[论文解读] Effect of Dissolved Oxygen Content on Photocatalytic Performance of Graphene Oxide

M. Bakhtiar Azim, Farzana Nargis+5 more|arXiv (Cornell University)|Jun 18, 2018

Graphene and Nanomaterials Applications参考文献 38被引用 3

一句话总结

本研究探讨了在自然阳光下，氧化石墨烯（GO）光催化降解亚甲蓝（MB）过程中溶解氧（DO）的作用。结果表明，当DO从2.8 mg/L提高到3.9 mg/L时，降解速率常数从0.035 min⁻¹提升至0.062 min⁻¹，H₂O₂辅助的GO在60分钟内实现了92%的脱色率，归因于自由基生成和电子转移效率的提升。

ABSTRACT

Graphene, a two-dimensional (2D) promising emergent photocatalyst consisting of earth-abundant elements. This study evaluated the potential of graphene oxide (GO) towards photocatalytic degradation of a novel organic dye, Methylene Blue (MB). In this work, photocatalytic activity of graphene oxide (GO), graphene oxide (GO) along with hydrogen peroxide (H2O2) were tested by photodegrading Methylene Blue (MB) in aqueous solution. The resulted GO nanoparticles were characterized by X-ray powder diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Fourier Transform Infrared Ray Spectroscopy. The XRD data confirms the sharp peak centered at 2Theta=10.44 degree corresponding to (002) reflection of GO. Based on our results, it was found that the resulted GO nanoparticles along with H2O2 achieved ~92% photodecolorization of MB compared to ~63% for H2O2 under natural sunlight irradiation at pH~7 in 60 min. The influences of oxygen and hydrogen peroxide (H2O2) on the degradation of MB during sunlight/GO process were investigated. Experimental results indicated that oxygen was a determining parameter for promoting the photocatalytic degradation. The rate constant of degradation (k1) increased from 0.019 to 0.042 per minute for dissolved oxygen content (DOC) 3.5 mg/L when direct photocatalysis (MB/GO) and H2O2-assisted photocatalysis (MB/H2O2/GO) were used. Owing to the fact that H2O2 acted as an electron and hydroxyl radicals scavenger, the addition of H2O2 should in a proper dosage to enhance the degradation of MB. Moreover, as the initial concentration of dissolved oxygen (DO) was increased from 2.8 to 3.9 mg/L, the rate constant of degradation (k1) increased from 0.035 to 0.062 per minute. The mechanism of photodegradation and kinetics were also studied for both direct photocatalysis and H2O2-assisted photocatalysis.

研究动机与目标

• 评估氧化石墨烯（GO）在自然阳光下降解亚甲蓝（MB）的光催化性能。
• 研究溶解氧（DO）对GO介导的MB降解效率的影响。
• 考察过氧化氢（H₂O₂）与GO的协同效应，以增强光催化活性。
• 阐明在不同DO和H₂O₂条件下反应动力学及降解机理。

提出的方法

• 通过改进的Hummer法合成GO纳米颗粒，并利用XRD、SEM、EDS和FTIR进行表征。
• 在pH≈7的自然阳光照射下，进行直接光催化（MB/GO）和H₂O₂辅助光催化（MB/H₂O₂/GO）实验。
• 将溶解氧（DO）浓度从2.8 mg/L调节至3.9 mg/L，以评估其对降解动力学的影响。
• 测量MB随时间的光脱色效率，并计算降解动力学的速率常数（k1）。
• 通过动力学模型和H₂O₂的自由基捕获效应分析反应路径。
• 使用XRD确认在2θ = 10.44°处出现(002)衍射峰，表明GO合成成功。

实验结果

研究问题

• RQ1 溶解氧（DO）浓度如何影响使用GO降解亚甲蓝（MB）的光催化降解速率？
• RQ2 过氧化氢（H₂O₂）在增强GO对MB降解的光催化效率中起什么作用？
• RQ3 在MB/GO和MB/H₂O₂/GO体系中，随着DO浓度升高，降解速率常数（k1）如何变化？
• RQ4 H₂O₂和DO共同作用下降解性能增强的机理是什么？
• RQ5 在相同条件下，直接光催化与H₂O₂辅助光催化的动力学曲线有何差异？

主要发现

• 在自然阳光下，向GO中添加H₂O₂使MB光脱色率从约63%（仅GO）提升至约92%（60分钟内）。
• 在DO浓度为3.5 mg/L时，降解速率常数（k1）从仅GO的0.019 min⁻¹提升至H₂O₂/GO体系的0.042 min⁻¹。
• 在H₂O₂辅助体系中，将DO从2.8 mg/L提高到3.9 mg/L，使速率常数从0.035 min⁻¹提升至0.062 min⁻¹。
• 氧气被确定为促进光催化降解的关键因素，可能通过促进电子转移和自由基生成实现。
• H₂O₂既作为电子受体，又作为羟基自由基的来源，但需优化用量以避免捕获有益自由基。
• XRD确认GO存在，其在2θ = 10.44°处出现尖锐的(002)峰，表明成功合成二维氧化物结构。