State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of Electrochemical Process and Technology for Materials, Beijing University of Chemical Technology , Beijing 100029, China.
ACS Appl Mater Interfaces. 2015 Dec 9;7(48):26914-22. doi: 10.1021/acsami.5b06100. Epub 2015 Nov 30.
Constructing nanoscale hybrid materials with unique interfacial structures by using various metal oxides and carbon supports as building blocks are of great importance to develop highly active, economical hybrid catalysts for oxygen reduction reaction (ORR). In this work, La2O2CO3 encapsulated La2O3 nanoparticles on a carbon black (La2O2CO3@La2O3/C) were fabricated via chemical precipitation in an aqueous solution containing different concentrations of cetyltrimethyl ammonium bromide (CTAB), followed by calcination at 750 °C. At a given CTAB concentration 24.8 mmol/L, the obtained lanthanum compound nanoparticles reach the smallest particle size (7.1 nm) and are well-dispersed on the carbon surface. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate the formation of La2O2CO3 located on the surface of La2O3 nanoparticles in the hybrid. The synthesized La2O2CO3@La2O3/C hybrid exhibits a significantly enhanced electrocatalytic activity in electrocatalysis experiments relative to pure La2O3, La2O2CO3, and carbon in an alkaline environment, by using the R(R)DE technique. Moreover, its long-term stability also outperforms that obtained by commercial Pt/C catalysts (E-TEK). The exact origin of the fast ORR kinetics is mainly ascribed to the La2O2CO3 layer sandwiched at the interface of carbon and La2O3, which contributes favorable surface-adsorbed hydroxide (-OH(-)(ad)) substitution and promotes active oxygen adsorption at the interfaces. The unique covalent -C-O-C(═O)-O-La-O- bonds, formed at the interfaces between La2O2CO3 and carbon, can act as active sites for the improved ORR kinetics over this hybrid catalyst. Therefore, the fabrication of lanthanum compound-based hybrid material with an unique interfacial structure maybe open a new way to develop carbon-supported metal oxides as next-generation of ORR catalysts.
通过使用各种金属氧化物和碳载体作为构建块来构建具有独特界面结构的纳米级混合材料，对于开发用于氧还原反应（ORR）的高活性、经济的混合催化剂非常重要。在这项工作中，通过在含有不同浓度十六烷基三甲基溴化铵（CTAB）的水溶液中进行化学沉淀，然后在 750°C 下煅烧，制备了 La2O2CO3 封装的 La2O3 纳米颗粒在碳黑上（La2O2CO3@La2O3/C）。在给定的 CTAB 浓度 24.8 mmol/L 下，获得的镧化合物纳米颗粒达到最小的粒径（7.1nm），并且在碳表面上很好地分散。X 射线衍射（XRD）和 X 射线光电子能谱（XPS）结果表明，在混合体中形成了位于 La2O3 纳米颗粒表面的 La2O2CO3。在碱性环境中，通过使用 R(R)DE 技术，相对于纯 La2O3、La2O2CO3 和碳，所合成的 La2O2CO3@La2O3/C 混合体在电催化实验中表现出显著增强的电催化活性。此外，其长期稳定性也优于商业 Pt/C 催化剂（E-TEK）。快速 ORR 动力学的确切起源主要归因于夹在碳和 La2O3 界面之间的 La2O2CO3 层，其有利于表面吸附的氢氧化物（-OH(-)(ad)）取代并促进活性氧在界面处的吸附。在 La2O2CO3 和碳之间的界面处形成的独特的共价 -C-O-C(═O)-O-La-O-键可以作为改善该混合催化剂的 ORR 动力学的活性位点。因此，具有独特界面结构的镧化合物基混合材料的制备可能为开发作为下一代 ORR 催化剂的碳负载金属氧化物开辟新途径。
