Binary and Ternary Doping of Nitrogen, Boron, and Phosphorus into Carbon for Enhancing Electrochemical Oxygen Reduction Activity

Choi, Chang Hyuck,Park, Sung Hyeon,Woo, Seong Ihl American Chemical Society 2012 ACS NANO Vol.6 No.8

<P>N-doped carbon, a promising alternative to Pt catalyst for oxygen reduction reactions (ORRs) in acidic media, is modified in order to increase its catalytic activity through the additional doping of B and P at the carbon growth step. This additional doping alters the electrical, physical, and morphological properties of the carbon. The B-doping reinforces the sp<SUP>2</SUP>-structure of graphite and increases the portion of pyridinic-N sites in the carbon lattice, whereas P-doping enhances the charge delocalization of the carbon atoms and produces carbon structures with many edge sites. These electrical and physical alternations of the N-doped carbon are more favorable for the reduction of the oxygen on the carbon surface. Compared with N-doped carbon, B,N-doped or P,N-doped carbon shows 1.2 or 2.1 times higher ORR activity at 0.6 V (<I>vs</I> RHE) in acidic media. The most active catalyst in the reaction is the ternary-doped carbon (B,P,N-doped carbon), which records −6.0 mA/mg of mass activity at 0.6 V (<I>vs</I> RHE), and it is 2.3 times higher than that of the N-doped carbon. These results imply that the binary or ternary doping of B and P with N into carbon induces remarkable performance enhancements, and the charge delocalization of the carbon atoms or number of edge sites of the carbon is a significant factor in deciding the oxygen reduction activity in carbon-based catalysts.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-8/nn3021234/production/images/medium/nn-2012-021234_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn3021234'>ACS Electronic Supporting Info</A></P>

Fe nanoparticles encapsulated in doped graphitic shells as high-performance and stable catalysts for oxygen reduction reaction in an acid medium

Park, Hyun-Suk,Han, Sang-Beom,Kwak, Da-Hee,Han, Jae-Hee,Park, Kyung-Won Elsevier 2019 Journal of catalysis Vol.370 No.-

<P><B>Abstract</B></P> <P>Doped carbon nanostructures with transition metals and nitrogen (N) as doping sources used as promising non-precious metal (NPM) catalysts for oxygen reduction reaction (ORR) have been intensively researched. However, the NPM catalysts, prepared using a mixture of transition metal, nitrogen, and carbon sources, contained both the transition metal-N and N-doped carbon-coated transition metal nanoparticles (NPs) in the surface structure. However, among the transition metal-N and N-doped carbon-coated transition metal NPs, the predominant electrocatalytic active sites for ORR in the NPM catalysts remain uncertain. In this study, we proposed the NPM catalysts for ORR with various active sites such as the doped carbon-coated Fe NPs and/or N- and/or S-doped carbon structures through one- or two-step heating processes. The sample synthesized using a two-step heating process with doped carbon supported Fe NPs and dicyandiamide exhibited significantly improved activity and stability for ORR in O<SUB>2</SUB>-saturated H<SUB>2</SUB>SO<SUB>4</SUB>, due to a synergistic effect by the co-doping of S and N in the carbon structure and the Fe NPs encapsulated in the doped carbon, comparable to a commercial Pt/C catalyst. In particular, the Fe NPs encapsulated in the N- and S-doped carbon layers with a nanometer scale thickness are found to be an electrocatalytic active site for ORR.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NPM cathode catalysts for ORR were prepared through one- or two-step heating processes. </LI> <LI> The sample synthesized using a two-step heating process exhibited improved ORR performance. </LI> <LI> The improved performance is attributed to the co-doping and the Fe NPs in the doped carbon. </LI> <LI> The Fe NPs in the carbon layers might be considered as an electrocatalytic active site for ORR. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synergistic effect of heteroatom-doped activated carbon for ultrafast charge storage kinetics

Shin, Dong-Yo,Sung, Ki-Wook,Ahn, Hyo-Jin Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.478 No.-

<P><B>Abstract</B></P> <P>Providing a crystallographic and electronic modification of carbon-based materials in electrical double-layer capacitors (EDLCs) is an essential technology needed to improve the charge storage kinetics and to enhance ultrafast cycling performances. However, despite numerous structural composite and morphological modification efforts focused on active materials, ultrafast charge storage kinetics still indicated a poor ultrafast capacitance and low cycling stability. To solve these problems, in the present study, we propose a novel heteroatom (N, P, and B)-doped activated carbon (AC) that has the synergistic effects of N-, P-, and B-doping using the one-pot doping calcination process. Compared to the bare-AC, N-doped AC, P-doped AC, and B-doped AC, the novel heteroatom-doped AC indicates an improved ultrafast charge storage kinetics, such as high specific capacitance (243.9 F g<SUP>−1</SUP> at the scan rate of 10 mV s<SUP>−1</SUP>), good cycling stability (216.7 F g<SUP>−1</SUP> at 100 mV s<SUP>−1</SUP> after 500 cycles), and superb ultrafast cycling capacitance (199.7 F g<SUP>−1</SUP> at 300 mV s<SUP>−1</SUP>). These superb electrochemical performances can be attributed by synergistic effects of increased active sites by N-doping related to a high charge storage area, improved functional groups by P-doping related to an excellent wettability between the electrode and the electrolyte, and enhanced electrical properties by B-doping related to a good electron acceptability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The heteroatom (nitrogen, phosphate, and boron)-doped activated carbon. </LI> <LI> The heteroatom-doped activated carbon showed increase of active site by N doping. </LI> <LI> The heteroatom-doped activated carbon exhibited improvement of functional groups by P doping. </LI> <LI> The heteroatom-doped activated carbon indicated enhancement of electron acceptability by B doping. </LI> </UL> </P>

