Ghezali Nawel, Díaz Verde Álvaro, Illán Gómez María José
MCMA Group, Inorganic Chemistry Department, Materials Institute of the University of Alicante (IUMA), Faculty of Sciences, University of Alicante, 03690 Alicante, Spain.
Molecules. 2024 Feb 28;29(5):1056. doi: 10.3390/molecules29051056.
The sol-gel method, adapted to aqueous media, was used for the synthesis of BaMnCuO (BMC) and BaAMnCuO (BMC-A, A = Ce, La or Mg) perovskite-type mixed oxides. These samples were fully characterized by ICP-OES, XRD, XPS, H-TPR, BET, and O-TPD and, subsequently, they were evaluated as catalysts for CO oxidation under different conditions simulating that found in cars exhaust. The characterization results show that after the partial replacement of Ba by A metal in BMC perovskite: (i) a fraction of the polytype structure was converted to the hexagonal BaMnO perovskite structure, (ii) A metal used as dopant was incorporated into the lattice of the perovskite, (iii) oxygen vacancies existed on the surface of samples, and iv) Mn(IV) and Mn(III) coexisted on the surface and in the bulk, with Mn(IV) being the main oxidation state on the surface. In the three reactant atmospheres used, all samples catalysed the CO to CO oxidation reaction, showing better performances after the addition of A metal and for reactant mixtures with low CO/O ratios. BMC-Ce was the most active catalyst because it combined the highest reducibility and oxygen mobility, the presence of copper and of oxygen vacancies on the surface, the contribution of the Ce(IV)/Ce(III) redox pair, and a high proportion of surface and bulk Mn(IV). At 200 °C and in the 0.1% CO + 10% O reactant gas mixture, the CO conversion using BMC-Ce was very similar to the achieved with a 1% Pt/AlO (Pt-Al) reference catalyst.
采用适用于水相介质的溶胶-凝胶法合成了钙钛矿型混合氧化物BaMnCuO（BMC）和BaAMnCuO（BMC-A，A = Ce、La或Mg）。通过电感耦合等离子体发射光谱法（ICP-OES）、X射线衍射（XRD）、X射线光电子能谱（XPS）、程序升温还原（H-TPR）、比表面积分析（BET）和程序升温脱附（O-TPD）对这些样品进行了全面表征，随后，在模拟汽车尾气的不同条件下对它们作为CO氧化催化剂的性能进行了评估。表征结果表明，在BMC钙钛矿中用A金属部分替代Ba后：（i）部分多型结构转变为六方BaMnO钙钛矿结构；（ii）用作掺杂剂的A金属掺入到钙钛矿晶格中；（iii）样品表面存在氧空位；（iv）表面和体相中Mn(IV)和Mn(III)共存，表面上以Mn(IV)为主氧化态。在所用的三种反应气氛中，所有样品都催化了CO到CO₂的氧化反应，添加A金属后以及对于低CO/O比的反应混合物表现出更好的性能。BMC-Ce是最活跃的催化剂，因为它兼具最高的还原性和氧迁移率、表面存在铜和氧空位、Ce(IV)/Ce(III)氧化还原对的贡献以及高比例的表面和体相Mn(IV)。在200℃和0.1% CO + 10% O₂的反应气体混合物中，使用BMC-Ce的CO转化率与1% Pt/Al₂O₃（Pt-Al）参比催化剂所达到的转化率非常相似。
