Highly nitrogen and sulfur dual-doped carbon microspheres for supercapacitors

Heteroatom doping, especially dual-doped carbon materials have attracted much attention for the past few years, and have been regarded as one of the most efficient strategies to enhance the capacitance behavior of porous carbon materials. In this work, a facile two-step synthetic route was developed to fab- ricate nitrogen and sulfur co-doped carbon microsphere （NSCM） by using thiourea as dopant. The NJS doping content is controlled via varying the carbonization temperature. It has been proved that a suitable quantity of N and S groups could not only provide pseudo-capacitance but also promote the electron transfer for carbon materials, which ensures the further utilization of the exposed surfaces for charge storage. The optimized NSCM prepared at a carbonization temperature of 800 ℃ （NSCM-800） achieves a capacitance of 277.1 F g^-1 at a current density of 0.3 A g^-1 in 6.0 mol L^-1 KOH electrolyte, which is 71% higher than that of undoped carbon microsphere. Besides, NSCM-800 shows an excellent cycling stability, 98.2% of the initial capacitance is retained after 5,000 cvcles at a current densitv of 3.0 A g^-1.

Ultrafine molybdenum carbide nanoparticles supported on nitrogen doped carbon nanosheets for hydrogen evolution reaction

Molybdenum carbides(Mo_xC)/nitrogen doped carbon nanosheets(NCS) composites are synthesized via simple mixing melamine and ammonia molybdate, followed by a high-temperature treatment. Metal carbide nanoparticles with ultra-small size(13nm) are uniformly supported on nitrogen doped carbon nanosheets. The hydrogen evolution reaction(HER) is investigated in both 0.5 mol/L H_2SO_4 and 1 mol/L KOH media. Mo_2C/NCS-10(melamine/ammonia molybdate weight ratio of 10:1) exhibits excellent performance with a low overpotential of 130 mV in 0.5 mol/L H_2SO_4 solution and 108 mVin 1mol/L KOH solution at the current density of 10 mA/cm^2. The better electrocatalytic activity could be ascribed to Ndoped carbon nanosheets, small particle size, mesoporous structure, and large specific surface area,which could provide the large electrochemical active surface area and facilitate mass transport.

Biomass derived nitrogen doped carbon with porous architecture as efficient electrode materials for supercapacitors

Developing porous carbon materials with low-cost, sustainable and eco-friendly natural resources is emerging as an ever important research field in the application of high-performance supercapacitor. In this paper, a simple synthetic method to fabricate nitrogen doped porous carbon （NPC） is developed via a one-pot carbonization of sodium alginate and urea. The as-prepared NPC annealed at 700℃ with meso- and macro-porous structure exhibits excellent specific capacitance （180.2 F/g at 1 A/g） and superior cycling life when serves as electrode materials for supercapacitor. Moreover, the investigation on the annealing temperature demonstrates that NPC pyrolysis at 700℃ possesses relatively high pyrrole nitrogen and pyridine nitrogen, which is favorable for enhancing supercapacitor performance. This work extends biomass derived carbon materials in energy storage applications.