In this study, N/S co-doped carbon felt (N/S-CF) was prepared and characterized as an electrode material for electric double-layer capacitors (EDLCs). A commercial carbon felt (CF) was immersed in an aqueous solution of thiourea and then thermally treated at 800 oC under an inert atmosphere. The prepared N/S-CF showed a large specific surface area with hierarchical pore structures. The electrochemical performance of the N/S-CF-based electrode was evaluated using both 3- electrode and 2-electrode systems. In the 3-electrode system, the N/S-CF-based electrode showed a good specific capacitance of 177 F/g at 1 A/g and a good rate capability of 41% at 20 A/g. In the 2-electrode system (symmetric capacitor), the freestanding N/S-CF-based electrode showed a specific capacitance of 275 mF/cm2 at 2 mA/cm2, a rate capability of 62.5 % at 100 mA/cm2, a specific power density of ~ 25,000 mW/cm2 at an energy density of 23.9 mWh/cm2, and a cycling stability of ~ 100 % at 100 mA/cm2 after 20,000 cycles. These results indicate the N/S co-doped carbon felts can be a promising candidate as a new electrode material in a symmetric capacitor.

Hierarchically porous carbon materials with high nitrogen functionalities are extensively studied as highperformance supercapacitor electrode materials. In this study, nitrogen-doped porous carbon textile (N-PCT) with hierarchical pore structures is prepared as an electrode material for supercapacitors from a waste cotton T-shirt (WCT). Porous carbon textile (PCT) is first prepared from WCT by two-step heat treatment of stabilization and carbonization. The PCT is then nitrogendoped with urea at various concentrations. The obtained N-PCT is found to have multi-modal pore structures with a high specific surface area of 1,299 m2 g−1 and large total pore volume of 1.01 cm3 g−1. The N-PCT-based electrode shows excellent electrochemical performance in a 3-electrode system, such as a specific capacitance of 235 F g−1 at 1 A g−1, excellent cycling stability of 100 % at 5 A g−1 after 1,000 cycles, and a power density of 2,500 W kg−1 at an energy density of 3.593 Wh kg−1. Thus, the prepared N-PCT can be used as an electrode material for supercapacitors.

Porous carbons have been widely used as electrode material for supercapacitors. However, commercial porous carbons, such as activated carbons, have low electrochemical performance. Nitrogen-doping is one of the most promising strategies to improve electrochemical performance of porous carbons. In this study, nitrogen self-doped porous carbon (NPC) is prepared from melamine foam by carbonization to improve the supercapacitive performance. The prepared NPC is characterized in terms of the chemical structures and elements, morphology, pore structures, and electrochemical performance. The results of the N2 physisorption measurement, X-ray diffraction, and Raman analyses reveal that the prepared NPC has bimodal pore structures and pseudo-graphite structures with nitrogen functionality. The NPC-based electrode exhibits a gravimetric capacitance of 153 F g−1 at 1 A g−1, a rate capability of 73.2 % at 10 A g−1, and an outstanding cycling ability of 97.85% after 10,000 cycles at 10 A g−1. Thus, the NPC prepared in this study can be applied as electrode material for high-performance supercapacitors.

Carbon supports for dispersed platinum (Pt) electrocatalysts in direct methanol fuel cells (DMFCs) are being continuously developed to improve electrochemical performance and catalyst stability. However, carbon supports still require solutions to reduce costs and improve catalyst efficiency. In this study, we prepare well-dispersed Pt electrocatalysts by introducing titanium dioxide (TiO2) into biomass based nitrogen-doped carbon supports. In order to obtain optimized electrochemical performance, different amounts of TiO2 component are controlled by three types (Pt/TNC-2 wt%, Pt/TNC-4 wt%, and Pt/TNC-6 wt%). Especially, the anodic current density of Pt/TNC-4 wt% is 707.0 mA g−1 pt, which is about 1.65 times higher than that of commercial Pt/C (429.1 mA g−1 pt); Pt/TNC-4wt% also exhibits excellent catalytic stability, with a retention rate of 91 %. This novel support provides electrochemical performance improvement including several advantages of improved anodic current density and catalyst stability due to the well-dispersed Pt nanoparticles on the support by the introduction of TiO2 component and nitrogen doping in carbon. Therefore, Pt/TNC-4 wt% may be electrocatalyst a promising catalyst as an anode for high-performance DMFCs.

