Water-Mediated Conversion of BaTiO₃ Nanoparticles into BaCO₃ Nanorods in Electrospun Polymer Fibers: Implications for Carbon Capture Applications

Under ambient conditions and in aqueous environments, transformations of nanoparticle-based ferroelectric components can raise important stability issues that are relevant for applications as multilayer capacitors, flexible piezoelectrics, or biomedical devices. We show that X-ray amorphous BaTiO₃ nanoparticles that were grown by flame spray pyrolysis and which can be incorporated into electrospun polymer fibers undergo incongruent Ba²⁺ dissolution in the presence of water. At pH > 5 and in contact with air, corresponding Ba solutes spontaneously convert into crystalline BaCO₃ needles to produce characteristic nano- and microstructures. We compared the reactivity of amorphous BaTiO₃ nanoparticle powders with those of nanocrystals after annealing-induced crystallization. The stability of aqueous nanoparticle–polymer formulations, which are typically part of nanoparticle encapsulation in polymers and electrospinning, was included in this analysis. Nanoparticle size, crystallinity, surface area, the presence of carbonaceous surface contaminants, and the effect of surface passivation with polymers are addressed to underline the critical role of condensed water during the synthesis, storage, and processing of BaTiO₃ nanoparticle-based composites.