氮氣直流脈衝常壓噴射電漿製備鉑鐵催化劑之電化學及穿透式電子顯微鏡分析

Abstract

本研究探討氮氣直流脈衝噴射電漿製備鉑鐵催化劑的兩個實驗變因:處理時間及氯鉑酸/硝酸鐵混和溶液濃度。實驗第一部分以氯鉑酸/硝酸鐵1:1溶液混合溶液旋轉塗佈至氟摻雜氧化錫(FTO)導電玻璃基板上，經由常壓電漿處理後，電漿高反應性粒子以及熱效應和液態前趨薄膜反應生成金屬/金屬氧化物薄膜及奈米粒子。由掃式電子顯微鏡(SEM)可觀察到鉑鐵奈米粒子均勻分布基板表面上。而由掃描式穿透式電子顯微鏡(STEM)截面影像上可以觀察在奈米粒子下有一層約20 nm至70 nm的連續薄膜，由能量散射頻譜成相(EDS-mapping)可以觀察出鉑和鐵的成分均勻分布。而由高解析度穿透電子顯微鏡影像(HR-TEM)影像可以看出所形成的金屬奈米粒子為非晶和奈米晶的混合相。再經由X-光電子能譜(XPS)分析發現鉑以金屬相存在，而鐵則多以氧化態存在。透過電化學分析不同常壓噴射電漿製備鉑鐵催化劑，可發現在5秒的常壓電漿處理就可以大伏提高電催化效應，用於染料敏化太陽能電池對電極也具有接近最佳的電池效率。第二部分固定常壓電漿處理時間，進行氯鉑酸/硝酸鐵1:1、1:5、1:10溶液比例之比較，可以得知鉑鐵催化劑經常壓電漿處理5秒後，透過電化學分析就都具有催化能力。在較高鉑含量之催化劑具有較佳之催化性質。實驗結果證實氮氣常壓噴射電漿具有快速製備鉑鐵催化劑之能力。

This study investigates two factors for nitrogen DC-pulse atmospheric pressure plasma jet (APPJ) synthesized PtFe catalysts: 1. APPJ processing time, 2. chloroplatinic acid/iron nitrate concentration ratio. In the first part of this study, 1:1 chloroplatinic acid/iron nitrate volume ratio solution is spin-coated onto fluorine-doped tin oxide (FTO) glass substrate. After APPJ processing, PtFe nanocompounds are produced bytje synergetic effect of high reactive plasma species and heat. Scanning electron microscopy (SEM) indicates PtFe nanoparticles well distribute on FTO substrates. Scanning transmission electron microscopy (STEM) cross-sectional image shows an underlying continuous thin film with 20-70 nm thickness beneath the nanoparticles. Energy-dispersive spectroscopy mapping (EDS-mapping) shows the contents of Pt and Fe are pretty uniformly distributed. High resolution transmission electron microscopy (HR-TEM) reveals that the nanocompounds consist of amorphous and nanocrystalline phases. X-ray photoelectron spectroscopy (XPS) suggests that most of Pt is in metallic phase whereas Fe is present in oxidized form. Electrochemical analysis shows that 5 s APPJ processing can singnificantly improve the electrocatalytic effect of the PtFe. When used for the counter electrode of dye-sensitized solar cells (DSSCs), the cell efficiency already approaches the optimal efficiency with 5-s APPJ-processed PtFe as the counter electrode. In the second part of this experiment, the APPJ processing is fixed whereas the chloroplatinic acid/iron nitrate volume ratio is varied as 1:1, 1:5, and 1:10. For all three cases, 5-s APPJ processing can significantly improve the cell efficiency. The catalyst with higher Pt content shows better electrocatalytic performance. Our experimental results demonstrate that nitrogen APPJ is capable of rapidly synthesizing PtFe catalysts.