Pt(100)修飾鉛對甲酸氧化活性探討

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/94674

Title:	Pt(100)修飾鉛對甲酸氧化活性探討
Authors:	昌承燁;Chang, Cheng-Yeh
Contributors:	化學學系
Keywords:	白金(100);鉛修飾白金(100);甲酸氧化;Pt(100);Pb-modified Pt(100);Formic Acid oxidation
Date:	2024-07-22
Issue Date:	2024-10-09 15:23:09 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究透過循環伏安法(Cyclic Voltammetry，CV)和掃描式電子穿隧顯微鏡(Scanning Tunneling Microscope，STM)，探討鉛修飾於Pt(100)電極表面上的結構及對甲酸氧化反應催化效果，實驗首先討論單層鉛沉積、多層鉛沉積與鉛鉑合金結構，並分別針對甲酸分子氧化活性與電位變化進行探討。實驗首先以氫焰對Pt(100)電極進行退火，並在氫氣吹拂下冷卻後進行實驗，透過浸泡法與添加法將鉛修飾於Pt(100)電極，在-200 mV(vs. Ag/AgCl)電位進行STM成像，鉛覆蓋結果呈現√2×2√2結構，而當電位正移至-100 mV時則為√2×√2結構，並透過循環伏安法針對鉛氧化剝除電荷量得到鉛於電極表面覆蓋度為0.5。此外，把循環伏安法掃瞄範圍擴大至鉛的過電位時，多層鉛的沉積會先由二維方向向外擴張，再慢慢沿三維方向成長至大片平坦島狀，同時白金表面與底層鉛受到電位的影響進行混合形成合金，使電位正移至0 V時單層鉛√2×√2結構與白金表層1×1結構轉變為無序且粗糙的表面。經過鉛預修飾後的Pt(100)電極能有效抑制甲酸氧化反應中間體一氧化碳的吸附，使原本純Pt(100)進行甲酸氧化後一旦被一氧化碳吸附，必須於電位 0.5 V以後才具甲酸氧化活性，提前至-0.1 V即開始有甲酸氧化現象產生，電流也由0.41 mA/cm2提升至7.1 mA/cm2，可明顯看出經鉛修飾後之Pt(100)在甲酸氧化活性較純Pt(100)大。接著把甲酸更換成甲醛與甲醇進行循環伏安法實驗以得知兩種分子氧化活性變化，結果顯示經鉛修飾Pt(100)電極同樣對甲醛具催化效果，氧化電位相較於裸Pt(100)提前了0.1 V，最大氧化電流也由1.1 mA/cm2提升至4.1 mA/cm2，明顯較純Pt(100)好。然而對於甲醇氧化不具明顯催化效果，推測主因為反應過程需透過白金與氫的強吸附力，在施加電位的過程中對碳氧雙鍵鄰位上的氫進行作用，使碳氫鍵斷裂而形成二氧化碳，然而甲醇分子中碳氧雙鍵鄰位上為碳而非氫，故整體催化效果不彰。;In this study, cyclic voltammetry (CV) and scanning tunneling microsope (STM) were used to investigate the structure of lead modification on the surface of the Pt (100) electrode and its catalytic effect on formic acid oxidation. In the experiment, the Pt(100) electrode was annealed with a hydrogen flame and cooled under hydrogenblowing, and the lead was modified on the Pt(100) electrode by immersion method or addition method, and the structure of √2×√2 was shown under STM imaging at -0.2 V(vs. Ag/ AgCl). When the potential was shifted to -0.1 V, the lead overlayer structure results was transformed into√2×√2. The coverage of lead on the electrode surface was 0.5 by cyclic voltammetry for lead oxidation and exfoliation. In addition, when the scanning range of cyclic voltammetry is extended to the overpotential of lead, the deposition of multilayer lead will first expand outward from the two dimensional direction, and then slowly grow into a large flat island in the dimensional direction, and at the same time, the platinum surface and the underlying lead will be mixed to form an alloy under the influence of the potential, so that when the potential is moved to 0 V, the single layer lead√2×√2structure and the platinum surface 1×1 structure will be transformed into disordered and rough surface The Pt(100) electrode after lead premodification can effectively inhibit the adsorption of carbon monoxide, an intermediate in the formic acid oxidation reaction, so that once the bare Pt(100) is adsorbed by carbon monoxide after formic acid oxidation, it must have formic acid oxidation activity after the potential is 0.5 V, and the formic acid oxidation phenomenon begin to occur when it reaches -0.1 V in advance, and the current is also increased from 0.41 mA/cm2 to 7.1 mA/cm2. The results showed that the Pb-modified Pt(100) electrode also had a catalytic effect on formaldehyde, the oxidation potential was 0.1 V earlier than that of bare Pt(100) and the maximum iii oxidation current was increased from the 1.1 mA/cm2 to 4.1 mA/cm2，but it did not have an obvious catalytic effect on methanol oxidation, which breaks the carbon-hydrogen bond to form a carbon dioxide intermediate, but the carbon-oxygen double bond in the methanol molecule is adjacent to carbon instead of hydrogen, so the overall catalytic effect is not well.
Appears in Collections:	[Graduate Institute of Chemistry] Electronic Thesis & Dissertation

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