Biowaste derived porous carbon sponge for high performance supercapacitors

Here,an agricultural waste(the stem pith of helianthus annuus,SPHA)is firstly used as the precursor for preparing three-dimensional(3D)porous carbon sponge(PCS).The as-prepared 3D PCS(SPHA-700)possesses unique sponge-like structure,large specific surface area(SSA)and high nitrogen doping level(4.52 at.%),which benefit the enhancement of conductivity(5.8 S cm;)and wettability.As a binder-free electrode for solid-state symmetric supercapacitor,SPHA-700 delivers a relatively high specific capacitance of137.1 F g^(-1)at 0.5 Ag^(-1).Moreover,activated SPHA-700(SPHA-ac-700–2)displays an even higher specific capacitance(403.6 F g^(-1)at 0.5 Ag^(-1))in 6.0 M KOH electrolyte.The SPHA-ac-700–2-based symmetrical supercapacitor can offer high specific capacitance(271 F g^(-1)at 1 Ag^(-1))and good rate capability(82.1%of capacitance retention at 1–80 Ag^(-1))in 6.0 M KOH electrolyte,together with high energy density(23.3 Wh kg^(-1)at 450 W kg^(-1))in 1.0 M Na_(2)SO_(4)electrolyte.Such excellent performance of SPHA-ac-700–2 is believed to have originated from the crushed sponge-like structure,O/N-co-doping(10.6 at.%O and3.3 at.%N),high SSA,large total pore volume,and hierarchical pore structure.

In-situ self-templating synthesis of 3D hierarchical porous carbonsfrom oxygen-bridged porous organic polymers for highperformance supercapacitors

It is a big challenge to well control the porous structure of carbon materials for supercapacitor application.Herein,a simple in-situ self-templating strategy is developed to prepare three-dimensional(3D)hierarchical porous carbons with good combination of micro and meso-porous architecture derived from a new oxygen-bridged porous organic polymer(OPOP).The OPOP is produced by the condensation polymerization of cyanuric chloride and hydroquinone in NaOH ethanol solution and NaCl is in-situ formed as by-product that will serve as template to construct an interconnected 3D hierarchical porous architecture upon carbonization.The large interface pore architecture,and rich doping of N and O heteroatoms effectively promote the electrolyte accessibility and electronic conductivity,and provide abundant active sites for energy storage.Consequently,the supercapacitors based on the optimized OPOP-800 sample display an energy density of 8.44 and 27.28 Wh·kg^(−1)in 6.0 M KOH and 1.0 M Na2SO4 electrolytes,respectively.The capacitance retention is more than 94%after 10,000 cycles.Furthermore,density functional theory(DFT)calculations have been employed to unveil the charge storage mechanism in the OPOP-800.The results presented in this job are inspiring in finely tuning the porous structure to optimize the supercapacitive performance of carbon materials.

Metal-coordinated porous polydopamine nanospheres derived Fe_(3)N-FeCo encapsulated N-doped carbon as a highly efficient electrocatalyst for oxygen reduction reaction

The exploration of high-efficiency,long-durability,and cost-effectiveness transition metal doped carbon materials to replace the commercial Pt/C in oxygen reduction reaction(ORR)is greatly desirable for promoting the advancement of sustainable energy devices.Herein,the Fe_(3)N and FeCo alloy decorated N-doped carbon hybrid material(denoted Fe_(3)N-FeCo@NC)is prepared and applied as the ORR catalyst,which is derived from the two-step pyrolysis of an intriguing complex consisted of metal-coordinated porous polydopamine(PDA)nanospheres(i.e.,Fe-PDA@Co)and melamine.The resulting Fe_(3)N-FeCo@NC delivers outstanding ORR activity with an onset potential(E_(on))of 1.05 V,a half-wave potential(E_(1/2))of 0.89 V,as well as excellent long-term stability and methanol resistance over Pt/C.Interestingly,the home-made Zn-air battery with Fe_(3)N-FeCo@NC as the air-cathode demonstrates much higher open-circuit voltage(1.50 vs.1.48 V),power density(141 vs.113 mW·cm^(−2))and specific capacity(806.6 vs.660.6 mAh·g^(−1)_(Zn))than those of Pt/C counterpart.Such a remarkable ORR activity of Fe_(3)N-FeCo@NC may stem from the synergistic effect of Fe_(3)N and FeCo active species,the large surface area,the hierarchical porous structure and the exceptional sphere/sheet hybridized architecture.