碳载NiCu@Pd纳米核壳催化剂的制备及其电化学性能研究

发布时间：2018-03-03 00:33

本文选题：氧化铝工艺　切入点：碱溶碳分法　出处：《北京化工大学》2015年硕士论文　论文类型：学位论文

【摘要】：碱溶碳分法氧化铝生产工艺是一种突破传统拜耳法的高效新工艺,其关键技术是膜电解碳酸钠溶液获得碳酸氢钠和氢氧化钠。现有膜电解碳酸钠技术采用析氢阴极和析氧阳极,槽压为2.5-2.6 V,电耗高达1800～1900 kWh/t Al2O3,为大幅度降低电耗,本课题组提出以氢阳极替代析氧阳极,并且将阴极产生的氢气导入阳极,形成氢循环利用的节能电解技术方案。其中,研究出一种高性能的氢阳极催化剂是高效节电的氢循环电解的关键所在。本文研究设计了一类以NiCu合金为核,Pd为壳层的碳载NiCu@Pd纳米核壳结构的氢阳极催化剂。采用热还原法制备NiCu/C,通过乙二醇还原的方法在NiCu合金上负载Pd合成NiCu@Pd/C催化剂。主要考察NiCu合金的含量,Ni/Cu的比例,Pd的载量以及制备过程对催化剂形貌、纳米结构、微观组分的影响机制,以及对催化剂电催化氢气氧化动力学,抗中毒能力,寿命等的影响规律。XRD分析表明NiCu合金的含量,Ni/Cu的比例,Pd的载量均对外层Pd原子的晶格间距有着显著的影响。TEM图像表明Ni1Cu4@Pd/C催化剂的粒径为6.8±1.2 nm,且粒径分布均匀。电化学测试表明NiCu@Pd/C催化剂的氢氧化性能受到晶格间距和电子效应的共同影响。综合考虑,NiCu合金含量为20%,前驱体Ni/Cu比例为1：4,Pd的载量为10%时,该催化剂显示出了最优的氢氧化性能。相比于载量为20%的Pd/C的催化剂,该催化剂不仅在氢氧化性能方面大大优于20%Pd/C,同时其抗甲醇中毒能力也超过20% Pd/C。这主要是因为由于内核NiCu金属与贵金属之间的相互作用,导致贵金属晶格间距的收缩。这样的配位效应使得贵金属d轨道重叠增加,d能带中心下降。另外,NiCu与贵金属Pd之间相互作用使得贵金属上的d轨道电子云密度降低。贵金属Pd的d能带中心的下降和d轨道电子云密度降低使得其与中间产物(COads)的作用大大降低,避免了活性位的中毒。将上述Ni1Cu4@Pd/C为催化剂的的气体扩散氢阳极,在应用于氢阳极电解碳酸钠的电解时展现出了非常的低的槽压和突出的节能优势。在10 mA·cm-2的电流密度下,槽压仅仅为0.44 V。在100 mA·cm-2的电流密度下,相比于Pd/C氢阳极电解1.38 V的槽压和传统电解2.53 V的槽压,Ni1Cu4@Pd/C氢阳极电解碳酸钠的槽压可降低至1.09 V,相当于电解电耗约800 kWh/t Al2O3,相比常规电解节电57%,具有显著的节电节能意义。
[Abstract]:The alkali soluble carbon process for alumina production is a breakthrough in the traditional new efficient process with Bayer method, the key technology is membrane electrolytic solution of sodium carbonate to obtain sodium bicarbonate and sodium hydroxide. The existing membrane electrolysis of sodium carbonate by hydrogen evolution and oxygen evolution anode, tank pressure is 2.5-2.6 V, power consumption of up to 1800~1900 kWh/t for Al2O3 greatly reduce the power consumption, the research group proposed to replace the hydrogen anode anode, and the hydrogen into the anode and cathode of the formation of the program, energy recycling hydrogen electrolysis technology. The research of a high performance hydrogen anode catalyst is high efficiency electrolytic hydrogen cycle is the key. This paper studies the design a class of NiCu alloy as anode catalyst for hydrogen nuclei, Pd shell carbon nano NiCu@Pd core-shell structure. The preparation of NiCu/C by thermal reduction method, Pd method by ethylene glycol reduction of negative in NiCu alloy The NiCu@Pd/C content of catalyst. Mainly on the NiCu alloy, the ratio of Ni/Cu, Pd load and the preparation process of the catalyst morphology, nano structure, the influence mechanism of micro components, as well as the catalyst electrocatalytic hydrogen oxidation kinetics, anti poisoning ability,.XRD influence life analysis showed that the content of NiCu alloy, Ni/Cu the proportion of the Pd load are outer layer Pd atoms with lattice spacing of.TEM images are significantly affected that of Ni1Cu4@Pd/C catalyst particle size of 6.8 + 1.2 nm, and homogeneous particle size distribution. The electrochemical test shows that hydrogen oxidation performance of NiCu@Pd/C catalyst is influenced by lattice spacing and electron effect. Considering NiCu alloy the content is 20%, the precursor Ni/Cu ratio of 1:4, the Pd load is 10%, the catalyst showed hydrogen oxidation. Compared to the optimal performance of the load of 20% Pd/C catalyst, the catalyst not only Much better than the hydrogen oxidation performance of 20%Pd/C, and its anti methanol poisoning capacity than 20% Pd/C. this is mainly because the interaction between the kernel NiCu metal and precious metals, precious metals lead to contraction of the lattice spacing. Such coordination effect makes the noble metal d orbitals overlap, d band center also decreased. And the interaction between NiCu and noble metal Pd makes d orbital electron cloud density on the precious metals decreased. Noble metal Pd d band center declined and d orbital electron density lower with the intermediate product (COads) greatly reduced the effect of the active sites, to avoid poisoning. The Ni1Cu4@Pd/C catalyst for gas the diffusion of hydrogen in the anode used in hydrogen anode electrolysis of sodium carbonate showed a very low pressure trough and prominent energy-saving advantages. At a current density of 10 mA - cm-2, the tank pressure is only 0.44 V. at 100 m The current density of A - cm-2, the tank pressure and the traditional electrolysis groove of 2.53 V compared to 1.38 V Pd/C hydrogen anode voltage, anode electrolytic hydrogen Ni1Cu4@Pd/C sodium carbonate cell voltage can be decreased to 1.09 V, equivalent to the electrolytic power consumption of about 800 kWh/t Al2O3, compared with conventional electrolytic power saving of 57% has significant energy saving.

【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ133.1;O643.36

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