Rapid Joule Heating-Induced Structural Evolution of Nonstoichiometric Ordered Mesoporous Aluminum-Based Spinel Structures

Coupling self-assembly with ultrashort transient heating at high temperatures effectively accelerates reaction kinetics through enhanced transformation pathways. This approach provides precise control over crystalline phase characteristics and enables emergent collective properties and functionalities in mesoporous inorganic materials. Here, we describe the structural evolution and rapid formation of highly crystalline, well-ordered mesoporous magnesium aluminate defect spinel structures with nonstoichiometric compositions, achieved in seconds via block copolymer-directed self-assembly and Joule heating. Isothermal experiments conducted ex situ demonstrated Joule heating-induced acceleration of the amorphous-to-spinel transition. The process aligned with the Johnson-Mehl-Kolmogorov-Avrami model, revealing an instantaneous surface nucleation and diffusion-controlled growth mechanism requiring significantly lower activation energy compared to conventional thermal treatments. Further exploration of the ultrafast approach led to the development of an ordered mesoporous defect spinel-carbon framework decorated with in situ crystallized platinum nanoparticles. This composite structure exhibited enhanced thermal and mechanical stability under high temperature reducing environments, demonstrating its potential for thermal catalytic applications. Understanding Joule heating-induced crystallization kinetics and phase transformations on transient timescales may reveal novel crystalline phases and functionalities inaccessible through conventional heating of nonstoichiometric compositions.