MnO2 nanowires decorated with Au ultrasmall nanoparticles for the green oxidation of silanes and hydrogen production under ultralow loadings

Abstract

Although green catalytic transformations are very attractive, they often remain limited by low conversion percentages and selectivity. Here, we demonstrate that high catalytic performances (TOF=590,000h−1) could be achieved towards the green oxidation of silanes and H2 production under ultralow Au loadings (0.001–0.0002mol% in terms of Au) employing H2O as the oxidant, 25°C as the reaction temperature, and MnO2 nanowires decorated with ultrasmall Au NPs (3nm) as catalysts. In addition to these high activities towards a variety of substrates, the MnO2–Au NPs displayed good stability/recyclability, in which no morphological changes or loss of activity were observed even after 10 reaction cycles. The improved catalytic activities observed for the MnO2–Au NPs can be assigned to: (i) the metal–support interactions, in which the presence of Au NPs could facilitate oxidative processes and thus yield high performances towards the oxidation of hydrosilanes; (ii) the significant concentration of Auδ+ species and oxygen vacancies at the catalyst surface that represent highly catalytically active sites towards oxidation reactions, and (iii) the Au NPs ultrasmall sizes at the MnO2 surface that enable the exposure of high energy Au surface/facets, high surface-to-volume ratios, and their uniform dispersion. The MnO2–Au NPs could be synthesized by a facile approach based on the utilization of MnO2 nanowires as physical templates for Au deposition without any prior surface modification/functionalization steps. The utilization of supported ultrasmall Au NPs having controlled sizes and dispersion may inspire the design of novel catalysts capable of enabling high catalytic performances towards green transformations at ultralow metal loadings.