Flores-Lasluisa Jhony Xavier, Carré Bryan, Caucheteux Joachim, Compère Philippe, Léonard Alexandre F, Job Nathalie
Department of Chemical Engineering-NCE (Nanomaterials, Catalysis, Electrochemistry), University of Liège, B6a, Allée du Six Août 13, 4000 Liège, Belgium.
Center for Applied Research and Education in Microscopy (CAREM), Chemistry Institute, University of Liège, B6c, Allée du Six Août 11, 4000 Liège, Belgium.
Nanomaterials (Basel). 2024 Aug 19;14(16):1362. doi: 10.3390/nano14161362.
Metal oxides containing La, Mn, and Co cations can catalyze oxygen reduction reactions (ORRs) in electrochemical processes. However, these materials require carbon support and optimal interactions between both compounds to be active. In this work, two approaches to prepare composites of La-Mn-Co-based compounds over carbon xerogel were developed. Using sol-gel methods, either the metal-based material was deposited on the existing carbon xerogel or vice versa. The metal oxide selected was the LaMnCoO perovskite, which has good catalytic behavior and selectivity towards direct ORRs. All the as-prepared composites were tested for ORRs in alkaline liquid electrolytes and characterized by diverse physicochemical techniques such as XRD, XPS, SEM, or N adsorption. Although the perovskite structure either decomposed or failed to form using those in situ methods, the materials exhibited great catalytic activity, which can be ascribed to the strengthening of the interactions between oxides and the carbon support via C-O-M covalent bonds and to the formation of new active sites such as the MnO/Co heterointerfaces. Moreover, Co-N-C species are formed during the synthesis of the metal compounds over the carbon xerogel. These species possess a strong catalytic activity towards ORR. Therefore, the composites formed by synthesizing metal compounds over the carbon xerogel exhibit the best performance in the ORR, which can be ascribed to the presence of the MnO/Co heterointerfaces and Co-N-C species and the strong interactions between both compounds. Moreover, the small nanoparticle size leads to a higher number of active sites available for the reaction.
含有镧、锰和钴阳离子的金属氧化物可在电化学过程中催化氧还原反应（ORR）。然而，这些材料需要碳载体以及两种化合物之间的最佳相互作用才能具有活性。在这项工作中，开发了两种在碳干凝胶上制备镧 - 锰 - 钴基化合物复合材料的方法。使用溶胶 - 凝胶法，要么将金属基材料沉积在现有的碳干凝胶上，要么反之。所选的金属氧化物是具有良好催化行为和对直接ORR选择性的LaMnCoO钙钛矿。所有制备的复合材料都在碱性液体电解质中进行了ORR测试，并通过多种物理化学技术进行了表征，如XRD、XPS、SEM或N吸附。尽管使用那些原位方法钙钛矿结构要么分解要么未能形成，但这些材料表现出了很大的催化活性，这可归因于通过C - O - M共价键增强了氧化物与碳载体之间的相互作用以及形成了新的活性位点，如MnO/Co异质界面。此外，在碳干凝胶上合成金属化合物的过程中形成了Co - N - C物种。这些物种对ORR具有很强的催化活性。因此，通过在碳干凝胶上合成金属化合物形成的复合材料在ORR中表现出最佳性能，这可归因于MnO/Co异质界面和Co - N - C物种的存在以及两种化合物之间的强相互作用。此外，小的纳米颗粒尺寸导致可用于反应的活性位点数量更多。
