Rapid solution combustion synthesis of ordered mesoporous oxide films with tunable architectures: formation dynamics revealed by in situ GISAXS

Abstract

Mesoporous oxide films with high internal pore surface areas (often >300 m² g⁻¹) enable unique hybrid nanocomposites unlocking improvements for catalysis, energy storage, and sensing. However, rapid manufacturing methods for tunable oxide matrices with variable pore size, volume, surface chemistry, and shape remain elusive. Traditional synthetic paradigms for porous oxide film formation typically lack the scalability to easily generate variable pore geometries and require multi-hour aging and high-temperature (often >400 °C) sintering. Here, we significantly expand the porogen-integrated rapid oxidation (PiRO) method, which we previously reported for only close-packed alumina spheroidal pores, to achieve mesoporous oxides at temperatures <300 °C with diverse pore geometries (vertically oriented rods, worm-like channels, and closed-packed spheroids) and tunable pore diameters (6–15 nm). We expand the portfolio of available chemistries to mixed oxide phase (Li/Al, Ni/Al, and Cu/Al) previously difficult to attain with high throughput via sol–gel routes due to the varying cation hydrolysis rates. Scalable phosphonic acid surface treatments then modify the film surface contact angle from <5° to >80° for improving interactions with hydrophobic materials. Through a custom in situ GISAXS methodology, we elucidate thermal-initiated micellular phase transitions which dictate the final pore geometry and reveal real-time (50 ms frame rate) characterization of thin film combustion kinetics. Finally, we demonstrate filling of pores to generate an oxide/polymer composite. These advances position PiRO for targeted design of ordered mesoporous oxides for nanocomposite energy device applications.