Shellac derived graphene films on solid, flexible, and porous substrates for high performance bipolar plates and supercapacitor electrodes

Here, we report the growth of improved quality graphene thin film by a modified method using shellac as a low-cost and eco-friendly carbon source on three different substrates. We chose stainless steel (SS 316) plates used as a solid surface, nickel foam (NiF) representative of a solid porous substrate, and carbon fiber fabric (CFF) as a porous-flexible substrate. The graphene characteristic is found to be substrate-dependent in this single-step method. Uniform multilayer graphene is grown on SS316. In the case of Ni foam, the as-synthesized graphene exhibits high quality with relatively low defects. It was troublesome to grow uniform graphene on flexible CFF due to the low wettability of precursor solution. The substrate was required to modify with a thin (∼60 nm) layer of Ni deposition. The transfer-free method of graphene on CFF was assured by etching Ni via an acid treatment. Graphene coated SS316 used as bipolar plate exhibits superior corrosion resistance with corrosion current density Icorr ∼1.2 μA/cm2 and much lower interfacial contact resistance ICR ∼7.7 mΩ cm2. Graphene coated Ni foam was utilized as electrodes in supercapacitors which show large areal capacitance ∼1.7 F/cm2. Besides, graphene coated CFF shows sheet resistance ∼50% lower than that of uncoated CFF.