Facile and scalable synthesis of nitrogen-doped ordered mesoporous carbon for high performance supercapacitors

Lei Fan,Peizheng Sun,Li Yang,Zhilong Xu,Jie Han 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.1

Nitrogen-doped carbon has been receiving tremendous research interest due to its exotic electrochemical performance and catalyzing capability. Nevertheless, large-scale synthesis of ordered, mesoporous, nitrogen-doped carbon for supercapacitors is rarely reported due to the complexity and uncontrollable property of polymerization of carbon/ nitrogen precursors. In this work, we report a facile and efficient approach for mass production of nitrogen-doped carbon, with a narrow pore size distribution and a sheet morphology, via a simple solution casting of biomass-based mixture. Upon drying, the gelatin molecules self-assemble into sheets, and guide the homogeneous loading of sacrificial silica nanospheres. Further carbonization and template removal procedures allow the low-cost production of nitrogendoped carbon sheets in the absence of complex polymerization. As a result, nitrogen-doped carbon sheets possess a high nitrogen content and ordered, interconnected mesoporous channels, with porosity parameters being carbonization temperature and template size dependence. Additionally, nitrogen-doped, ordered carbon sheets exhibit high performance for supercapacitor application, including high specific capacitances and energy/power densities. This work demonstrates a unique route to synthesizing ordered mesoporous nitrogen-doped carbon sheets via a scalable, low-cost method, which may shed light on many other applications aside from energy storage, such as water splitting, catalysis and sensor.

Nitrogen-doped nanoporous carbons derived from lignin for high CO2 capacity

박소현,최민성,박호석 한국탄소학회 2019 Carbon Letters Vol.29 No.3

In this paper, nitrogen (N)-doped ultra-porous carbon derived from lignin is synthesized through hydrothermal carbonization, KOH activation, and post-doping process for CO2 adsorption. The specific surface areas of obtained N-doped porous carbons range from 247 to 3064 m2/g due to a successful KOH activation. N-containing groups of 0.62–1.17 wt% including pyridinic N, pyridone N, pyridine-N-oxide are found on the surface of porous carbon. N-doped porous carbon achieves the maximum CO2 adsorption capacity of 13.6 mmol/g at 25 °C up to 10 atm and high stability over 10 adsorption/desorption cycles. As confirmed by enthalpy calculation with the Clausius–Clapeyron equation, an adsorption heat of N-doped porous carbon is higher than non-doped porous carbon, indicating a role of N functionalities for enhanced CO2 adsorption capability. The overall results suggest that this carbon has high CO2 capture capacity and can be easily regenerated and reused without any clear loss of CO2 adsorption capacity.

Monodispersed N-Doped Carbon Nanospheres for Supercapacitor Application

Lee, Whon-hee,Moon, Jun Hyuk American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.16

<P>Highly monodispersed nitrogen-doped carbon nanospheres are prepared by the pyrolytic carbonization of emulsion-polymerized polystyrene-based colloidal spheres in the presence of a nitrogen-enriched molecule, melamine (1,3,5-triazine-2,4,6-triamine). The nitrogen-doped carbon spheres are successfully tested for use as electrode materials in supercapacitors. The nitrogen content incorporated into the carbon sphere is controlled by changing the weight ratio of melamine to the polymer spheres. The nitrogen doping concentration is proportional to the mixing weight ratio. The nitrogen doping produces relatively abundant pyridinic and pyrrolic configurations, and these configurations are observed to be more abundant for carbon spheres with high nitrogen doping. The nitrogen doping enhances the pseudocapacitance and the electrical conductivity of carbon, thereby enhancing the specific capacitance. We obtain a specific capacitance of up to 191.9 F g<SUP>–1</SUP> with 20% nitrogen doped carbon nanospheres, which is 14 times higher than that of the undoped carbon nanospheres. Moreover, the capacitance retention remains up to 10 000 cycles, which clearly displays a good cycling stability the nitrogen-doped carbon nanospheres as the supercapacitve electrode materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-16/am5033378/production/images/medium/am-2014-033378_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5033378'>ACS Electronic Supporting Info</A></P>

