催化学报 ›› 2018, Vol. 39 ›› Issue (3): 421-430.DOI: 10.1016/S1872-2067(18)63027-X

• 论文 • 上一篇    下一篇

基于镧和铬共掺杂钛酸锶产氢光催化剂构建Z机制全分解水体系

贾玉帅a,b, 赵丹a, 李名润a, 韩洪宪a, 李灿a   

  1. a 中国科学院大连化学物理研究所催化基础国家重点实验室, 洁净能源国家实验室(筹), 辽宁大连 116023;
    b 江西师范大学化学化工学院, 江西南昌 330022
  • 收稿日期:2017-12-23 修回日期:2018-01-19 出版日期:2018-03-18 发布日期:2018-03-10
  • 通讯作者: 韩洪宪, 李灿
  • 基金资助:

    国家自然科学基金(21763013,21473189);国家重点研发计划(2017YFA0204804).

La and Cr Co-doped SrTiO3 as an H2 evolution photocatalyst for construction of a Z-scheme overall water splitting system

Yushuai Jiaa,b, Dan Zhaoa, Mingrun Lia, Hongxian Hana, Can Lia   

  1. a State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, Jiangxi, China
  • Received:2017-12-23 Revised:2018-01-19 Online:2018-03-18 Published:2018-03-10
  • Contact: 10.1016/S1872-2067(18)63027-X
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21763013, 21473189), and the National Key Research and Development Program of China (2017YFA0204804).

摘要:

光催化剂的晶体结构、电子结构、表面结构等都会对自身性质产生决定性的作用,因此认识和理解光催化材料自身结构和光催化性能之间的内在联系有助于设计合成更高效的光催化剂以及光催化复合体系.本文通过聚合络合法和溶胶凝胶水热法分别制备了镧和铬共掺杂的SrTiO3光催化剂,标记为SrTiO3(La,Cr)-PCM和SrTiO3(La,Cr)-SHM.在碘化钠或甲醇作为牺牲试剂的产氢反应中,担载Pt的SrTiO3(La,Cr)-SHM样品显示了光催化活性,而担载Pt的SrTiO3(La,Cr)-PCM样品活性很低,甚至无活性.我们将这两种材料分别作为产氢光催化剂与三氧化钨耦合构建Z机制全分解水体系.研究发现,只有Pt/SrTiO3(La,Cr)-SHM|I-/IO3-|PtOx/WO3体系观察到了氢气和氧气的产生.在第一个10 h的循环反应中,产生的H2/O2摩尔比为3.7,明显高于水分解H2/O2为2的化学计量比.这是因为在反应起始时加入的是NaI,质子还原产氢反应占据了主导.随着氢气的不断产生,部分I-被氧化成了IO3-,而IO3-的存在就可以驱动氧气的产生,由于溶液中I-/IO3-氧化还原电的共存就可以持续驱动氢气和氧气的同时生成.为了测试体系的稳定性,我们将前面产生的气体完全抽空后又进行第二次10 h的循环反应,总共进行三次循环反应.在第一次循环过程中氢气、氧气生成速率分别为9.1和2.4 mmol h-1,第二次循环其速率分别为9.9和3.7 mmol h-1,第三次循环速率分别达到10.4和4.9 mmol h-1.此外,通过三次循环后H2/O2摩尔比为2.1,接近水分解的化学计量比.
结合紫外可见漫反射光谱和Mott-Schottky曲线可以确定两种样品的能带位置.从能带位置示意图可知,两种样品都具有足够负的导带电势还原质子产氢以及足够正的价带电势氧化水产氧.需要指出的是,SrTiO3(La,Cr)-SHM样品的导带电势比SrTiO3(La,Cr)-PCM样品的导带电势更负,这意味着前者的导带电势更有利于还原质子产氢.霍尔效应测试的结果表明,两种样品均显示出n型半导体的特征,此外SrTiO3(La,Cr)-SHM样品显示出比SrTiO3(La,Cr)-PCM样品更快的载流子迁移率以及更高的载流子浓度.因此,两种样品不同的导带位置以及不同的载流子迁移率和载流子浓度很可能是造成两者光催化性能具有显著差异的主要原因.

关键词: 钛酸锶, 光催化, 分解水, Z机制, 产氢

Abstract:

The photocatalytic activity of a semiconductor-based photocatalyst largely depends on the semiconductor's intrinsic crystal and electronic properties. We have prepared two types of La and Cr co-doped SrTiO3 photocatalysts (SrTiO3(La,Cr)) using the polymerized complex method (PCM) and sol-gel hydrothermal method (SHM). Under λ > 420-nm visible light irradiation, only the Pt-loaded SrTiO3(La,Cr) prepared by the SHM showed efficient photocatalytic activities for both H2 evolution in the presence of an I- sacrificial reagent and for Z-scheme overall water splitting when it was coupled with the Pt-loaded WO3in the presence of I- and IO3- as the shuttle redox mediator. The superior photocatalytic activity of SrTiO3(La,Cr) prepared by the SHM has been ascribed to its more negative conduction-band position, higher carrier concentration, and higher carrier mobility, demonstrating that the design and synthesis of an H2-evolution photocatalyst with appropriate electronic properties is crucial for achieving Z-scheme overall water splitting.

Key words: Strontium titanate, Photocatalysis, Water splitting, Z-scheme, Hydrogen evolution