State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology , No. 15 Beisanhuan East Road, Beijing 100029, China.
New Energy Research Institute, School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Center , Guangzhou, Guangdong 510006, China.
ACS Appl Mater Interfaces. 2017 Jan 25;9(3):2541-2549. doi: 10.1021/acsami.6b14942. Epub 2017 Jan 11.
A metal organic framework (MOF), synthesized from cobalt salt, melamine (mela), and 1,4-dicarboxybezene (BDC), was used as precursor to prepare Co/CoN/N-CNT/C electrocatalyst via heat treatment at different temperature (700-900 °C) under nitrogen atmosphere. Crystallites size and microstrain in the 800 °C heat-treated sample (MOFs-800) were the lowest, whereas the stacking fault value was the highest among the rest of the homemade samples, as attested to by the Williamson-Hall analysis, hence assessing that the structural or/and surface modification of Co nanoparticles (NPs), found in MOFs-800, was different from that in other samples. CNTs in MOFs-800, interacting with Co NPs, were formed on the surface of the support, keeping the hexagonal shape of the initial MOF. Among the three homemade samples, the MOF-800 sample, with the best electrocatalytic performance toward oxygen reduction reaction (ORR) in 0.1 M KOH solution, showed the highest density of CNTs skin on the support, the lowest I/I ratio, and the largest N atomic content in form of pyridinic-N, CoN, pyrrolic-N, graphitic-N, and oxidized-N species. Based on the binding energy shift toward lower energies, a strong interaction between the active site and the support was identified for MOFs-800 sample. The number of electron transfer was 3.8 on MOFs-800, close to the value of 4.0 determined on the Pt/C benchmark, thus implying a fast and efficient multielectron reduction of molecular oxygen on CoN active sites. In addition, the chronoamperometric response within 24 000 s showed a more stable current density at 0.69 V/RHE on MOFs-800 as compared with that of Pt/C.
一种由钴盐、三聚氰胺（mela）和 1,4-二羧酸苯（BDC）合成的金属有机骨架（MOF），在氮气气氛下于不同温度（700-900°C）下热处理，用作制备 Co/CoN/N-CNT/C 电催化剂的前驱体。在其余自制样品中，800°C 热处理样品（MOFs-800）的晶粒尺寸和微观应变最小，而堆垛层错值最高，这归因于威廉姆森-霍尔分析，因此评估 Co 纳米颗粒（NPs）的结构或/和表面改性在 MOFs-800 中与其他样品不同。MOFs-800 中的 CNTs 与 Co NPs 相互作用，在载体表面形成，保持初始 MOF 的六方形状。在三个自制样品中，对在 0.1 M KOH 溶液中氧还原反应（ORR）具有最佳电催化性能的 MOF-800 样品，显示出载体上 CNTs 皮层密度最高、I/I 比值最低、吡啶-N、CoN、吡咯-N、石墨-N 和氧化-N 物种中 N 原子含量最大。基于结合能向较低能量的移动，鉴定出 MOFs-800 样品中活性位点与载体之间的强相互作用。MOFs-800 的电子转移数为 3.8，接近在 Pt/C 基准上确定的 4.0 值，这意味着在 CoN 活性位点上分子氧的快速和有效的多电子还原。此外，在 24,000 s 内的计时安培响应中，与 Pt/C 相比，MOFs-800 上在 0.69 V/RHE 时的电流密度更稳定。
