鎢基材摻硼鑽石電極製備及用於電化學降解水中法莫替丁

Boron-doped diamond on tungsten electrodes for electrochemical degradation of famotidine in water

黃泰鄅(Huang Tai-Yu)

指導教授 ： 黃國林 ； 趙浩然

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2022年)

https://doi.org/10.6346/NPUST202200286

摘要

摻硼鑽石(boron-doped diamond，BDD)是一款優良的電極材料，適用於電化學降解廢水中有機污染物。本研究是利用鎢(W)板作為基材，採用熱燈絲化學氣相沉積法(hot filament chemical vapor deposition, HFCVD)鍍覆BDD薄膜，製備W/BDD電極，應用於電化學降解法莫替丁(Famotidine)有機污染物，並與商用Neocoat及Diachem電極比較。研究結果顯示，氣體導入硼/碳比(B/C) 0.25%、B/C 0.50%及B/C 0.75% BDD電極之析氧電位分別為2.20、2.25及2.35 V vs. Ag/AgCl，而Neocoat及Diachem的析氧電位分別為2.30及2.10 V vs. Ag/AgCl。在循環伏安(CV)掃描時，自製與商用BDD電極皆有硫酸鹽被氧化為過硫酸鹽之氧化峰。再者，法莫替丁於B/C 0.25%電極上之氧化峰出現在1.0 V vs. Ag/AgCl，而對應之還原峰出現在-1.5 V vs. Ag/AgCl。因此，法莫替丁可在此BDD電極上進行直接電氧化降解。
利用拉曼(Raman)光譜儀與X射線光電子能譜儀(X-ray photoelectron spectroscopy，XPS)進行W/BDD表面分析的研究結果顯示，硼原子已摻入鑽石結構當中。導入氣體硼碳比B/C 0.25%、0.50%及0.75%製備的BDD薄膜，實測B/C分別為0.1%、0.3%及0.2%，而B原子濃度分別為1.01×1021、2.17×1021及4.47×1021 cm-3。FE-SEM分析B/C 0.25%、0.5%及0.75% BDD電極所得之鑽石平均粒徑分別為256 nm、231 nm及36 nm，而XRD分析所得微晶尺寸(crystallite size)分別為29 nm、14 nm及22 nm。摻硼量的增加使鑽石的晶粒尺寸變小並使TOC降解效率下降(B/C 0.25% > B/C 0.5% > B/C 0.75%)，但此三支BDD電極降解法莫替丁的效能相似。
使用硫酸鈉為電解質所得之TOC降解效率較使用氯化鈉為佳，但pH及電解質濃度對法莫替丁及TOC降解效率之影響較不明顯。法莫替丁電降解較佳操作條件為25°C、pH 7、0.1 M硫酸鈉及B/C 0.25% BDD陽極。以5,5-二甲基-1-吡咯啉 N-氧化物(DMPO)氫氧自由基捕捉劑，在電流密度0.03 A/cm2下於H2SO4溶液中進行ESR試驗，結果顯示為B/C 0.25% BDD電極在5分鐘時的DMPO-OH強度為三支自製電極中最高。依據UV-Vis分析結果，法莫替丁在波長265 nm有吸收峰，在較佳實驗條件下用自製B/C 0.25% BDD電極降解法莫替丁，隨電解時間增加，其強度逐漸降解至ND (240 min)，而B/C 0.25% BDD電極對法莫替丁之降解效能與商用電極相似。
LC-MS分析結果顯示，在電化學降解時，法莫替丁直鏈S首先被氧化或氫氧自由基攻擊(m/z = 356) (接上O)，接著氧化攻擊支鏈C-N (m/z = 370) (接上O或OH) (圖4-25B)，然後使其在C-S處裂解為m/z = 171及173 (圖4-26)並接上O或OH。這些中間產物可能被繼續氧化形成有機酸，經由逐步氧化降解，最後礦化成CO2、H2O及NO3-。

關鍵字

法莫替丁 ； 電化學降解 ； 熱燈絲化學氣相沉積 ； 鎢基材摻硼鑽石電極 ； X光繞射分析 ； 場發射掃描式電子顯微鏡 ； 拉曼光譜 ； X射線電子能譜 ； 電子自旋共振 ； 高效液相層析 ； 紫外-可見光光度分析 ； 自由基

