Hydrophilic polymer foam and microsphere templates for fabrication of microcellular nickel and graphene foams with energy storage applications
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Hydrophilic polymer foam and microsphere templates have attracted tremendous attentions in the past decade due to their applicability in numerous areas such as catalyst carriers and mini-reactors, filtration media, carbon foam fabrication templates, thermal and electrical insulators, and tissue engineering scaffolds. Hydrophilic polymer sphere and foam templates can be used to fabricate microcellular nickel foams and graphene foams that are finding unique opportunities in energy storage applications, including battery electrodes and matrices for solar energy storage. In this study open celled hydrophilic polymer foams and microsphere templates with controllable pore size and porosity were fabricated via solid state foaming and vacuum-assisted assembling methods. Hydrophilic polymer foams were fabricated with disulfonated poly(arylene ether sulfone) (BPS) and poly(ethylene glycol) (PEG) miscible blends. Polymer microsphere templates made with PMMA, paraffin, and EAA spheres were used as templates for fabricating bulk nickel foams, which were further used as a template to fabricate graphene foams. In order to achieve bulk microcellular nickel and graphene foams, a novel electro-polishing-assisted electroless nickel (Ni) deposition process was developed to mitigate the diffusion limitation problem. Fundamental mechanisms of the proposed process were studied using a finite difference model considering both ion diffusion and chemical reaction inside the porous media. The fabricated microcellular Ni foams exhibited sufficient thermal stability and were used to fabricate three dimensional (3D) few-layer-graphene (FLG) foams using a chemical vapor deposition (CVD) method. The resulting graphene foams had a pore size less than 100 μm, density of 0.0020 g·cm⁻³, and strut wall thickness of 5 nm. The surface-to-volume ratio of the foam was 2.5×10⁵ m²·m⁻³.