催化学报

催化学报 ›› 2020, Vol. 41 ›› Issue (1): 9-20.DOI: 10.1016/S1872-2067(19)63382-6

• 光催化产氢 • 上一篇    下一篇

石墨烯修饰三氧化钨/二氧化钛S型异质结增强的光催化产氢活性

何菲a, 孟爱云a, 程蓓a, Wingkei Hob, 余家国a,c   

  1. a 武汉理工大学材料复合新技术国家重点实验室, 材料科学与工程国际化示范学院, 湖北武汉 430070, 中国;
    b 香港教育大学科学与环境学系, 海洋污染国家重点实验室, 香港, 中国;
    c 沙特阿卜杜勒阿齐兹国王大学科学部物理系, 吉达 21589, 沙特阿拉伯
  • 收稿日期:2019-02-28 修回日期:2019-04-16 出版日期:2020-01-18 发布日期:2019-10-22
  • 通讯作者: 余家国, Wingkei Ho
  • 基金资助:
    国家自然科学基金（U1705251，21871217，21573170，21433007）；国家重点研发计划项目（2018YFB1502001）.

Enhanced photocatalytic H2-production activity of WO3/TiO2 step-scheme heterojunction by graphene modification

Fei Hea, Aiyun Menga, Bei Chenga, Wingkei Hob, Jiaguo Yua,c   

  1. a State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, Hubei, China;
    b Department of Science and Environmental Studies and State Key Laboratory in Marine Pollution, The Education University of Hong Kong, Tai Po, N. T. Hong Kong, China;
    c Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
  • Received:2019-02-28 Revised:2019-04-16 Online:2020-01-18 Published:2019-10-22
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (U1705251, 21871217, 21573170, 21433007) and the National Key Research and Development Program of China (2018YFB1502001).

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摘要： 太阳光驱动的光催化分解水产氢是利用太阳能解决当前能源危机和环境问题的理想策略.二氧化钛由于其稳定、环境友好和成本低等优点受到广泛研究，在光催化领域具有不可或缺的作用.然而，纯二氧化钛光催化剂具有光生电子-空穴复合率高、太阳能利用率低等缺点，使其在光催化产氢领域的应用受到限制.迄今为止，人们探索了多种改性策略来提高二氧化钛的光催化活性，如贵金属负载、金属或非金属元素掺杂、构建异质结等.
通过复合两个具有合适能带排布的半导体来构建异质结可以大大提高光生载流子的分离，被认为是一种有效的解决方案.最近提出了一种新的S型异质结概念，以解释不同半导体异质界面载流子转移分离的问题.S型异质结是在传统Ⅱ型和Z型（液相Z型、全固态Z型、间接Z型、直接Z型）基础上提出的，但又扬长避短，优于传统Ⅱ型和Z型.通常，S型异质结是由功函数较小、费米能级较高的还原型半导体光催化剂和功函数较大、费米能级较低的氧化型半导体光催化剂构建而成.三氧化钨禁带宽度较小（2.4-2.8eV），功函数较大，是典型的氧化型光催化剂，也是构建S型异质结的理想半导体光催化剂.根据S型电荷转移机制，三氧化钨/二氧化钛复合物在光辐照下，三氧化钨导带上相对无用的电子与二氧化钛价带上相对无用的空穴复合，二氧化钛导带上还原能力较强的电子和三氧化钨价带上氧化能力较强的空穴得以保留，从而在异质界面上实现了氧化还原能力较强的光生电子-空穴对的分离.同时，石墨烯作为一种蜂窝状碳原子二维材料，是理想的电子受体，在异质结光催化剂中能及时转移电子.而且，石墨烯具有较好的导热性和电子迁移率，光吸收强，比表面积大，可为光催化反应提供丰富的吸附和活性位点，已经被认为是一种重要催化剂载体和光电分解水产氢的有效共催化剂.
本文采用简便的一步水热法制备石墨烯修饰的三氧化钨/二氧化钛S型异质结光催化剂.光催化产氢性能测试表明，三氧化钨/二氧化钛/石墨烯复合材料的光催化产氢速率显著提高（245.8 μmol g-1 h-1），约为纯TiO2的3.5倍.高分辨透射电子显微镜、拉曼光谱和X射线光电子能谱结果证明了TiO2和WO3纳米颗粒的紧密接触，并成功负载在还原氧化石墨烯（rGO）上.X射线光电子能谱中Ti 2p结合能的增加证实TiO2和WO3之间强的相互作用和S型异质结的形成.此外，复合材料中的rGO大大拓展了复合物的光吸收范围（紫外-可见漫反射光谱），增强了光热转换效应，而且rGO与TiO2之间形成肖特基结，促进了TiO2导带电子的转移和分离.总之，WO3和TiO2的S型异质结与TiO2和rGO之间的肖特基异质结的协同效应抑制了相对有用的电子和空穴的复合，有利于氧化还原能力较强的载流子的分离和进一步转移，加速了表面产氢动力学，于是增强了三元复合光催化剂的光催化产氢活性.

关键词: 像梯形的异质结, S型异质结, S异质结, 光催化剂, 光解水产氢

Abstract: Sunlight-driven photocatalytic water-splitting for hydrogen (H2) evolution is a desirable strategy to utilize solar energy. However, this strategy is restricted by insufficient light harvesting and high photogenerated electron-hole recombination rates of TiO2-based photocatalysts. Here, a graphene-modified WO3/TiO2 step-scheme heterojunction (S-scheme heterojunction) composite photocatalyst was fabricated by a facile one-step hydrothermal method. In the ternary composite, TiO2 and WO3 nanoparticles adhered closely to reduced graphene oxide (rGO) and formed a novel S-scheme heterojunction. Moreover, rGO in the composite not only supplied abundant adsorption and catalytically active sites as an ideal support but also promoted electron separation and transfer from the conduction band of TiO2 by forming a Schottky junction between TiO2 and rGO. The positive cooperative effect of the S-scheme heterojunction formed between WO3 and TiO2 and the Schottky heterojunction formed between TiO2 and graphene sheets suppressed the recombination of relatively useful electrons and holes. This effect also enhanced the light harvesting and promoted the reduction reaction at the active sites. Thus, the novel ternary WO3/TiO2/rGO composite demonstrated a remarkably enhanced photocatalytic H2 evolution rate of 245.8 μmol g-1 h-1, which was approximately 3.5-fold that of pure TiO2. This work not only presents a low-cost graphene-based S-scheme heterojunction photocatalyst that was obtained via a feasible one-step hydrothermal approach to realize highly efficient H2 generation without using noble metals, but also provides new insights into the design of novel heterojunction photocatalysts.

Key words: Step-like heterojunction, S-scheme heterojunction, S heterojunction, Photocatalyst, Hydrogen generation