鈀銀鈷和銀鈷金屬合金納米催化劑的合成及其電化學性能研究
發(fā)布時間：2018-10-14 19:13
【摘要】：由于化石燃料的過度消耗及自然資源匱乏等原因使得新能源及可持續(xù)能源的開發(fā)利用迫在眉睫。Li電池雖然現(xiàn)在占據(jù)市場較大的份額,但是仍有很多技術(shù)問題。燃料電池是一種只需定期充入燃料就可以將燃料的化學能直接轉(zhuǎn)化為電能的裝置,并能夠不斷地提供能量,且無污染,轉(zhuǎn)化率高,是一種理想的能量轉(zhuǎn)換方式。催化劑是燃料電池中最關(guān)鍵的一部分,主流催化劑中貴金屬Pt和Pd的含量往往較高,這就導(dǎo)致電池的成本增加,這一問題極大的限制了燃料電池的發(fā)展及應(yīng)用。因此,本著催化劑具有低成本高催化性能的研究目標,本文通過有機合成制備出具有成本低電催化性能好的金屬合金納米催化劑AgCo和Co摻雜的PdAgCo。我們首先通過電化學工作站進行循環(huán)伏安掃描(CV),然后對PdAgCo和AgCo分別進行直接甲酸氧化測試(FAO),氧還原測試(ORR)以及穩(wěn)定性測試,并通過透射電鏡(TEM),高倍電鏡(HRTEM),X射線衍射(XRD)對催化劑的形貌、結(jié)構(gòu)、物相及組成進行了表征和分析。(1)本文通過固定加入反應(yīng)體系的表面還原劑(油胺OA)的量,分別合成了單分散的Pd AgCo和Pd Ag納米顆粒,透射電鏡下可以看到,PdAg合金納米催化劑是直徑為6 nm左右的顆粒,大小比較均一,Co摻雜的PdAgCo是粒徑為8 nm左右的納米球體,粒徑也相對比較均一。XRD數(shù)據(jù)顯示,在PdAg納米顆粒主要以111面的PdAg合金的形式存在的,在PdAgCo/C納米顆粒中盡管只有少量的Co元素摻雜進去,也形成了三金屬的合金納米顆粒。電化學測試結(jié)果表明PdAgCo/C(1 133.249 mAmgPd-1)的甲酸氧化催化性能是商業(yè)Pd/C(483.563 mAmgPd-1])的2.4倍以及雙金屬PdAg/C(680.741 mAmgPd-1)的1.7倍,即少量Co元素的摻雜對雙金屬PdAg的甲酸氧化性能也有較大的提高。此實驗中的油胺是一種長鏈有機還原劑,除了能夠控制顆粒形貌外,還起到封端劑的作用。(2)通過簡單的操作步驟,在有機液相中還原制備了一系列不同煅燒溫度的AgCo和不同負載載體的AgCo,來比較其電催化性能。透射電鏡(TEM)顯示部分AgCo納米顆粒為8nm左右的類球形顆粒,而部分AgCo納米顆粒則發(fā)生了融合。XRD數(shù)據(jù)確認了所制備材料部分為fcc結(jié)構(gòu)的AgCo合金。電化學測試表明:金屬Ag和Co發(fā)生融合的最佳煅燒溫度是550℃,在此溫度條件下將活性炭載體更換為ZIF-8,可得到AgCo/ZIF-8-550℃納米顆粒,該顆粒的電化學活性優(yōu)于AgCo/C-550℃納米顆粒的。(3)結(jié)合理論計算的指導(dǎo),我們還通過控制不同的煅燒啊燒升溫速度,來獲得最佳催化性能的AgCo催化劑,即分別以5℃/min、8℃/min和10℃/min煅燒AgCo/ZIF-8納米催化劑至550℃。電化學測試表明,合成的AgCo/ZIF-8-550℃在煅燒速度為8℃/min州其具有比較好的氧還原(ORR)活性和穩(wěn)定性。
[Abstract]:Because of the excessive consumption of fossil fuels and the shortage of natural resources, it is urgent to develop and utilize new and sustainable energy. Although Li batteries now occupy a large market share, there are still many technical problems. Fuel cell is a kind of device which can directly convert the chemical energy of fuel into electric energy by filling fuel periodically, and it can provide energy continuously, without pollution and high conversion rate, so it is an ideal energy conversion mode. Catalyst is the most important part of fuel cell. The content of noble metal Pt and Pd in the mainstream catalyst is often higher, which leads to the increase of the cost of fuel cell. This problem greatly limits the development and application of fuel cell. Therefore, in line with the research goal of low cost and high catalytic performance of catalysts, metal alloy nano-catalysts AgCo and PdAgCo. doped with Co were prepared by organic synthesis. We first performed cyclic voltammetry scanning (CV), on an electrochemical workstation and then performed direct formic acid oxidation test (FAO), oxygen reduction test (ORR) and stability test on PdAgCo and AgCo respectively. The morphology, structure, phase and composition of the catalyst were characterized and analyzed by transmission electron microscope (TEM),) high power electron microscope (HRTEM), X ray diffraction (XRD). (1) the amount of surface reductant (oleamine OA) was fixed in the reaction system. Monodisperse Pd AgCo and Pd Ag nanocrystals were synthesized respectively. The results of transmission electron microscopy showed that the PdAg alloy nanocrystalline catalyst was about 6 nm in diameter and uniform in size, and Co doped PdAgCo was a nano-sphere with a diameter of about 8 nm. XRD data show that PdAg nanoparticles mainly exist in the form of 111-plane PdAg alloy, and in PdAgCo/C nanoparticles, even though only a small amount of Co elements are doped in them, tri-metal alloy nanoparticles are formed. The results of electrochemical measurement show that the catalytic performance of PdAgCo/C (1 133.249 mAmgPd-1) for formic acid oxidation is 2. 4 times of that for commercial Pd/C (483.563 mAmgPd-1) and 1. 