ALBERT

Description: 〈p〉Publication date: 5 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Catalysis B: Environmental, Volume 244〈/p〉 〈p〉Author(s): Ke Li, Rongrong Zhang, Ruijie Gao, Guo-Qiang Shen, Lun Pan, Yunduo Yao, Kaihui Yu, Xiangwen Zhang, Ji-Jun Zou〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Manganese-cobalt spinel oxides are considered as a class of promising and low-cost electrocatalysts for oxygen reduction reaction (ORR), whose performances largely depend on their electronic structures which can be effectively optimized by defect engineering. Herein, metal defects (manganese vacancies and cobalt vacancies, 〈em〉i.e.〈/em〉 V〈sub〉Mn〈/sub〉 and V〈sub〉Co〈/sub〉) were 〈em〉in-situ〈/em〉 introduced into spinel Mn〈sub〉x〈/sub〉Co〈sub〉3-x〈/sub〉O〈sub〉4〈/sub〉〈em〉via〈/em〉 a simple solvothermal treatment followed by thermal calcination. Mn-Co glycerolate precursors not only enable controllable synthesis of spinel oxides with variable metallic ratios, but also play a key role in constructing metal defected crystals for their lamellated structure. As a result of the formation rate difference between manganese and cobalt glycerolate, a unique Mn-enriched surface is formed, leading to the increase of highly active sites for ORR. Importantly, the presence of metal defects, confirmed by XRD (X-ray diffraction), element analysis and XAFS (X-ray absorption fine structure spectroscopy), leads to greatly increased electrical conductivity and O〈sub〉2〈/sub〉 adsorption ability, thus bringing about enhanced ORR activity. Especially, metal-defected Mn〈sub〉1.5〈/sub〉Co〈sub〉1.5〈/sub〉O〈sub〉4〈/sub〉, with the optimal Mn/Co ratio, exhibits comparable activity and superior durability to those of the benchmark Pt/C in ORR and displays excellent discharge performance in Zn-air batteries for practical application. This work provides a new way to optimize the electrocatalytic performance of mixed metal spinel oxides 〈em〉via〈/em〉 rational defect engineering.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0926337318311305-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