負載於碳黑上鈀-鈷奈米合金氧氣還原反應電催化劑之製備與性質分析

本研究為負載於碳黑上鈀-鈷奈米合金氧氣還原反應電催化劑之製備與性質分析，實驗架構主要分為兩部份。 Part 1：使用硼氫化鈉做為還原劑的含浸法製作PdCo奈米合金並負載在碳上，然後在350 oC退火。可以得到四組不同原子比例的催化劑，Pd/C、Pd88Co12/C、Pd76Co24/C、Pd50Co50/C。對製程之電催化劑使用X光繞射分析儀、穿透式電子顯微鏡、化學影像能譜分析儀和動態光散射分析儀測量其表面形態與結構性質分析；並使用旋轉圓盤電極(RDE)進行循環伏安法、線性掃描伏安法，分析電化學活性表面積與ORR效能。PdCo奈米顆粒粒徑為3.9 nm (Pd88Co12/C)到5.5 nm (Pd50Co50/C)之間，PdXCoY/C電催化劑的金屬含量約20 wt%，從電化學測試發現催化活性為Pd88Co12/C > Pd76Co24/C >Pd50Co50/C > Pd/C。 Part 2：別於以往對於PdXCoY/C電催化劑使用熱處理的方式改良其活性，開發新種電化學法氧化處理PdXCoY/C電催化劑並對ORR催化活性進行分析。在鹼性環境下使用定電位氧化PdXCoY/C電催化劑，結果發現電化學法氧化處理PdXCoY/C會造成電催化活性下降，ORR活性也會下降，無法如文獻中熱處理氧化一樣提升ORR活性。

關鍵字

氧氣還原反應；鈀鈷奈米合金；電催化劑

並列摘要

Pd-Co nanoalloy electrocatalysts supported on Vulcan XC-72 carbon black (PdCo/C) for oxygen reduction reaction (ORR) are synthesized and characterization in this study. This study has two part experiments. Part 1：PdCo nanoalloys are prepared by impregnation method using sodium borohydride as the reducing agent and then annealed at 350 oC. Electrocatalysts with various Pd:Co atomic ratios of 88:12 (Pd88Co12/C) , 76:24 (Pd76Co24/C) and 50:50 (Pd50Co50/C) are obtained.Pd/C electrocatalyst is also prepared using the same method for comparison.Transmission electron microscope, scanning electron microscopy with energy dispersive spectroscopy and X-ray diffractometer are used to analysis the structure and composition of the electrocatalysts.Electrochemical behaviors and electrocatalytic activity toward ORR of these electrocatalysts are investigated and compared by cyclic voltammetry (CV) and rotating disk electrode (RDE) experiments. The size of the PdCo nanoalloys is ranging from 3.9 nm (Pd88Co12/C) to 5.5 nm (Pd50Co50/C), and the total metal loading of these electrocatalysts is around 20 wt%. Electrochemical active surface area (ECSA) of the electrocatalysts is estimated from CV, and Pd88Co12/C shows a higher ECSA than that of Pd/C. According to the RDE experiments, Pd88Co12/C shows the highest ORR mass activity among all the electrocatalysts prepared in this study, and which is 1.9-fold higher than that of Pd/C. The electron transfer number of ORR on these electrocatalysts is about 4 as estimated by Koutecky-Levich equation. Part 2：Develop the new oxidation procedure of PdXCoY / C for different oxidation potentials on ECSA and ORR activity. The PdXCoY / C electrocatalysts are oxidized in alkaline condition by using chronoamperometry. In summuy, electrochemical oxidation of PdXCoY / C are decreased electrocatalytic activity and decreased ORR activity. The ORR activity can not be enhanced as the case of heat treatment oxidation in the literature.

並列關鍵字

oxygen reduction reaction ； palladium-cobalt nanoalloy ； electrocatalyst

參考文獻

[1] S. Mekhilef, R. Saidur, and A. Safari, "Comparative study of different fuel cell technologies," Renewable and Sustainable Energy Reviews 16 ,2012, 981-989.

[2] C. Song and J. Zhang, "Electrocatalytic oxygen reduction reaction," Springer, 2008, 89-134.

[3] K. Oishi and O. Savadogo, "Correlation between the physico-chemical properties and the oxygen reduction reaction electro catalytic activity in acid medium of Pd–Co alloys synthesized by ultrasonic spray method," Electrochimica Acta 98, 2013, 225-238.

[4] H. Liu and A. Manthiram, "Controlled synthesis and characterization of carbon-supported Pd 4 Co nanoalloy electrocatalysts for oxygen reduction reaction in fuel cells," Energy & Environmental Science 2, 2009, 124-132.

[5] X. Li, Q. Huang, Z. Zou, B. Xia, and H. Yang, "Low temperature preparation of carbon-supported Pd Co alloy electrocatalysts for methanol-tolerant oxygen reduction reaction," Electrochimica Acta 53, 2008, 6662-6667.

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負載於碳黑上鈀-鈷奈米合金氧氣還原反應電催化劑之製備與性質分析

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