MnO2 shape dependent catalytic activity in vapour phase benzyl alcohol (BnOH) oxidation in presence of air

Abstract

Understanding the relationship between the structure and the activity of the catalyst relies on the shape–controlled synthesis of nanostructures is crucial importance. The vapor phase oxidation of benzyl alcohol (BnOH) process over morphologically designed shape–selective manganese oxide nanorods (MnO2NR) and nanospheres (MnO2NS) catalysts are studied. The key catalytic properties are determined and demonstrated by various characterisation techniques such as P–XRD, BET, H2–TPR, O2–TPD, and Raman analysis. In addition, EDX and STEM–HRTEM microscopic analysis were carried out in better understanding the surface morphology, shape, and structure of the nanocatalysts. The prepared nanoporous MnO2NS catalyst enabled to generate more crystal defects, high surface area, strong reducing capacity, enhanced oxygen vacancies (Ov), and increased reactive surface oxygen species compared to nanorod shaped–MnO2NR catalyst. Significantly the rate of benzaldehyde (BnZA) formation in BnOH oxidation reaction over MnO2NS catalyst is ∼ 1.55 times higher than that of MnO2NR. Over MnO2NS creation of abundant O vacancies considerably improved the capacity of oxygen activation and redox ability. Thus, as a result, there are more active oxygen species which are mobile and reactive in accelerating the BnOH oxidation process.