利用有机助剂提高TiO_2光催化产氢和降解性能（英文）
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摘要
采用助催化剂加速光催化材料中空穴-电子对的分离提高光催化效率的有效方法.本文以有机分子草酰胺(OA)作为新型助催化剂来促进TiO2光催化材料的光生载流子分离,从而增强其光催化H2释放和染料降解性能.最佳TiO2-OA复合光催化剂上H2的析出和罗丹明B的光催化效率分别达到2371μmol g–1 h–1和1.43×10–2 min–1,分别是TiO2的2.4和3.8倍.系统研究了光催化增强的可能机理,并提出OA凭借其π-共轭结构作为助催化剂,不仅增强了TiO2的光吸收,而且促进了空穴转移,因而达到了加速电荷分离的效果.利用湿化学法合成了TiO2-OA光催化材料,并采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、红外光谱(FT-IR)以及紫外-可见漫反射光谱(UV-vis)等表征方法对该催化剂的结构特征、微观形貌和光学性能进行分析,并研究了TiO2-OA复合材料的光催化性能. SEM和TEM结果表明, TiO2-OA呈方形,尺寸约为30nm.OA含量为30wt%的TiO2-OA样品在用于制氢的光催化水分解反应中表现最佳.同时研究了TiO2-OA光催化剂的光催化机理,用对苯醌、乙二胺四乙酸二钠和正丁醇进行了自由基捕捉剂实验.结果表明,羟基自由基在降解有机染料过程中起主要作用.通过光电流测试、材料价带导带位置计算以及·O2和·OH定量实验并结合文献分析认为,掺入具有独特π-共轭结构的OA可以提供空穴转移位点,从而极大地促进TiO2和OA之间光生电子-空穴的分离和转移.本工作可能为构建具有新型有机助催化剂的高效光催化体系开辟了一条新途径.
Accelerating the separation efficiency of photoexcited electron-hole pairs with the help of highly active co-catalysts has proven to be a promising approach for improving photocatalytic activity. Thus far, the most developed co-catalysts for semiconductor-based photocatalysis are inorganic materials; the employment of a specific organic molecule as a co-catalyst for photocatalytic hydrogen evolution and pollutant photodegradation is rare and still remains a challenging task. Herein, we report on the use of an organic molecule, oxamide(OA), as a novel co-catalyst to enhance electron-hole separation, photocatalytic H_2 evolution, and dye degradation over TiO_2 nanosheets. OA-modified TiO_2 samples were prepared by a wet chemical route and demonstrated improved light absorption in the visible-light region and more efficient charge transport. The photocatalytic performance of H_2 evolution from water splitting and rhodamine B(RhB) degradation for an optimal OA-modified TiO_2 photocatalyst reached 2.37 mmol g~(-1) h~(-1) and 1.43×10-2 min~(-1), respectively, which were 2.4 and 3.8 times higher than those of pristine TiO_2, respectively. A possible mechanism is proposed, in which the specific π-conjugated structure of OA is suggested to play a key role in the enhancement of the charge transfer and catalytic capability of TiO_2. This work may provide advanced insight into the development of a variety of metal-free organic molecules as functional co-catalysts for improved solar-to-fuel conversion and environmental remediation.
Accelerating the separation efficiency of photoexcited electron-hole pairs with the help of highly active co-catalysts has proven to be a promising approach for improving photocatalytic activity. Thus far, the most developed co-catalysts for semiconductor-based photocatalysis are inorganic materials; the employment of a specific organic molecule as a co-catalyst for photocatalytic hydrogen evolution and pollutant photodegradation is rare and still remains a challenging task. Herein, we report on the use of an organic molecule, oxamide(OA), as a novel co-catalyst to enhance electron-hole separation, photocatalytic H_2 evolution, and dye degradation over TiO_2 nanosheets. OA-modified TiO_2 samples were prepared by a wet chemical route and demonstrated improved light absorption in the visible-light region and more efficient charge transport. The photocatalytic performance of H_2 evolution from water splitting and rhodamine B(RhB) degradation for an optimal OA-modified TiO_2 photocatalyst reached 2.37 mmol g~(-1) h~(-1) and 1.43×10-2 min~(-1), respectively, which were 2.4 and 3.8 times higher than those of pristine TiO_2, respectively. A possible mechanism is proposed, in which the specific π-conjugated structure of OA is suggested to play a key role in the enhancement of the charge transfer and catalytic capability of TiO_2. This work may provide advanced insight into the development of a variety of metal-free organic molecules as functional co-catalysts for improved solar-to-fuel conversion and environmental remediation.
引文
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