發(fā)布時(shí)間：2019-01-29 20:18

【摘要】：為了研究銅基合金納米管的成分及其合金化效應(yīng)對(duì)其電催化性能的影響,本論文以銅納米線為模板,采用電化學(xué)置換的合成方法,分別制備了不同種類(lèi)的銅基多元合金納米管并對(duì)其性能及氧氣還原反應(yīng)的機(jī)理進(jìn)行了研究。首先以氯鉑酸為鉑源,銅納米線為前驅(qū)體模板,通過(guò)控制氯鉑酸的滴加量,制備了不同成分的銅鉑二元合金納米管。制得的納米管的直徑在100-150納米之間,壁厚15-25納米,管長(zhǎng)2-3微米;銅鉑元素在合金納米管壁上均勻分布。對(duì)不同成分的銅鉑合金納米管進(jìn)行了電催化性能的研究。其中,成分為Cu40Pt60催化性能最優(yōu),其催化氧氣還原反應(yīng)的起始電位和半波電位分別超出商業(yè)Pt/C 57mV和20m V,在催化甲醇氧化過(guò)程中正負(fù)掃峰電流密度的比值約為商業(yè)Pt/C的1.57倍。材料合金化效應(yīng)能夠大幅提高其電催化活性。材料氧化還原反應(yīng)機(jī)理研究結(jié)果表明:相較于商業(yè)Pt/C,銅鉑合金中由于銅鉑間的合金化效應(yīng)改變了 Pt 5d軌道的電子結(jié)構(gòu),從而減弱了氫氧根與合金表面相互作用,提高了電催化反應(yīng)的速率。其次,為了降低上述二元合金的成本,使用相對(duì)便宜的氯化鈀替換了氯鉑酸,采用相同的電化學(xué)置換方法,制備了銅鈀合金納米管。結(jié)果發(fā)現(xiàn),該催化表現(xiàn)出優(yōu)秀的催化甲醇氧化性能,大部分催化劑催化甲醇氧化的性能優(yōu)于商業(yè)Pt/C。其中成分為Cu20Pd80性能最優(yōu),為了進(jìn)一步探明合金化效應(yīng)對(duì)催化性能的影響,在上述二元合金的基礎(chǔ)上,又制備了銅鉑鈀三元合金納米管。在三元合金納米管中各金屬元素均勻分布在合金納米管壁上,其合金化程度達(dá)到原子級(jí)水平。由于金屬間的協(xié)同效應(yīng)使得三元合金具有優(yōu)異的催化性能。不同成分的三元合金的催化氧氣還原性能均優(yōu)于商業(yè)Pt/C,其中性能最優(yōu)的為Cu28.5Pt37.2Pd34.3,在酸性體系下其起始電位和半波電位分別超出商業(yè)Pt/C 88mV和49mV;在電位值為0.85V(vs.RHE)處其催化氧氣還原動(dòng)力學(xué)電流密度約為商業(yè)Pt/C的8倍。此外,其催化甲醇氧化的正負(fù)掃峰電流密度的比值約為商業(yè)Pt/C的1.9倍。最后,通過(guò)比較三種不同類(lèi)型的合金催化劑性能,催化活性由強(qiáng)到弱為:銅鉑鈀三元合金銅鉑二元合金銅鈀二元合金。三元合金的高度合金化是引起高的氧氣還原和甲醇氧化的電催化性能的原因之一。
[Abstract]:In order to study the effect of the composition and alloying effect of Cu-base alloy nanotubes on their electrocatalytic properties, in this paper, copper nanowires were used as templates and electrochemical replacement method was used to synthesize copper nanotubes. Different kinds of copper-based multicomponent alloy nanotubes were prepared and their properties and mechanism of oxygen reduction were studied. Firstly, using chloroplatinic acid as platinum source and copper nanowires as precursor template, copper-platinum binary alloy nanotubes with different compositions were prepared by controlling the amount of chloroplatinic acid. The diameter of the nanotubes is between 100-150 nm, the wall thickness is 15-25 nm, the length of the nanotubes is 2-3 渭 m, and the copper and platinum elements are distributed uniformly on the alloy nanotubes. The electrocatalytic properties of copper platinum alloy nanotubes with different compositions were studied. Among them, the composition of Cu40Pt60 has the best catalytic performance. The initial potential and half-wave potential of the catalytic oxygen reduction reaction are higher than commercial Pt/C 57mV and 20mV, respectively. In the process of catalytic methanol oxidation, the ratio of positive and negative sweep peak current density is about 1.57 times of commercial Pt/C. The material alloying effect can greatly improve its electrocatalytic activity. The results of redox reaction show that the electronic structure of Pt 5d orbital is changed due to the effect of copper-platinum alloying in commercial Pt/C, copper-platinum alloys, which weakens the interaction between hydroxide and the surface of the alloy. The rate of electrocatalytic reaction was increased. Secondly, in order to reduce the cost of the binary alloy, palladium chloride was used to replace chloroplatinic acid, and copper alloy nanotubes were prepared by the same electrochemical replacement method. The results showed that the catalyst exhibited excellent catalytic performance of methanol oxidation, and most of the catalysts showed better catalytic performance than commercial Pt/C.. In order to further investigate the effect of alloying effect on catalytic performance, copper platinum-palladium ternary alloy nanotubes were prepared on the basis of the above binary alloys. In the ternary alloy nanotubes, all metal elements are uniformly distributed on the wall of the alloy nanotubes, and the alloying degree reaches the atomic level. The ternary alloys have excellent catalytic performance due to the synergistic effect between metals. The catalytic oxygen reduction performance of ternary alloys with different composition is superior to commercial Pt/C,. The best performance of Cu28.5Pt37.2Pd34.3, is that the initial potential and half wave potential of Cu28.5Pt37.2Pd34.3, in acid system are higher than commercial Pt/C 88mV and 49mV respectively. At the potential value of 0.85 V (vs.RHE), the kinetic current density of catalytic oxygen reduction is about 8 times that of commercial Pt/C. In addition, the ratio of positive and negative peak current density of methanol oxidation is about 1. 9 times that of commercial Pt/C. Finally, by comparing the performance of three kinds of alloy catalysts, the catalytic activity from strong to weak is as follows: copper-platinum-palladium ternary alloy copper-platinum binary alloy copper-palladium binary alloy. The high alloying of ternary alloys is one of the reasons for the high electrocatalytic properties of oxygen reduction and methanol oxidation.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TB383.1;O643.36

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