La1-xCaxMnO3纳米颗粒的制备及氧还原催化性能

本文采用溶胶凝胶法制备了一系列不同Ca含量的钙钛矿型氧化物La1-xCaxMnO3(x=0~0.4)纳米颗粒,X射线粉末衍射及精修、扫描电镜表征显示其相纯度和结晶度高,颗粒平均粒径约40 nm。在0.1 mol.L-1KOH水溶液中进行的氧还原电催化性能测试显示,La0.7Ca0.3MnO3样品催化活性最高,表观电子转移数接近4,还原电流密度与Pt/C催化剂相当,而催化稳定性优于Pt/C。进一步研究了La1-xCaxMnO3样品中Mn价态、晶胞参数的改变对氧还原催化活性的影响,结果表明当x=0.3时,催化剂中Mn处于混合价态,Mn-O键长适中,最有利于电催化反应。

Sol-Gel Synthesis of Perovskite La1-xCaxMnO3(x=0~0.4) Nanoparticles for Electrocatalytic Oxygen Reduction

In this work, a series of La_1-xCa_xMnO₃ perovskite nanoparticles were prepared through a sol-gel method and investigated as catalysts for the oxygen reduction reaction (ORR). The XRD, SEM and TEM characterization demonstrated high crystallinity of the synthesized particles having diameters of about 40 nm. The crystal structure was determined by Rietveld refinement, indicating variation of the lattice parameters with the amount of substituted Ca. The electrocatalytic properties of the samples were studied using rotating-disk and rotating ring-disk electrode techniques in KOH aqueous solution. Investigations on the composition-performance relationship of La_1-xCa_xMnO₃ perovskites revealed that mixed Mn valence and medium Mn-O bond length favored the ORR electrocatalysis. Among the La_1-xCa_xMnO₃ series, La_0.7Ca_0.3MnO₃ exhibited outstanding ORR activity, enabled an apparent 4-electron pathway and showed superior durability compared to the benchmark carbon-supported Pt nanoparticles. Furthermore, metal-air cells assembled with La_0.7Ca_0.3MnO₃ could deliver high charge and discharge capacity with flat plateaus. The considerable catalytic performances of La_1-xCa_xMnO₃ nanoparticles indicate their promising application as low-cost and high-abundance catalysts in alkaline fuel cells and metal-air batteries.