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 1745.64m(2) 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. (C) 2019 Elsevier B.V. All rights reserved.