物理化学学报 >> 2020, Vol. 36 >> Issue (6): 1905087.doi: 10.3866/PKU.WHXB201905087

所属专题: 热分析动力学和热动力学

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基于光微热量-荧光光谱联用技术研究光催化热力学和动力学的温度效应

覃方红1,万婷2,邱江源1,*(),王一惠1,肖碧源1,黄在银1,3,*()   

  1. 1 广西民族大学化学化工学院,南宁 530008
    2 湖北省地质局第六地质大队,湖北 孝感 432000
    3 广西高校食品安全与药物分析化学重点实验室,南宁 530008
  • 收稿日期:2019-05-31 录用日期:2019-07-17 发布日期:2019-07-19
  • 通讯作者: 邱江源,黄在银 E-mail:gxqiujiangyuan@yeah.net;huangzaiyin@163.com
  • 基金资助:
    国家自然科学基金项目(21873022);国家自然科学基金项目(21573048);广西研究生教育创新计划项目(gxun-chxzs2018062)

Temperature Effects on Photocatalytic Heat Changes and Kinetics via In Situ Photocalorimetry-Fluorescence Spectroscopy

Fanghong Qin1,Ting Wan2,Jiangyuan Qiu1,*(),Yihui Wang1,Biyuan Xiao1,Zaiyin Huang1,3,*()   

  1. 1 College of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning 530008, P. R. China
    2 The Sixth Geological Bureau, Xiaogan 432000, Hubei Province, P. R. China
    3 Guangxi Colleges and Universities Key Laboratory of Food Safety and Pharmaceutical Analytical Chemistry, Nanning 530008, P. R. China
  • Received:2019-05-31 Accepted:2019-07-17 Published:2019-07-19
  • Contact: Jiangyuan Qiu,Zaiyin Huang E-mail:gxqiujiangyuan@yeah.net;huangzaiyin@163.com
  • Supported by:
    the National Natural Science Foundation of China(21873022);the National Natural Science Foundation of China(21573048);Innovation Project of Guangxi Graduate Education, China(gxun-chxzs2018062)

摘要:

利用光微热量-荧光光谱联用技术,对光催化过程的热谱和光谱信息同步监测,获取了五个温度下,g-C3N4@Ag@Ag3PO4光催化降解罗丹明B的原位热动力学、光谱动力学信息,探究了温度对相关参数的影响。结果表明,催化降解反应分为三个阶段:(ⅰ)污染物和催化剂的光响应过程;(ⅱ)光响应吸热和污染物降解放热的竞争过程;(ⅲ)保持稳定的放热率。吸热和放热的竞争过程符合一级动力学,降解速率随着温度的升高而增大;稳定放热阶段为拟零级反应,在283.15 K、288.15 K、293.15 K、298.15 K、303.15 K下的放热速率分别为0.4668 ± 0.3875 μJ∙s−1、0.5314 ± 0.3379 μJ∙s−1、0.5064 ± 0.3234 μJ∙s−1、0.5328 ± 0.3377 μJ∙s−1、0.5762 ± 0.3452 μJ∙s−1。本研究为探究光催化过程的原位热力学、热动力学及光谱信息及机理的推测提供科学依据。

关键词: g-C3N4@Ag@Ag3PO4, 光催化, 光微热量-荧光光谱, 热动力学, 温度效应

Abstract:

The thermodynamics and kinetics of photocatalytic processes provide the scientific foundation for the optimization of reaction conditions and establishment of reaction mechanisms. Because of the limited availability of techniques that can provide in situ thermodynamics coupled with spectral information during photo-driven processes, research regarding the thermodynamics of the photo-driven processes is rare and in-depth studies on their kinetics remain inadequate. Herein, a novel photocalorimetry-fluorescence spectroscopy system composed of a photocalorimeter and laser-induced fluorescence spectrometer based on a 405 nm laser was developed. This system could simultaneously monitor the thermal and spectral information during photocatalytic processes, providing a correlation between nonspecific thermodynamic and specific molecular fluorescence spectral results. A highly efficient, bionic Z-type g-C3N4@Ag@Ag3PO4 nano-composite photocatalyst was developed and characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In situ thermodynamic and spectral kinetic information for Rhodamine B (RhB) degradation on g-C3N4@Ag@Ag3PO4 was obtained at five temperatures by synchronously monitoring the calorimetric and spectrometric results using the newly developed photocalorimetry-fluorescence spectroscopy system and the effects of temperature on various parameters were investigated. The catalytic decomposition comprised three stages at different temperatures: (ⅰ) photoresponse of RhB and photocatalyst, (ⅱ) competition between the endothermic photoresponse and exothermic RhB photodegradation, and (ⅲ) stable exothermic period of RhB photodegradation. The in situ heat flux and fluorescence spectra could be combined to estimate the concentration characteristics of the different photocatalytic reactions: (1) the spectral information suggested that the competitive endothermic and exothermic reactions followed first order kinetics, and the reaction rate constants (k) at five temperatures were calculated. The results also indicated that the degradation rate increased with increasing temperature. The activation energy at each temperature interval was determined, and yielded an average value of 23.82 kJ·mol−1. (2) The calorimetric results revealed that the subsequent stable exothermic period was a pseudo-zero-order process. The exothermic rates at 283.15, 288.15, 293.15, 298.15, and 303.15 K were determined to be 0.4668 ± 0.3875, 0.5314 ± 0.3379, 0.5064 ± 0.3234, 0.5328 ± 0.3377, and 0.5762 ± 0.3452 μJ·s−1, respectively. The novel photocalorimetry-fluorescence spectroscopy technique could concurrently obtain thermodynamic, thermo-kinetic, and molecular spectral information, allowing for the direct correlation of the thermodynamics, thermo-kinetics, and spectrokinetics with the underlying mechanisms of the reaction. This in situ technique integrated the thermal information with spectral information for improved understanding of the microscopic mechanisms of photo-driven processes, providing scientific support for the establishment of photothermal spectroscopy.

Key words: g-C3N4@Ag@Ag3PO4, Photocatalysis, Photocalorimetry-fluorescence spectroscopy, Thermodynamics, Temperature effect

MSC2000: 

  • O642