Enhanced MnO<sub>2</sub> Nanorods to CO and Volatile Organic Compounds Oxidative Activity by Platinum Nanoparticles

Abstract

Pure-phase α-MnO2 and δ-MnO2 nanorods were synthesized through an easy solution-based hydrothermal method. Platinum nanoparticles supported by the obtained MnO2 nanorods were prepared by the colloid deposition process. The microstructure and adsorption activity of the obtained catalysts were researched by different techniques such as transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption measurements, and H2 temperature-programmed reduction (H2-TPR). The cataluminescence (CTL) properties of CO and volatile organic compounds (VOCs), such as benzene and toluene, on the resultant catalysts were explored. The results showed that the platinum nanoparticles were well distributed in α-MnO2 and δ-MnO2. In addition, the Pt load process does not affect the crystal phase structure of the α-MnO2 nanorods, but can generate structural changes in the δ-MnO2 nanorods. The phase transformation did not the result of the reaction between the δ-MnO2 nanorods and Pt as shown in the XPS study. The α-MnO2 and δ-MnO2 nanorods showed a high catalytic oxidative activity toward CO, benzene, and toluene, and δ-MnO2 showed a higher activity than the α-MnO2 phase. Although, the Pt load led to a [Article] doi: 10.3866/PKU.WHXB201112082 www.whxb.pku.edu.cn 物理化学学报(Wuli Huaxue Xuebao) Acta Phys. -Chim. Sin. 2012, 28 (2), 437-444 February Received: September 29, 2011; Revised: December 1, 2011; Published on Web: December 8, 2011. ∗Corresponding authors. ZHU Yong-Fa, Email: zhuyf@tsinghua.edu.cn; Tel: +86-10-62787601. WU Xiao-Qin, Email: wxq968@sina.com; Tel: +86-791-83963377. The project was supported by the National Natural Science Foundation of China (20925725), National Key Basic Research Program of China (973) (2007CB613303), and Jiangxi Provincial Department of Education Technology Project, China (GJJ11507). 国家自然科学基金(20925725),国家重点基础研究发展规划项目(973) (2007CB613303)和江西省教育厅科技项目(GJJ11507)资助 C Editorial office of Acta Physico-Chimica Sinica Pure-phase α-MnO2 and δ-MnO2 nanorods were synthesized through an easy solution-based hydrothermal method. Platinum nanoparticles that are supported by the obtained MnO2 nanorods were prepared by the colloid deposition process. The microstructure and adsorption activity of the obtained catalysts were researched by different techniques such as transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption measurements, and H2 temperature-programmed reduction (H2-TPR). The cataluminescence (CTL) properties of CO and volatile organic compounds (VOCs), such as benzene and toluene, on the resultant catalysts were explored. The results showed that the platinum nanoparticles are well distributed in α-MnO2 and δ-MnO2. In addition, the Pt load process does not affect the crystal phase structure of the α-MnO2 nanorods, but can generate structural changes in the δ-MnO2 nanorods. The phase transformation did not the result of the reaction between the δ-MnO2 nanorods and Pt as shown in the XPS study. The α-MnO2 and δ-MnO2 nanorods show a high catalytic oxidative activity toward CO, benzene, and toluene, and δ-MnO2 showed a higher activity than the α-MnO2 phase. Although, the Pt load leads to a decrease in the surface area of the MnO2 nanorods were confirmed by the N2 adsorption-desorption measurements, but the H2-TPR results shows the interaction between Pt and MnO2 is intense, which significantly enhanced its catalytic activity. The Pt/δ-MnO2 nanorods exhibited a higher activity than Pt/α-MnO2. CTL research shows that the activities of the four catalysts increased in the order of α-MnO2≤δ-MnO2 <Pt/α-MnO2<Pt/δ-MnO2, and the H2-TPR results are consistent. Pt loading significantly enhanced the catalytic oxidative activity of α-MnO2 and δ-MnO2 nanorods to CO, benzene, and toluene. 437 Acta Phys. -Chim. Sin. 2012 Vol.28 decrease in the surface area of the MnO2 nanorods which was confirmed by the N2 adsorption-desorption measurements, but the H2-TPR results showed that the interaction between Pt and MnO2 was intense, which significantly enhanced its catalytic activity. The Pt/δ-MnO2 nanorods exhibited a higher activity than Pt/α-MnO2. CTL research showed that the activities of the four catalysts increased in the order of α-MnO2≤ δ-MnO2<Pt/α-MnO2<Pt/δ-MnO2, and the H2-TPR results were consistent. Pt loading significantly enhanced the catalytic oxidative activity of α-MnO2 and δ-MnO2 nanorods to CO, benzene, and toluene.