g-C_3N_4@Ag_3PO_4光催化降解罗丹明B过程的原位光-微热量-荧光光谱研究

采用光-微热量-荧光光谱联用系统获取了g-C_3N_4@Ag_3PO_4光降解罗丹明B(RhB)的原位热/动力学信息和三维荧光光谱信息,并结合热力学和光谱学结果探究了光催化降解罗丹明B的微观机制.结果表明,光催化降解过程主要分为表观吸热、热平衡以及稳定放热3个阶段.在g-C_3N_4@Ag_3PO_4存在下,可见光照射10 min后,罗丹明B的三维荧光特征发射峰强度降低至初始值的7.1%,罗丹明B的降解脱色率达92.9%,是相同条件下以纯g-C_3N_4为催化剂时的2.06倍.随着光照时间的延长,光-微热量计显示10 min后以降解及矿化非荧光中间产物为主,并保持热焓变化率为-(0.226±0.0916)mJ/s稳定放热,为拟零级反应过程,并且该阶段为光催化反应的决速步骤.

In-situ Photocatalytic Process of Rhodamine B over g-C3N4@Ag3PO4 Nanocomposites Based on Photomicrocalorimeter-fluorescence Spectrometry

A photomicrocalorimeter-fluorescence spectrometer was applied to obtain in-situ thermodynamics, kinetics and 3D fluorescence spectra of Rhodamine B photocatalysis over g-C3N4 @ Ag3PO4 nanocomposites. And its mechanism was investigated by coupling the thermodynamics and its spectroscopic information. Consequently, the whole process underwent an initial endothermic reaction and a subsequent exothermic stage, and finally maintained a stable exothermic platform. The intensity of fluorescence emission peak of Rhodamine B over g-C3N4 @ Ag3PO4 decreased sharply within the illumination of 10 min, its degradation rate reached 92. 9%, which was 2. 06 times that over g-C3N4 . Subsequently, the photodegradation of the ring and intermediates without fluorescent chromophores were dominated, which maintained a stable exothermic rate of-(0. 226±0. 0916) mJ/ s with a pseudo-zero order process. This process was the rate-determining step. Therefore, Rhodamine B photocatalysis was a pseudo-zero-order process rather than a first order process.