Multifunctional, Highly Flexible, Free-Standing 3D Polypyrrole Foam

A multifunctional 3D PPy foam was fabricated by electropolymerizing Py onto nickel foam followed by the etching of the substrate. Porous NF with an interconnected 3D scaffold was chosen as the template for the electrodeposition of PPy. In brief, Py monomers were mixed with a NaClO₄ solution with a certain concentration in an electrolytic cell. After the NF was immersed into the solution, a layer of Py molecules were adsorbed on the nickel framework (Figure 1 a). Then, the Py monomers were crosslinked into a solid PPy film by electropolymerization in a three-electrode configuration with the nickel foam as the working electrode. In this way, a PPy@NF core?shell composite is obtained in which each nickel network unit was wrapped by a uniform PPy layer and the thickness of the PPy film can be adjusted by the deposition time. To obtain PF, the as-prepared PPy@NF composite was directly immersed into a FeCl₃ solution for several hours under room temperature to etch away the nickel substrate. The black PPy foam with a continuous and interconnected 3D network separates from the substrate and floats to the surface of the solution. After being coated with a layer of graphene, the 3D PPy@G foam exhibits enhanced performance due to the synergistic effect of PPy and graphene. The tensile strength of 3D PPy@G increases to 200 kPa and the specific capacitance is 702.9 F g^-1 when used as supercapacitor electrode, which is nearly two times that of 3D PPy electrode.