A solid with a hierarchical tetramodal micro-meso-macro pore size distribution

Abstract

Porous solids have an important role in addressing some of the major energy-related problems facing society. Here we describe a porous solid, alpha-MnO2, with a hierarchical tetramodal pore size distribution spanning the micro-, meso-and macro pore range, centred at 0.48, 4.0, 18 and 70 nm. The hierarchical tetramodal structure is generated by the presence of potassium ions in the precursor solution within the channels of the porous silica template; the size of the potassium ion templates the microporosity of alpha-MnO2, whereas their reactivity with silica leads to larger mesopores and macroporosity, without destroying the mesostructure of the template. The hierarchical tetramodal pore size distribution influences the properties of alpha-MnO2 as a cathode in lithium batteries and as a catalyst, changing the behaviour, compared with its counterparts with only micropores or bimodal micro/mesopores. The approach has been extended to the preparation of LiMn2O4 with a hierarchical pore structure.