NiCo-MOF、FeNi-MOF-5及其衍生磷化物的制备、表征和电解水活性的研究

发布时间：2018-04-28 09:24

  本文选题：MOFs + 双金属磷化物　； 参考：《北京化工大学》2017年硕士论文

【摘要】：金属-有机骨架材料(MOFs)是一种具有多孔结构的晶体复合材料,它由金属离子与有机官能团有序配位而成,具有永久的孔结构、大的比表面积、可调节的孔径尺寸等性质,以上特性使MOFs材料成为一种良好的模板化的复合材料。此外,金属离子与有机基团的多样性,使MOFs材料具有可调节的结构及元素组成。作为配体的有机官能团中含有丰富的C、N元素,根据报道,不同元素之间的掺杂作用会使材料的催化性能得以提高。过渡金属磷化物具有良好的导电性,是一种已报道的不含贵金属的电解水的催化剂,在OER和HER催化反应中得到广泛的应用。本课题目的在于利用MOFs材料作为模板剂,经过磷化反应制得相应的磷化物催化剂。本实验中首先利用水热法,以四水乙酸钴和乙酰丙酮镍为金属离子源、对苯二甲酸为配位剂、PVP为表面活性剂,在DMF和水的混合溶液中合成出了 NiCo-MOF材料。将制得的NiCo-MOF与NaH2PO2反应制得表面包覆一层碳膜的颗粒状的双金属磷化物Ni2P-CoP。在0.5M的H2SO4溶液中进行HER测试,过电势为-104mV,Tafel斜率为63mV/dec; 0.1M的KOH溶液进行OER活性测试,过电势为320 mV,Tafel斜率为63mV/dec,并且在HER和OER活性测试中,材料均具有很好的稳定性。通过面扫和HRTEM测试,发现材料中Ni、Co、P是均匀分布,并且Ni2P和CoP是紧密聚集在一起的。对比Ni2P-CoP、Ni2P、CoP、机械混合的 Ni2P+CoP 的 HER 和 OER 活性,发现Ni2P-CoP的电解水的活性最好,证明了 Ni2P-CoP中的协同作用促使其活性优于其他催化剂。本实验中,还制备了一种含有Fe、Ni元素的MOF-5材料。调节Fe、Ni元素的摩尔比,发现材料由立方块结构变成立方块8个角处长棒的复合结构,并且发现当Fe/Ni的值越大时棒越粗、数量越多。BET的测试结构显示当Fe/Ni为1:2时,材料具有最大的比表面积和平均孔径,分别为507.3 m2/g和14 nm,随着Fe/Ni的值变大材料的比表面积和平均孔径都下降。将制备的FeNi-MOF-5与NaH2P02在350 ℃下反应3 h,制得Fe、Ni的双金属磷化物,发现材料的形貌能够保存。在0.5M H2SO4的溶液中进行HER活性测试,当Fe/Ni为1:2时活性最好过电势为-254 mV,Tafel斜率为96 mV/dec。
[Abstract]:The metal-organic skeleton material (MOFs) is a kind of crystal composite with porous structure. It is composed of metal ions and organic functional groups, which have permanent pore structure, large specific surface area, adjustable pore size, etc. The above properties make MOFs material a good template composite material. In addition, the diversity of metal ions and organic groups makes MOFs materials have adjustable structure and elemental composition. The organic functional groups as ligands contain abundant Con N elements. According to the reports, doping among different elements will improve the catalytic performance of the materials. Transition metal phosphates have good electrical conductivity and are reported as catalysts for electrolytic water without precious metals. They have been widely used in the catalytic reactions of OER and HER. The purpose of this paper is to prepare phosphates catalyst by phosphating reaction using MOFs material as template. In this experiment, the NiCo-MOF materials were synthesized by hydrothermal method in the mixed solution of DMF and water with cobalt acetate and nickel acetylacetone tetrahydrate as metal ion source and terephthalic acid as coordination agent. The granular bimetallic phosphates Ni2P-CoP coated with a carbon film were prepared by the reaction of the prepared NiCo-MOF with NaH2PO2. The HER test was carried out in 0.5m H2SO4 solution, and the overpotential was -104mV / Tafel slope of 63mV / r, and the OER activity of 0.1M KOH solution was tested. The overpotential was 320mV / t Tafel slope of 63mV / r / decol.And in the HER and OER activity tests, the material had good stability. The results of surface scanning and HRTEM test show that NiCoP is uniformly distributed and that Ni2P and CoP are closely clustered together. Comparing the HER and OER activities of the mechanically mixed Ni2P CoP with Ni2P-CoP, it was found that the electrolysis water of Ni2P-CoP had the best activity, which proved that the synergistic action in Ni2P-CoP promoted its activity to be superior to that of other catalysts. In this experiment, we also prepared a kind of MOF-5 material containing Fe Ni. By adjusting the mole ratio of Fe ~ (2 +) Ni, we found that the material changed from a square structure to a composite structure with eight square angles. It was also found that the bigger the value of Fe/Ni, the thicker the rod, the more the number of Fe/Ni. The test structure showed that when Fe/Ni was 1:2, The material has the largest specific surface area and average pore size, which are 507.3 m2 / g and 14 nm, respectively. The specific surface area and average pore size of the material decrease with the increase of Fe/Ni value. Bimetallic phosphates were prepared by the reaction of FeNi-MOF-5 and NaH2P02 at 350 鈩，

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