Metal-free multiporous carbon for electrochemical energy storage and electrocatalysis applications

Abstract

Functionalized activated carbon materials are promising metal-free electrocatalysts for low-cost and environmentally benign efficient hydrogen evolution (HER) and oxygen evolution (OER) reactions. The use of rational design and optimized architectures are effective ways to produce numerous catalytic active sites, fast electron/ion movement, and better adsorption capabilities towards reactants. Here, we report a hierarchical multiporous honeycomb carbon network derived from naturally nitrogen enriched broccoli stem biomass and we have extended its application to a flexible wire supercapacitor as well as an efficient OER and HER electrocatalyst. We have achieved the lowest overpotential of 184 mV (vs. reversible hydrogen electrode) for the HER at a current density of 10 mA cm⁻², and 301 mV (vs. reversible hydrogen electrode) for the OER, comparatively much better than metal-doped carbon electrocatalysts. The flexible wire supercapacitor achieved an energy density of 3 W h kg⁻¹ at a power density of 450 W kg⁻¹ and a gravimetric specific capacitance of 106 F g⁻¹ at a current rate of 0.5 A g⁻¹.