The design of non-precious electrocatalysts with low-cost, good stability, and an improved oxygen reduction reaction(ORR) to replace the platinium-based electrocatalyst is significant for application of fuel cells and metal-air batteries with high energy density. In this study, we synthesize iron-carbide(Fe3C) embedded nitrogen(N) doped carbon nanofiber(CNF) as electrocatalysts for ORRs using electrospinning, precursor deposition, and carbonization. To optimize electrochemical performance, we study the three stages according to different amounts of iron precursor. Among them, Fe3C-embedded N doped CNF-1 exhibits the most improved electrochemical performance with a high onset potential of −0.18 V, a high E1/2 of −0.29 V, and a nearly four-electron pathway (n = 3.77). In addition, Fe3C-embedded N doped CNF-1 displays exellent long-term stabillity with the lowest ΔE1/2= 8 mV compared to the other electrocatalysts. The improved electrochemical properties are attributed to synergestic effect of N-doping and well-dispersed iron carbide embedded in CNF. Consequently, Fe3C-embedded N doped CNF is a promising candidate for non-precious electrocatalysts for high-performance ORRs.

Nitrogen (N)-doped protein-based carbon as platinum (Pt) catalyst supports from tofu for oxygen reduction reactions are synthesized using a carbonization and reduction method. We successfully prepare 5 wt% Pt@N-doped protein-based carbon, 10 wt% Pt@N-doped protein-based carbon, and 20 wt% Pt@N-doped protein-based carbon. The morphology and structure of the samples are characterized by field emission scanning electron microscopy and transmission electron micro scopy, and crystllinities and chemical bonding are identified using X-ray diffraction and X-ray photoelectron spectroscopy. The oxygen reduction reaction are measured using a linear sweep voltammogram and cyclic voltammetry. Among the samples, 10 wt% Pt@N-doped protein-based carbon exhibits exellent electrochemical performance with a high onset potential of 0.62 V, a high E1/2 of 0.55 V, and a low ΔE1/2= 0.32 mV. Specifically, as compared to the commercial Pt/C, the 10 wt% Pt@N-doped proteinbased carbon had a similar oxygen reduction reaction perfomance and improved electrochemical stability.

N-doped carbon nanofibers as catalysts for oxygen-reduction reactions are synthesized using electrospinning and carbonization. Their morphologies, structures, chemical bonding states, and electrochemical performance are characterized. The optimized N-doped carbon nanofibers exhibit graphitization of carbon nanofibers and an increased nitrogen doping as well as a uniform network structure. In particular, the optimized N-doped carbon nanofibers show outstanding catalytic activity for oxygen-reduction reactions, such as a half-wave potential (E1/2) of 0.43 V, kinetic limiting current density of 6.2 mA cm-2, electron reduction pathways (n = 3.1), and excellent long-term stability after 2000 cycles, resulting in a lower E1/2 potential degradation of 13 mV. The improvement in the electrochemical performance results from the synergistic effect of the graphitization of carbon nanofibers and the increased amount of nitrogen doping.

Tantalum nitrides () have been developed to substitute the Cd based pigments for non-toxic red pigment. Various doping elements were doped to reduce the amount of high price Tantalum element used and preserve the red color tonality. Doping elements were added in the synthesizing process of precursor of amorphous tantalum oxides and then Tantalum nitrides doped with various elements were obtained by ammonolysis process. The average particle size of final nitrides with secondary phases was larger than the nitride without the secondary phases. Also secondary phases reduced the red color tonality of final products. On the other hand, final nitrides without secondary phase had orthorhombic crystal system and presented good red color. In other words, in the case of nitrides without secondary phases, doping elements made a solid solution of tantalum nitride. In this context, doping process controlled the ionic state of nitrides and the amount of oxygen/nitrogen in final nitrides affected the color tonality.