines. Therefore, NH3 is of considerable significance for modern human community with over 160 million tons synthesized every year. However, NH3 synthesis was commonly carried out by the energy-intensive and fossil fuel-dependent Haber-Bosch process where the high-cost of clean and pure H2 produced from fossil fuel resources and huge energy inputs are needed. In addition, only 10%-15% NH3 conversion efficiency can be achieved by single reaction even at the pressures as high as 40 MPa. The harsh reaction conditions and relatively low conversion efficiency as well as the valuable and fossil fuel-dependent reactant of H2 cause the Haber-Bosch process to be currently one of the largest global energy consumers and greenhouse gas emitters, contributed to 1.2% of the global anthropogenic CO2 emissions. In this regard, it is of great importance to develop alternative sustainable approaches for NH3 synthesis with cheap and abundant H resources(e.g., H2 O) under mild conditions.Electrochemical nitrogen reduction reaction(NRR) to NH3 under mild conditions powered by renewable electricity is a potential alternative to the energy-intensive and fossil fuel-dependent Haber-Bosch process. The intrinsic inertness of N2 molecule and competition of hydrogen evolution reaction(HER) in aqueous solutions are the major challenges for electrochemical NRR. In order to overcome obstacles and facilitate this sluggish reaction, extensive attentions have been given to explore efficient and robust electrocatalysts. Although transition metal-based catalysts can solve the kinetic limitation of N≡N activation through the π-back donation process, the d-orbital electrons in transition metal atoms also favor the formation of metal-H bond and therefore boost the undesired HER side reaction. Carbon-based materials featuring the tunable electronic structure,
作者
于丰收
周志翔
张鲁华
Fengshou Yu;Zhixiang Zhou;Lu-Hua Zhang(National Local Joint Engineering Laboratory for Energy Conservation of Chemical Process Integration and Resources Utilization,School of Chemical Engineering and Technology,Hebei University of Technology,Tianjin 300131,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2021年第24期3111-3122,共12页
Chinese Science Bulletin
基金
国家自然科学基金(21905073,22008048)
河北省海外高层次人才百人计划(E2019050015)资助。
关键词
电催化
氮气还原
氨合成
碳基纳米催化剂
结构缺陷设计
electrocatalysis
nitrogen reduction
ammonia synthesis
carbon-based nanomaterials
defect engineering
