阳极TiO2/g-C3N4与阴极WO3/W纳米催化剂之间扩大的异质结自偏压系统去除污染物

引用本文: 于婷婷, 柳丽芬, 杨凤林. 阳极TiO₂/g-C₃N₄与阴极WO₃/W纳米催化剂之间扩大的异质结自偏压系统去除污染物[J]. 催化学报, 2017, 38(2): 270-277. doi: 10.1016/S1872-2067(16)62556-1 shu

Citation: Tingting Yu, Lifen Liu, Fenglin Yang. Heterojunction between anodic TiO₂/g-C₃N₄ and cathodic WO₃/W nano-catalysts for coupled pollutant removal in a self-biased system[J]. Chinese Journal of Catalysis, 2017, 38(2): 270-277. doi: 10.1016/S1872-2067(16)62556-1 shu

阳极TiO₂/g-C₃N₄与阴极WO₃/W纳米催化剂之间扩大的异质结自偏压系统去除污染物

a 大连理工大学环境学院工业生态与环境工程教育部重点实验室, 辽宁大连 116024;
b 大连理工大学食品与环境学院, 辽宁盘锦 124221
基金项目:
国家自然科学基金（21177018，21677025）；高等学校学科创新引智计划（111计划，B13012）.

摘要: 电化学或光电化学半导体催化剂广泛应用于降解污水中的有机与无机污染物，有望实现低能耗且高效的污染物降解.目前，已有多种异质结半导体光催化剂的研究报道，并且大多数的研究结果显示催化剂活性有明显提高，但仍存在着光激发后电子与空穴的复合问题.光电化学系统的构建可减少电子与空穴的复合，因光催化阳极与光催化阴极之间费米能级的不同，在两极之间形成异质结，产生内电场，自生偏压驱动电子流动.已有诸多研究报道将TiO₂催化剂与g-C₃N₄复合形成异质结，提高光催化活性.由于g-C₃N₄（~-1.12 eV vs.NHE）导带位置相比于TiO₂（~-0.2 eV vs.NHE）更负，因此在两者之间可形成内部偏压，驱动电子由g-C₃N₄转移至TiO₂.WO₃/W导带位置（~+0.2 eV vs.NHE）比TiO₂与g-C₃N₄更正，因此自生内偏压促进电子由阳极流动至阴极.
我们研究组发展了一种在无光条件下的自偏压电化学燃料电池系统，异质结间的电子流动可活化氧气产生自由基，自由基可用于阳极污染物的降解，但阴极未降解污染物.本文在上述研究基础上，应用TiO₂/g-C₃N₄异质结与WO₃/W分别作为阳极与阴极催化剂，构建自偏压催化燃料电池系统，在无光条件下催化阳极与阴极之间自发电子转移，活化氧气产生自由基，同时实现低能耗阳极室内污染物如罗丹明B和三氯生的氧化，且电子用于阴极室内硝态氮的还原.
通过在空气中原位加热与氧化钨丝制得WO₃/W阴极，由扫描电镜图可知在钨丝表面形成三氧化钨纳米粒子，此结构增大了催化剂的表面积以及催化剂与电解液的接触面积，有利于电荷转移.用循环伏安曲线（CV）与电流时间曲线（I-t）表征了电极的电化学性质.CV测试结果表明，相比于硫酸钠电解液，WO₃/W阴极在含有硝态氮的电解液中存在还原峰，且紫外照射比无光条件下的电流略大，说明此电极在无光条件下可用于还原硝态氮，有光更利于激发催化剂产生电子与空穴降解和去除污染物.在硫酸钠电解液中，无光照条件下（同室），I-t曲线表明TiO₂/g-C₃N₄相比于WO₃/W电极可产生更大电流，因此选择TiO₂/g-C₃N₄作为阳极，WO₃/W作为阴极.在含污染物电解液中，无光照条件下，Pt片作为对电极时（同室），I-t曲线中的电流在曝气时比未曝气时小，说明电极上产生的部分电子用于活化氧气产生自由基，因此转移到外电路的电子减少，电流变小；相反，当TiO₂/g-C₃N₄阳极置于阳极室，WO₃/W阴极置于阴极室时（两室），阳极鼓入空气，阴极曝氮气时，电流比两室均未曝气时大，说明此系统有利于电子产生与转移，用于氧化还原去除污染物.相比于传统方法，此系统通过阳极室内曝空气与活化分子氧形成自由基，无需外加偏压，在有光与无光条件下，均可实现对阳极室与阴极室内不同污染物的同时去除或降解，同时提出了此系统中的降解机理.

关键词:

English

Heterojunction between anodic TiO₂/g-C₃N₄ and cathodic WO₃/W nano-catalysts for coupled pollutant removal in a self-biased system

a Key Laboratory of Industrial Ecology and Environmental Engineering, MOE, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, Liaoning, China;
b School of Food and Environment, Dalian University of Technology, Panjin 124221, Liaoning, China
Received Date: 23 July 2016
Revised Date: 02 September 2016
Available Online: 02 March 2017
Fund Project:
This work was supported by the National Natural Science Foundation of China (21177018, 21677025) and the Program of Introducing Talents of Discipline to Universities (B13012).

Abstract: An anodic TiO₂/g-C₃N₄ hetero-junction and cathodic WO₃/W were used to build a self-sustained catalytic fuel cell system for oxidizing rhodamine B or triclosan and reducing NO₃^--N to N₂ simultaneously. The WO₃ nano-catalyst was formed in situ by heating and oxidizing a tungsten wire in air. Cyclic voltammetry and current-time curves were used to characterize the electrochemical properties of the electrodes and system. Aeration and activation of molecular oxygen by self-biased TiO₂/g-C₃N₄ led to the formation of reactive oxidizing species in the fuel cell. The mechanism of simultaneous anodic oxidation of pollutants and cathodic reduction of nitrate was proposed. The spontaneously formed circuit and tiny current were used simultaneously in treating two kinds of wastewater in the reactor chambers, even without light illumination or an external applied voltage. This new catalytic pollution control route can lower energy consumption and degrade many other kinds of pollutants.

Key words:

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阳极TiO₂/g-C₃N₄与阴极WO₃/W纳米催化剂之间扩大的异质结自偏压系统去除污染物

English

Heterojunction between anodic TiO₂/g-C₃N₄ and cathodic WO₃/W nano-catalysts for coupled pollutant removal in a self-biased system

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