Amphiphilic block copolymers directed synthesis of mesoporous nickel-based oxides with bimodal mesopores and nanocrystal-assembled walls

Abstract

Mesoporous late-transition metal oxides have great potential in applications of energy, catalysis and chemical sensing due to their unique physical and chemical properties. However, their synthesis via the flexible and scalable soft-template method remain a great challenge, due to the weak organic-inorganic interaction between the frequently used surfactants (e.g., Pluronic-type block copolymers) and metal oxide precursors, and the low crystallization temperature of metal oxides. In this study, ordered mesoporous NiO with dual mesopores, high surface area and well-interconnected crystalline porous frameworks have been successfully synthesized via the facile solvent evaporation-induced co-assembly (EICA) method, by using lab-made amphiphilic diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) as both the structure-directing agent (the soft template) and macromolecular chelating agents for nickel species, THF as the solvent, and nickel acetylacetonate (Ni(acac)2) as inorganic precursor. Similarly, by using Ni(acac)2 and Fe(acac)3 as the binary precursors, ordered mesoporous Fe-doped NiO materials can be obtained, which have bimodal mesopores of large mesopores (32.5 nm) and secondary mesopores (4.0–11.5 nm) in the nanocrystal-assembled walls, high specific surface areas (∼74.8 m2/g) and large pore value (∼0.167 cm3/g). The obtained mesoporous Fe-doped NiO based gas sensor showed superior ethanol sensing performances with good sensitivity, high selectivity and fast response-recovery dynamics.