文章信息/Info

Title:

Surface Oxygen Vacancy Based Photocatalysts for Nitrogen Fixation

作者:

毛成梁; 張禮知

華中師范大學化學學院 環境與應用化學研究所 農藥與化學生物學教育部重點實驗室，湖北 武漢430079

Author(s):

Mao Chengliang; Zhang Lizhi

Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental & Applied Chemistry,College of Chemistry, Central China Normal University, Wuhan 430079, China

關鍵詞:

光催化; 固氮; 氧空位; 鹵氧鉍; 氫化氧化鈦

Keywords:

photocatalysis;  nitrogen fixation;  oxygen vacancy;  bismuth oxyhalogenide;  hydrogenated titania

DOI:

10.7502/j.issn.1674-3962.2019.02.01

文獻標志碼:

A

摘要:

合成氨是基本的化工過程，對地球能源、環境和生命過程至關重要。Harbor�睟osch過程利用Fe催化劑開創性地實現了氮氣還原固定為氨。由于氮氣N≡≡N三鍵化學性質穩定，該反應需要在高溫高壓條件才能實現有效氮氣固定。近年來，太陽能驅動的光催化固氮以其綠色溫和的反應條件受到了廣泛關注。最近，作者團隊以鹵氧鉍和釕(Ru)/氫化氧化鈦為模型催化劑，提出氧空位電子可有效活化氮氣，即氧空位對氮氣的直接電子傳遞或者氧空位電子經由Ru納米晶傳遞給吸附態分子氮能有效弱化氮氣N≡≡N三鍵，結合高效太陽光全光譜吸收材料，將光催化合成氨效率提高至接近傳統熱催化效率，為高效太陽光驅動固氮提供了新途徑。從氧空位活性位點的構建出發，總結概括了含缺陷（尤其是氧空位）材料在光催化固氮的前沿進展，歸納了氧空位、氧空位和傳統過渡金屬中心耦合對氮氣活化的機理。最后，基于對以上機理的理解，總結展望了光催化固氮面臨的機遇與挑戰，提出了可行的新型高效光催化固氮材料設計思路。

Abstract:

Ammonia synthesis is a process of vital importance to energy, environment and lives on earth. The industrial paradigm of Harbor�睟osch process utilizes Fe as catalyst realizing large�瞫cale nitrogen fixation. Because of the robust N≡≡N triple bond of the molecular nitrogen, this reaction (N2+3H2 = 2NH3) occurs at high pressure and temperature. In recent years, the facile and “green” alternate of photocatalytic nitrogen fixation has been paid much attention. Recently, we reported that the excess electrons in oxygen vacancies (OV) could activate molecular nitrogen effectively via ① the direct electron transfer from surface oxygen vacancy to OV adsorbed N2 on catalysts such as BiOCl and BiOBr, and ② the indirect electron donation from OV to Ru and then to N2 bonded on Ru within the K/Ru/TiO2-xHx catalyst. By embedding the OV into materials of broad�瞫pectrum light absorbance, we obtained a light�瞕riven reactivity comparable to that of thermal Harbor�睟osch process using the K/Ru/TiO2-xHx catalyst, which provides a new avenue for efficient solar ammonia synthesis. In this paper, we reviewed the recent advances in defects (especially the OV) promoted photocatalytic nitrogen fixation, including the nitrogen fixation mechanism of OV within various metal oxides and the coupling effect of OV to traditional active centers such as transition metals, aiming to reach a fundamental understanding of OV based nitrogen fixation. At last, we summarize the opportunities and challenges in the photocatalytic nitrogen fixation and propose possible pathways for the design of highly efficient photocatalysts.