Magnetic field-assisted acceleration of energy storage based on microencapsulation of phase change material with CaCO3/Fe3O4 composite shell

Energy conversion and storage are crucial for overcoming energy-shortage problems. Herein, we designed and synthesized a type of magnetic phase-change microcapsule system for enhancing solar light-to-heat conversion efficiency through the synergetic conversion of photothermal and magnetocaloric energy. This microcapsule system was based on an n-eicosane core and a Fe3O4/CaCO3 composite shell and fabricated by means of a Pickering emulsion-templated in-situ precipitation technique. The composite microcapsules so obtained exhibit a regular spherical morphology and a well-defined core–shell microstructure, together with the desired chemical compositions and magnetic characteristics. The introduction of Fe3O4 nanoparticles enhanced the stability of the emulsion-templating system, resulting in an improvement in the phase-change enthalpies of the resultant composite microcapsules. Moreover, the presence of Fe3O4 nanoparticles endowed the microcapsule system with magnetic characteristics to realize a photothermal and magnetocaloric synergetic conversion. The composite microcapsules achieved a satisfactory latent-heat capacity of over 110 J/g and high photothermal conversion efficiency of 86.4%. More importantly, the composite microcapsules developed in this work presented a remarkable accelerated period of energy storage by 47.5% under an alternating magnetic field compared to those without an applied magnetic field. This study provides a promising approach for the design and development of phase-change microcapsules with a magnetism-accelerated energy conversion capability for efficient utilization of solar energy.