【摘要】：燃料電池是一種能將燃料中的化學(xué)能直接轉(zhuǎn)變成電能的新型電源裝置。以硼氫化鈉(NaBH4)堿性水溶液為燃料的直接硼氫化物燃料電池(DBFC)使用的燃料性質(zhì)穩(wěn)定,易于儲存和運輸,電池理論電壓與比能量高。理論上,BH4-的電氧化過程為8 e-轉(zhuǎn)移反應(yīng),但由于BH4-中的H-組分具有1S2的特殊結(jié)構(gòu),易失去電子,性質(zhì)極不穩(wěn)定。所以,BH4-在進(jìn)行直接電氧化反應(yīng)的同時還會發(fā)生水解反應(yīng),這無疑會降低燃料利用率。因此,研究BH4-在不同金屬電極材料上的電化學(xué)氧化反應(yīng)行為及放電特性,開發(fā)高效多功能復(fù)合電極催化劑,具有十分重要的意義。首先,本文以連續(xù)兩步化學(xué)還原法制備了不同比例的碳載核殼結(jié)構(gòu)Cu-Pd (Cu@Pd/C)納米粒子催化劑。并利用XRD、TEM、EDS等對納米粒子進(jìn)行物理表征；采用CV、CP、CA和電池測試等技術(shù)進(jìn)行電化學(xué)分析。結(jié)果表明：所制備的Cu@Pd/C粒徑為9m左右的近似球形的核殼結(jié)構(gòu)納米粒子,但存在一定程度的團(tuán)聚現(xiàn)象。Cu@Pd/C均有比單金屬Pd/C更大的電化學(xué)活性面積(ECSA),并且展示出較好的電催化性能。不同Cu、Pd比例的納米粒子表現(xiàn)出不同的催化性能,當(dāng)Cu1@Pd1/C用作DBHFC陽極催化劑時,在20℃時獲得的功率密度達(dá)到40mWcm-2。其次,本文以反相微乳液——連續(xù)兩步化學(xué)還原法制備了不同比例的Ni@Au/C催化劑。通過物理和電化學(xué)方法表征得出以下結(jié)果：Ni@Au/C納米粒子粒徑約為10nm的核殼結(jié)構(gòu),具有較好的分散性。隨著Au殼層厚度的逐漸減薄,催化性能表現(xiàn)為先增大后減小的趨勢。計算出Au/C、 Ni1@Au2/C、Ni1@Au1/C和Ni2@Au1/C的ECSA分別為161.0 cm2 mg-1,348.1 cm2mg-1,815.7cm2mg-1和402.4 cm2 mg-1, Ni1@Au1/C有最大的ECSA并且也有較好的穩(wěn)定性,在CV實驗中基于al氧化峰轉(zhuǎn)移的電子數(shù)為6.6。在20℃時,以Ni1@Au1/C為陽極催化劑,Pt網(wǎng)(1 cm×1 cm)為陰極電極組裝成DBHFC,獲得的功率密度為74mWcm-2,是相同條件下Au/C催化劑的4倍。本論文所制備的核殼結(jié)構(gòu)催化劑對BH；均表現(xiàn)出比單金屬催化劑更好的電催化氧化性能,這是由核殼結(jié)構(gòu)特殊的電子效應(yīng)和幾何效應(yīng)引起的。在一定厚度的殼層時,核心金屬對殼層金屬的d電子軌道產(chǎn)生適宜的誘導(dǎo)效應(yīng),使得BH4-在殼層金屬表面的吸附力適中,比較有利于BH4-的吸附和反應(yīng)產(chǎn)物的脫附。本文制備的Cu1@Pd1/C或Ni1@Au1/C納米粒子的催化性能較好,這與其微觀結(jié)構(gòu)有關(guān),兩種催化劑殼層均排列了3～4層Pd原子或Au原子,同時,Cu1@Pd1/C和Ni1@Au1/C均具有的較大的ECSA。
[Abstract]:Fuel cell is a new type of power supply device which can directly convert the chemical energy in fuel into electric energy. The direct borohydrate fuel cell (DBFC) with sodium borohydrate (NaBH4) alkaline aqueous solution as fuel has stable fuel properties, easy storage and transportation, and high theoretical voltage and specific energy of the cell. In theory, the electrooxidation process of BH4- is 8 e-transfer reaction, but because the H-component in BH4- has the special structure of 1S2, it is easy to lose electrons and the properties are very unstable. Therefore, the hydrolysis of BH4- will occur at the same time of direct electrooxidation, which will undoubtedly reduce the fuel utilization rate. Therefore, it is of great significance to study the electrochemical oxidation behavior and discharge characteristics of BH4- on different metal electrode materials and to develop efficient multifunctional composite electrode catalysts. Firstly, different proportion of carbon-supported core-shell Cu-Pd (Cu@Pd/C) nanoparticles catalysts were prepared by continuous two-step chemical reduction method. The nanoparticles were physically characterized by XRD,TEM,EDS and electrochemical analysis was carried out by CV,CP,CA and battery testing. The results show that the prepared Cu@Pd/C nanoparticles with approximately spherical core-shell structure with a particle size of about 9m have a certain degree of agglomeration. Copper @ Pd/C has a larger electrochemical active area (ECSA), than monometallic Pd/C and shows better electrocatalytic performance. The catalytic performance of nanoparticles with different Cu,Pd ratios is different. When Cu1@Pd1/C is used as anode catalyst for DBHFC, the power density can reach 40 MW / cm at 20 鈩，

本文編號：2506239