7 times for bimetallic PdAg/C (680.741 mAmgPd-1). The oleamine in this experiment is a kind of long chain organic reductant, which can not only control the morphology of particles, but also act as an entrapment agent. (2) through simple operation steps, A series of AgCo calcined at different temperatures and AgCo, supported on different supports were prepared by reduction in organic liquid phase to compare their electrocatalytic properties. Transmission electron microscopy (TEM) showed that some AgCo nanoparticles were spherical particles about 8nm, while some AgCo nanoparticles were fused. XRD data confirmed that some of the prepared AgCo nanoparticles were AgCo alloys with fcc structure. The electrochemical test showed that the optimal calcination temperature for fusion of metal Ag and Co was 550 鈩，
本文編號：2271381
[Abstract]:Because of the excessive consumption of fossil fuels and the shortage of natural resources, it is urgent to develop and utilize new and sustainable energy. Although Li batteries now occupy a large market share, there are still many technical problems. Fuel cell is a kind of device which can directly convert the chemical energy of fuel into electric energy by filling fuel periodically, and it can provide energy continuously, without pollution and high conversion rate, so it is an ideal energy conversion mode. Catalyst is the most important part of fuel cell. The content of noble metal Pt and Pd in the mainstream catalyst is often higher, which leads to the increase of the cost of fuel cell. This problem greatly limits the development and application of fuel cell. Therefore, in line with the research goal of low cost and high catalytic performance of catalysts, metal alloy nano-catalysts AgCo and PdAgCo. doped with Co were prepared by organic synthesis. We first performed cyclic voltammetry scanning (CV), on an electrochemical workstation and then performed direct formic acid oxidation test (FAO), oxygen reduction test (ORR) and stability test on PdAgCo and AgCo respectively. The morphology, structure, phase and composition of the catalyst were characterized and analyzed by transmission electron microscope (TEM),) high power electron microscope (HRTEM), X ray diffraction (XRD). (1) the amount of surface reductant (oleamine OA) was fixed in the reaction system. Monodisperse Pd AgCo and Pd Ag nanocrystals were synthesized respectively. The results of transmission electron microscopy showed that the PdAg alloy nanocrystalline catalyst was about 6 nm in diameter and uniform in size, and Co doped PdAgCo was a nano-sphere with a diameter of about 8 nm. XRD data show that PdAg nanoparticles mainly exist in the form of 111-plane PdAg alloy, and in PdAgCo/C nanoparticles, even though only a small amount of Co elements are doped in them, tri-metal alloy nanoparticles are formed. The results of electrochemical measurement show that the catalytic performance of PdAgCo/C (1 133.249 mAmgPd-1) for formic acid oxidation is 2. 4 times of that for commercial Pd/C (483.563 mAmgPd-1) and 1. 7 times for bimetallic PdAg/C (680.741 mAmgPd-1). The oleamine in this experiment is a kind of long chain organic reductant, which can not only control the morphology of particles, but also act as an entrapment agent. (2) through simple operation steps, A series of AgCo calcined at different temperatures and AgCo, supported on different supports were prepared by reduction in organic liquid phase to compare their electrocatalytic properties. Transmission electron microscopy (TEM) showed that some AgCo nanoparticles were spherical particles about 8nm, while some AgCo nanoparticles were fused. XRD data confirmed that some of the prepared AgCo nanoparticles were AgCo alloys with fcc structure. The electrochemical test showed that the optimal calcination temperature for fusion of metal Ag and Co was 550 鈩，
本文編號：2271381
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