Salting-out and salting-in of protein: A novel approach toward fabrication of hierarchical porous carbon for energy storage application

Hierarchical porous carbon (HPC) materials have been synthesized via a combined freeze drying and carbonization process, that using egg white protein (EW-protein) as a precursor, NaCl as a template. Two competitive effects, salting out and salting in of EW-protein, were conveniently tuned by changing the NaCl concentrations, resulting in controllable hierarchical structures, surface areas and pore size distributions of HPC. The optimal product of HPC-4 displays a 3D honeycomb-like network (100–200 nm), inner cubic mesopores (20–50 nm) and high large surface area of 1745.64 m2 g−1. As an anode material of Li-ion battery, HPC-4 presents reversible capacity of 1131 mAh g−1 after 100 cycles at 0.2 A g−1, good rate capability, and a reversible capacity of 553 mA h g−1 after 1000 cycles at high current density of 10 A g−1. This work provides an environmentally friendly and low cost route to fabricate HPC with excellent electrochemical performances. [Display omitted] •EW-protein derived N-doped HPC by using NaCl as template.•Salting in and salting out of protein affect the pore structures of HPC.•HPC exhibits good electrochemical performance.•It's an environmentally friendly and low cost route to fabricate HPC.