金红石TiO_(2)(110)表面的低温氨气合成  

Low Temperature Ammonia Synthesis from Atomic N and Water on Rutile TiO_(2)(110)

作　　者：赖悦苗 郭庆 陈晓 Yuemiao Lai;Qing Guo;Xiao Chen(Shenzhen Key Laboratory of Energy Chemistry&Department of Chemistry,Southern University of Science and Technology,Shenzhen 518055,China)

机构地区：[1]南方科技大学化学系,深圳市能源化学重点实验室,深圳518055

出　　处：《Chinese Journal of Chemical Physics》2023年第3期272-278,I0001-I0005,I0099,共13页化学物理学报（英文）

基　　金：supported by the National Key R&D Program of China(No.2018YFE0203002);the National Natural Science Foundation of China(No.22173041,No.22173042,No.21973037,NSFC Center for Chemical Dynamics);the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB17000000);the Shenzhen Science and Technology Innovation Committee(No.JCYJ2019080914021660,No.ZDSYS20200421111001787);the Guangdong Innovative&Entrepreneurial Research Team Program(No.2019ZT08L455,No.2019JC01X091);the International Partnership Program of Chinese Academy of Science(No.121421KYSB 20170012);Innovation Program for Quantum Science and Technology(No.2021ZD0303304).

摘　　要：传统工业上,合成氨反应往往在高温高压下进行,造成了大量的能源消耗.因此,有必要发展绿色可持续的新方法,从而在温和条件下实现氨气的高效合成.从原子分子层面上理解合成氨的微观反应过程有利于高效高选择性催化剂的开发.本文系统探究了在金红石TiO_(2)(110)模型体系表面氨气生成的微观反应过程.利用程序升温脱附谱技术,发现了在金红石TiO_(2)(110)表面共吸附氮原子和水分子之后,在升温过程中,氨气可以生成并在400 K左右从五配位Ti^(4+)位(Ti_(5c))上脱附出去,这表明在金红石TiO_(2)(110)表面氨气的确可以在低温下生成.结果表明,桥氧列上的羟基和Ti_(5c)位上的水分子均可以提供氨气生成所需的氢原子.氢原子在金红石TiO_(2)(110)表面的迁移在氨气的生成过程中扮演了重要作用,通过改变水分子的覆盖度,氢原子的迁移方式会随着水分子覆盖度的改变而发生变化.当水分子的覆盖度较低时,氢键网络在金红石TiO_(2)(110)表面上尚未建立,氢原子主要以直接跃迁的方式迁移侄氮原子附近,其对应的扩散能垒约为1 eV:随着水分子覆盖度的逐渐增加,氢键网络在金红石TiO_(2)(110)表面逐步建立起来,此时氢原子更倾向于在氢键网络的辅助下迁移至氮原子附近,其对应的扩散能垒仅为0.2~0.3 eV.此外,吸附在氮原子附近的水分子也有可能直接与氮原子发生反应生成氨气.因此,在金红石TiO_(2)(110)表面,氮原子可能存在三种不同的加氢过程.实验结果不仅有助于深入理解合成氨反应中的加氢过程,同时也对催化剂的设计和优化提供了一种新思路.We have investigated the formation of ammonia(NH_(3))from atomic N and water(H_(2)O)on a rutile(R)-TiO_(2)(110)surface using the temperature-programed desorption method.The formation of NH_(3) can be detected after coadsorption of atomic N and H_(2)O on the R-TiO_(2)(110)surface,desorbing from the 5-fold coordinated Ti^(4+)(Ti_(5c))sites at about 400 K,demonstrating that the NH3 formation on RTiO_(2)(110)is feasible at low surface temperature.During the process,both hydroxyl groups at the bridging oxygen rows and H_(2)O on the Ti5c sites contribute to the formation of NH_(3),which are affected by H_(2)O coverage.At low H_(2)O coverage,the direct hopping of hydrogen atoms may be the dominant process for hydrogen transfer;while H_(2)O-assisted hydrogen atoms diffusion may be preferred at high H_(2)O coverage.Our result will be of significant help to get a deeper insight into the fundamental understandings of hydrogenation processes during the NH3 synthesis.

关 键 词：氨气 氢原子转移 程序升温脱附谱 金红石TiO_(2)(110) 

分 类 号：TQ113.2[化学工程—无机化工]