【摘要】：直接甲醇燃料電池(DMFC)以其高能源效率和環(huán)境友好的優(yōu)點,在迫切需求清潔能源的今天,成為了一個很有吸引力的選擇。為了提高DMFC的性能,高活性的電催化劑顯得十分重要。隨著自然資源的逐漸枯竭,尤其是罕見的金屬如鉑、鈀等,研究開發(fā)高效、廉價的催化劑已經(jīng)成為了這一領域的焦點。 非晶態(tài)材料具有短程無序,長程有序的特殊結構,其高濃度的配位不飽和位點導致其優(yōu)良的催化活性與選擇性,可以很容易的進行反應。納米材料具有大的比表面積,高表面活性中心密度與表面能,將非晶態(tài)與納米結合在一起,可以導致更高的電化學容量和更強的電化學活性,可以作為提高催化劑電催化活性的有效手段。 在這篇論文中,通過化學還原法合成了不同Ni/B原子比的非晶態(tài)Ni-B合金納米顆粒,采用HRTEM、SAED、XRD、DSC、XPS等手段對其進行表征。采用循環(huán)伏安法對非晶態(tài)合金納米粒子的電化學性能進行測試。 物理表征結果表明：經(jīng)過XRD檢測,Ni-B合金未發(fā)現(xiàn)晶態(tài)金屬的特征峰,通過SAED和HRTEM可以確定合金具有非晶態(tài)的長程無序、短程有序的結構特點,觀察到制備的非晶態(tài)Ni-B合金納米粒子為球形或者類球形,平均粒徑為4-7納米,團聚現(xiàn)象不明顯。DSC的測試結果表明,非晶態(tài)Ni-B合金納米顆粒最早在342.8℃處出現(xiàn)放熱峰,隨著Ni-B合金中B原子比例的增加,合金的放熱峰的峰溫先增大后減小,其中Ni1B4開始晶化的溫度最高,說明其非晶態(tài)結構較其他催化劑有更好的熱穩(wěn)定性,較難晶化為金屬Ni與B元素。XPS分析的結果表明,非晶態(tài)Ni-B合金中,B失去部分電子,而Ni則富余電子,Ni-B之間具有電子效應。顆粒表面Ni原子濃度隨合金中B比例的增大先減小后增大,其中,Ni1B3的濃度最小。而氧化態(tài)鎳的原子濃度也隨合金中B比例的增加變化不明顯。隨反應物中Ni濃度的增加,氧化態(tài)Ni的濃度逐漸減小,而Ni原子的濃度則逐漸增大。 應用循環(huán)伏安法首次研究了堿性介質中非晶態(tài)Ni-B合金納米顆粒對甲醇的電催化反應。結果表明,非晶態(tài)Ni-B合金納米顆粒對甲醇有著較高的電催化氧化活性。對Ni-B非晶態(tài)合金納米合金的對不同甲醇濃度的NaOH溶液中循環(huán)伏安曲線的分析,發(fā)現(xiàn)隨甲醇濃度愈大,氧化峰電流密度也隨之越大。隨著非晶態(tài)合金中B含量的增加,其電催化氧化甲醇的能力先減弱后增強,其中,Ni1B4的氧化能力最弱。隨反應物中Ni濃度的增加,非晶態(tài)Ni1B2納米合金的電催化甲醇的性能逐漸增加。通過對催化劑進行50次掃描,非晶態(tài)合金的峰電流密度下降比例為26.8%。對比非晶態(tài)Ni1B4與晶態(tài)Ni1B4對甲醇的電催化氧化發(fā)現(xiàn),非晶態(tài)合金具有較低的起始電位與峰電位,但是其氧化峰電流密度卻低于晶態(tài)合金。
[Abstract]:Direct methanol fuel cell (DMFC) has become an attractive choice because of its advantages of high energy efficiency and environmental friendliness. In order to improve the performance of DMFC, high activity electrocatalyst is very important. With the gradual depletion of natural resources, especially rare metals such as platinum, palladium, research and development of efficient, cheap catalysts have become the focus of this field. The amorphous material has a special structure of short range disorder and long order. Its high concentration of coordination unsaturated site leads to its excellent catalytic activity and selectivity, so it can be easily reacted. Nanomaterials have large specific surface area, high surface active center density and surface energy, combine amorphous state with nanometer, can lead to higher electrochemical capacity and stronger electrochemical activity. It can be used as an effective means to improve the electrocatalytic activity of the catalyst. In this paper, amorphous Ni-B alloy nanoparticles with different Ni/B atomic ratios were synthesized by chemical reduction method. The electrochemical properties of amorphous alloy nanoparticles were measured by cyclic voltammetry. The results of physical characterization show that there is no characteristic peak of crystalline metal in Ni-B alloy by XRD. The structural characteristics of amorphous long range disorder and short range order can be determined by SAED and HRTEM. It was observed that the amorphous Ni-B alloy nanoparticles were spherical or spherical, with an average particle size of 4-7 nanometers. The agglomeration phenomenon was not obvious. The results showed that the exothermic peak of amorphous Ni-B alloy nanoparticles appeared at 342.8 鈩，

本文編號：2168993