Microcapsulation of phase change materials (PCMs) within a shell is one of the most feasible methods to explore their applications for thermal energy storage. Here, a facile method to microencapsulate PCMs within polystyrene/cellulose nanocrystal (CNC) hybrid shell via Pickering emulsion polymerization was developed. CNCs, as biobased and sustainable materials hydrolyzed from wood pulp, were employed as emulsifiers of the PCM Pickering emulsion and shell components of the PCM microcapsules as well. CNCs displayed a high efficiency in the stabilization of paraffin wax (PW) Pickering emulsion, and the heat capacity and stability of PW microcapsules with CNC shell (PW@CNC) increased dramatically with the amounts of CNCs. PW microcapsules with polystyrene and CNC hybrid shell (PW@PS/CNC) were prepared via Pickering emulsion polymerization of styrene from the CNC stabilized PW Pickering emulsion droplets. The PW@PS/CNC slurries possessed a latent heat capacity of 31.9 J/g with stability as high as 99.4% after 100 heating and cooling scans. The PW@PS/CNC powder possessed a latent heat capacity of 160.3 J/g, corresponding to a high encapsulation ratio of 83.5%. Moreover, coconut oil (CO), as an example of biobased PCMs, was also microencapsulated within polystyrene and CNC hybrid shell (CO@PS/CNC) via a similar method. Both PW@PS/CNC and CO@PS/CNC slurries displayed excellent temperature regulation ability and offered promising potentials for thermal energy storage systems.

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