Incorporating Pb2+ Templates into the Crystalline Structure of MnO2 Catalyst Supported on Monolith: Applications in H2O2 Decomposition

Several MnO 2 catalysts, promoted with Pb 2+ ions and supported on a wash-coated monolith (WMon), briefly, x Pb y Mn-WMon ( x = 0, 0.5, 1.0, 1.5, 2, and 2.5 and y = 8 wt %), were prepared. The presence of Pb 2+ affects the manganese oxidation state, crystalline phase, thermal resistance, metal dispersion, and catalytic performance. According to XPS spectra, XRD patterns and HRTEM images, manganese was dispersed on the monolith surface as Mn 3+ and Mn 4+ species in both α and β crystalline phases. The ratios of Mn 4+ /Mn 3+ states and α / β phases were highly enhanced, and the desired Pb x Mn 8 O 16 phase (coronadite) was formed. Concentrations of the defect oxygen (Mn-O-H) and oxygen vacancies, which improve the catalyst reducibility and the MnO 2 reduction temperature, were also increased. Further, based on the H 2 chemisorption analysis, the Pb 2+ template would increase the manganese dispersion and the reaction sites. Meanwhile, the average MnO 2 crystallite size was decreased from 13.26 to 8.15 nm. The optimum catalyst 1.5Pb8Mn-WMon exhibited an activity 149% more than the manganese-only catalyst in decomposition of H 2 O 2 . Evaluation of catalyst stability in the presence of Pb 2+ after 10 recycles showed only a 6.8% decrease. The catalytic reaction was evaluated based on different criteria.