本文選題：過鈍化　切入點：電催化氧化　出處：《中國礦業(yè)大學(xué)》2017年碩士論文

【摘要】：本文運用循環(huán)伏安法和恒電位法對鉑電極過鈍化區(qū)域中硫化鈉電催化氧化動力學(xué)進(jìn)行研究,并對反應(yīng)過程中的串聯(lián)外阻效應(yīng)、硫化鈉濃度效應(yīng)和氯離子效應(yīng)進(jìn)行探討;用CCD攝像機實時監(jiān)測電極表面,觀察到豐富的時空斑圖;利用高效液相色譜法檢測反應(yīng)過程中產(chǎn)生的物種,提出振蕩機理;利用KarhunenLoeve分解分析時空斑圖。首先討論了串聯(lián)外阻和硫化鈉濃度對電化學(xué)振蕩的影響。雙電層電勢作為自催化變量促進(jìn)鉑氧化物的生成,產(chǎn)生負(fù)微分阻抗,串聯(lián)外阻促進(jìn)雙電層電勢增大加強體系的正反饋,硫離子作為消耗鉑氧化物的物種是體系的負(fù)反饋。當(dāng)體系中正負(fù)反饋作用有滯后環(huán),即硫化鈉濃度為1.50 mol/L,串聯(lián)外阻為300?時,在過鈍化區(qū)域觀察到大幅振蕩與小幅振蕩共存的HN-NDR振蕩,大幅振蕩對應(yīng)硫沉積與溶解的協(xié)同化。氯離子的引入對體系的不穩(wěn)定性特征有顯著影響。一方面,氯離子作為金屬電極化學(xué)吸附物種引入一個新的正反饋;另一方面,高濃度氯離子對鉑氧化物的溶解帶來體系的負(fù)反饋。當(dāng)氯離子濃度較低時,氯離子引起的吸附正反饋效應(yīng)較小,對過鈍化區(qū)域的振蕩影響不大;隨著氯離子濃度的增大,氯離子的化學(xué)吸附增強,與硫離子消耗鉑氧化物的負(fù)反饋相互作用,加強過鈍化區(qū)域的振蕩;當(dāng)氯離子濃度過大時,氯離子溶解鉑氧化物的負(fù)反饋為主,正反饋逐漸消失,使得振蕩衰減,直至消失。除協(xié)同化現(xiàn)象外,在過鈍化區(qū)域的小幅振蕩區(qū)域還能觀察到螺旋波、閃爍波、前沿波和條紋移動斑圖。用恒電位法研究體系過鈍化區(qū)域的振蕩演化過程,振蕩電勢區(qū)域變寬且負(fù)移,在小幅振蕩區(qū)域觀察到呼吸波結(jié)構(gòu),在小幅與大幅振蕩共存時觀察到呼吸波與協(xié)同化的交替。用Karhunen-Loeve(KL)分解時空斑圖得到呼吸波有多種模式,能量的百分比較低,而呼吸波與協(xié)同化的交替波可以通過一種主要的模式表示。
[Abstract]:In this paper, the kinetics of electrocatalytic oxidation of sodium sulfide in the region of platinum electrode overpassivation was studied by cyclic voltammetry and potentiostatic method. The series resistance effect, concentration effect of sodium sulfide and chloride ion effect in the reaction process were discussed.The CCD camera was used to monitor the electrode surface in real time, and abundant spatiotemporal patterns were observed. The species produced in the reaction were detected by high performance liquid chromatography (HPLC), and the oscillation mechanism was proposed. The KarhunenLoeve decomposition was used to analyze the spatio-temporal pattern.The effects of series resistance and sodium sulfide concentration on electrochemical oscillation were discussed.The double layer potential is used as the autocatalytic variable to promote the formation of platinum oxide, resulting in negative differential impedance. The series resistance promotes the increase of the potential of the double layer to increase the positive feedback of the enhanced system. The sulfur ion as the species consuming platinum oxide is the negative feedback of the system.When the positive and negative feedback in the system has hysteresis ring, that is, the concentration of sodium sulfide is 1.50 mol / L, the series resistance is 300?HN-NDR oscillations coexisting with large oscillations and small oscillations were observed in the over-passivation region, and the large oscillations corresponded to the synergism of sulfur deposition and dissolution.The introduction of chloride ions has a significant effect on the instability characteristics of the system.On the one hand, chloride ion as a chemisorbed species of metal electrode introduces a new positive feedback; on the other hand, the solution of platinum oxide with high concentration of chloride ion brings negative feedback to the system.When the concentration of chloride ion is low, the positive feedback effect of adsorption induced by chlorine ion is small, and the oscillation of the over-passivating region is not affected, and the chemisorption of chloride ion increases with the increase of chloride ion concentration.When the concentration of chlorine ion is too high, the negative feedback of dissolved platinum oxide is dominant, and the positive feedback gradually disappears, which makes the oscillation attenuate until it disappears.In addition to synergetic phenomena, spiral waves, scintillation waves, front waves and fringe movementpatterns can also be observed in the small oscillation region of the passivation region.The oscillatory evolution of the over-passivation region of the system is studied by means of the potentiostatic method. The oscillatory potential region becomes wider and negative. The structure of the respiratory wave is observed in the small oscillation region, and the alternations between the respiration wave and the synergism are observed at the coexistence of the small and large oscillations.Using Karhunen-Loevegne KL) to decompose the spatiotemporal pattern, it is found that there are many modes of respiratory wave, and the percentage of energy is low, and the alternate wave of respiration wave and synergetic wave can be expressed by one main mode.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O646.54

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 ;Current oscillations during the electrochemical oxidation of sulfide in the presence of an external resistor[J];Science in China(Series B:Chemistry);2008年04期

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本文編號：1719303