並列摘要

Boron-doped diamond (BDD) is an excellent anode material for electrochemical degradation of organic pollutants in water/wastewater. In this study, tungsten (W) plates were used as the substrate and a hot filament chemical gas deposition (HFCVD) method was adopted to prepare W/BDD electrodes for electrochemical degradation of famotidine (an emerging contaminant) in aqueous solutions. Two commercial BDD electrodes (NeoCoat and Diachem) were also tested for comparison. The results showed that the oxygen evolution potentials (OEPs) of lab-made B/C 0.25%, B/C 0.50%, and B/C 0.75% BDD electrodes were 2.20, 2.25, and 2.35 V vs. Ag/AgCl, respectively, while those of NeoCoat and Diachem were 2.30 and 2.10 V vs. Ag/AgCl, respectively. In (cyclic voltammetry, CV) analysis using the B/C 0.25% BDD electrode, the famotidine oxidation peak appeared at 1.0 V vs. Ag/AgCl, with a corresponding reduction peak at -1.5 V vs. Ag/AgCl; therefore, famotidine can be directly oxidized (diffusion control) on the B/C 0.25% BDD. Moreover, the peaks of sulfate oxidation to persulfate were also observed on the lab-made and commercial BDD electrodes.
The surface analyses of lab-made BDD films using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) showed that the boron atoms had doped into diamond structure. The BDD films prepared by introducing the boron to carbon gas ratios (B/C) of 0.25%, 0.50%, and 0.75% showed experimentally measured B/C values of 0.1%, 0.3% and 0.2%, respectively, with corresponding B atomic concentration of 1.01×1021, 2.17×1021 and 4.47×1021 cm-3, respectively. The analysis of field emission scanning electron microscope (FE-SEM) for B/C 0.25%, 0.5% and 0.75% BDD electrodes showed their average diamond particle sizes of 256, 231, and 36 nm, respectively, although the crystallite sizes obtained from X-ray diffraction (XRD) analysis were 29, 14, and 22 nm, respectively. The increase in boron doping concentration reduced the size of diamond grain and TOC degradation efficiency (B/C 0.25% > B/C 0.5% > B/C 0.75%), although these three lab-made BDD electrodes presented similar performance on the electrochemical degradation of famotidine.
The TOC degradation efficiency was better in sodium sulfate solution than in sodium chloride solution, while initial pH and electrolyte concentration did not significantly affect the degradation efficiencies of famotidine and TOC. The better experimental operating conditions obtained in this study were 25°C, pH 7, 0.1 M Na2SO4 electrolyte, and B/C 0.25% BDD anode. The ESR analysis performed in H2SO4 solution at 0.03 A/cm2 showed that the DMPO-•OH strength of the B/C 0.25% BDD electrode exhibited the highest DMPO-•OH signal intensity at 5 min among the three lab-made BDD electrodes. Under the better experimental conditions using the B/C 0.25% BDD anode, the absorbance at 265 nm in UV-Vis analysis gradually decreased to ND during the electrolysis of famotidine for 240-min, while the degradation efficiency of famotidine for the B/C 0.25% BDD anode was comparable to those of the two commercial BDD electrodes.
According to LC-MS analysis, the electrochemical degradation of famotidine firstly underwent the oxidation/hydroxyl radical attack of straight chain S (m/z = 356) (formation of S=O), followed by chain end NH2 oxidation to NHOH (m/z = 370). Then its straight chain C-S bond broke to form two fragments and they were oxidized to m/z = 171 (with an O end) and 173 (with an OH end). It is also possible that the straight chain end C (bonded to N) or ring chain C (bonded to S) of famotidine might be oxidized by hydroxylation (m/z = 357). These intermediates were further oxidized to form organic acids which finally mineralized into CO2, H2O, and NO3-
.

並列關鍵字

Famotidine ； Electrochemical Degradation ； Hot-Filament Chemical Vapor Deposition (HFCVD) ； Boron-Doped Diamond (BDD) electrode on Tungsten ； X-ray Diffraction (XRD) ； Field Emission Scanning Electron Microscope (FE-SEM) ； Raman spectroscopy ； X-ray photoelectron spectroscopy (XPS) ； electron spin resonance (ESR) ； Radical ； High-Performance Liquid Chromatography (HPLC) ； UV-Vis spectrometer

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