以官能基化奈米碳管作為奈米鉑觸媒之載體的特性研究

Characterization of Platinum Nanocatalysts Deposited on Functionalized Carbon Nanotubes

江右君(Yu-Chun Chiang) ； 吳帛軒(Pai-Hsuan Wu) ； 岳恆屹(Heng-I Yueh) ； 林俊宇(Chun-Yu Lin) ； 楊景松(Ching-Sung Yang)

《燃燒季刊》 114期 (2021/08) Pp. 9-23

https://doi.org/10.30041/CQ.202108_(114).0002

摘要

本研究將奈米碳管（Carbon nanotubes, CNTs）予以檸檬酸氧化或高分子（Polybenzimidazole, PBI）包覆，再利用反微胞法於其表面沈積奈米Pt粒子。利用CNTs的表面官能基化，改善與奈米Pt粒子的界面鍵結，強化交互作用力。檸檬酸氧化為常見表面稼接含氧官能基的方法；PBI及其衍生物已發現為高溫質子交換膜燃料電池操作上最具潛力的高分子材料之一，因其質子傳導能力除了利用運載機理外，亦可透過跳躍機理。研究發現，Pt/cCNT和Pt/PBI-CNTs之Pt平均粒徑分別為2.55 ± 0.58和3.51 ± 0.80 nm。沈積在PBI-CNT表面之Pt的結晶化程度較佳，但Pt/cCNT之抗氧化能力優於Pt/PBI-CNTs。奈米Pt之表面化態分佈明顯受到基材表面改質的影響；Pt/cCNT之Pt粒子以金屬Pt最多（52.2 at. %），但Pt/PBI-CNT則以Pt（II）為主（73.5 at. %）、且有極低的Pt（IV）殘留。Pt/cCNT和Pt/PBI-CNT之電化學活性面積（ECSA）分別約為51和56 m^2/g，優於商用Pt/C樣本；Pt的利用率可達46 %（Pt/cCNT）和70 %（Pt/PBI-CNT）。循環操作600圈後，ECSA的衰減率分別約為8 %（Pt/cCNT）、9 %（Pt/PBI-CNT）、和75 %（Pt/C）。研究結果顯示，檸檬酸氧化或PBI包覆CNTs均可使Pt有效發揮其電化學活性和耐久性，可能因Pt離子和表面含氧官能基或PBI分子形成配位所致。而Pt/PBI-CNT的電化學活性稍佳，可能係來自Triple-phase boundary奈米結構的形成。

關鍵字

奈米碳管 ； 官能基化 ； 觸媒 ； 材料特性分析 ； 電化學活性

並列摘要

In this study, carbon nanotubes (CNTs) were functionalized using citric acid (denoted as cCNT) or polybenzimidazole (denoted as PBI-CNT) and Pt nanoparticles were then deposited on the functionalized CNTs by means of a colloidal process. To improve the interfacial interactions between Pt nanoparticles and the CNTs through the functionalization of CNTs. Citric acid oxidation is a commonly used method for introducing the surface oxides. PBI and its derivatives are some of the most promising candidates for high temperatureproton exchange membrane fuel cells since the proton transfer occurs not only by the vehicle mechanism but also by the hopping mechanism. The results showed that the average sizes of Pt nanoparticles were 2.55 ± 0.58 nm (Pt/cCNT) and 3.51 ± 0.80 nm (Pt/PBI-CNT). The Pt nanoparticles deposited on PBI-CNT exhibited excellent crystallization, while the resistance to oxidation of Pt/cCNT was better than Pt/PBI-CNT. The chemical states of Pt were dependent on the functionalization of CNTs. Metal Pt was predominant in Pt/cCNT, but the Pt (II) was the most abundant chemical state in Pt/PBI-CNT with a low content of Pt (IV). The values of the electrochemical surface area (ECSA) were 51 (Pt/cCNT) and 56 (Pt/PBI-CNT) m^2/g, much better than that of one commercial Pt/C sample. Moreover, the Pt utilization efficiency were 46 % for Pt/cCNT and 70 % for Pt/PBI-CNT, respectively. The degradation of ECSA values after 600 cycles was 8% for Pt/cCNT or 9 % for Pt/PBI-CNT, much excellent than that of the commercial Pt/C (75%). It was believed that the long fibrous structure of CNTs and strong interactions between Pt particles and CNTs were of great significance for exerting the electroactivity of Pt particles. Moreover, the coordination of the Pt ions with the surface oxides or PBI molecules could be responsible for the high electroactivity and utilization. The high ECSA of Pt/PBI-CNT could also be attributed to the formation of triple-phase boundary.

並列關鍵字

Carbon nanotubes ； Functionalization ； Catalyst ； Characterization ； Electrochemical activity