Study of the structure-properties relations of carbon spheres affecting electrochemical performances of EDLCs

Kim, Hee Soo,Abbas, Muhammad Awais,Kang, Min Seok,Kyung, Hyuna,Bang, Jin Ho,Yoo, Won Cheol Elsevier 2019 ELECTROCHIMICA ACTA Vol.304 No.-

<P><B>Abstract</B></P> <P>For high performance of electrical double layer capacitors (EDLCs), a high specific surface area (SSA) and N-doping level, and small particle size of carbonaceous materials, have been believed to be crucial factors. However, there have been few reports on simultaneous study of the structure-properties relations of carbons and the electrochemical performances of EDLCs. Herein, we report the relationship between the structural properties of carbons, such as the SSA, N-doping, and particle size, and the electrochemical properties of EDLCs by using a series of well-defined carbons. Monodisperse and size-tunable resorcinol-formaldehyde carbon (RFC) spheres were synthesized and activated by hot CO<SUB>2</SUB> treatment to increase the SSA up to 3958 m<SUP>2</SUP>/g (RFC_C390 sample). When the specific capacitances of the RFC spheres were plotted in terms of their SSAs, an almost perfect correlation (R<SUP>2</SUP> = 0.99) was observed, which confirmed the linear relationship between the specific capacitance and the SSA. In addition, N-doped melanin C (MC) spheres were synthesized and subsequently activated for N-doping effect. Activated MC (MC_C130), which exhibited similar SSA (2618 m<SUP>2</SUP>/g) and size (301 nm) but a different N-doping level (3.1%) compared with those (2793 m<SUP>2</SUP>/g, 312 nm, and 1.3%, respectively) of the activated RFC spheres (RFC_C120), displayed higher specific capacitance (288 F/g), capacitance retention (64%), and long term stability over 5000 cycles (93%) compared with those (260 F/g, 58%, and 90%, respectively) of the RFC counterparts. To observe the particle size effect, different sizes (98, 280, and 579 nm) of RFC spheres with similar SSAs (3981, 3958, and 3898 m<SUP>2</SUP>/g, respectively) and pore size distributions were prepared, such that the smallest RFC revealed the best EDLC performance in terms of specific capacitance (360 F/g), capacitance retention (70%), and long term stability over 5000 cycles (98%), all of which could be compared with the values reported in the literature. Furthermore, all of the Carbon samples were analyzed by using electrochemical impedance spectroscopy for confirming the structure-properties relations of carbon spheres with the electrochemical performances of EDLCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Monodisperse and size-tunable carbon spheres were synthesized and activated by hot CO<SUB>2</SUB> treatment. </LI> <LI> Structure-properties relations of carbon spheres with electrochemical performance of EDLCs were elucidated. </LI> <LI> EIS study also supported the relationship of structure-properties of carbon and EDLC performances. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nitrogen‑doped nanoporous carbons derived from lignin for high CO2 capacity

Sohyun Park,Min Sung Choi,Ho Seok Park 한국탄소학회 2019 Carbon Letters Vol.29 No.3

In this paper, nitrogen (N)-doped ultra-porous carbon derived from lignin is synthesized through hydrothermal carbonization, KOH activation, and post-doping process for CO2 adsorption. The specific surface areas of obtained N-doped porous carbons range from 247 to 3064 m2/g due to a successful KOH activation. N-containing groups of 0.62–1.17 wt% including pyridinic N, pyridone N, pyridine-N-oxide are found on the surface of porous carbon. N-doped porous carbon achieves the maximum CO2 adsorption capacity of 13.6 mmol/g at 25 °C up to 10 atm and high stability over 10 adsorption/desorption cycles. As confirmed by enthalpy calculation with the Clausius–Clapeyron equation, an adsorption heat of N-doped porous carbon is higher than non-doped porous carbon, indicating a role of N functionalities for enhanced CO2 adsorption capability. The overall results suggest that this carbon has high CO2 capture capacity and can be easily regenerated and reused without any clear loss of CO2 adsorption capacity.

Nitrogen and sulfur dual-doped porous carbon derived from coffee waste and cysteine for electrochemical energy storage

홍주미,김하림,이지은,고유나,박기태,김영은,윤민혜,정순관,박진원,이원희 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.7

N/S dual-doped carbon materials were synthesized from coffee waste and cysteine for use as porous carbon electrode materials for electric double layer capacitors. The capacitance of the carbon materials was calculated from the experimental results of cyclic voltammetry and galvanostatic charge-discharge tests. The N/S-doped carbon materials obtained from heat-treatment with cysteine exhibited a higher discharge capacitance, 71.3 F/g, than that of the carbon without the cysteine treatment, 43.8 F/g, at 1 A/g. This is because the N/S dual-doped carbons possess a higher wettability than that of the other carbon material, even though the N/S doping with cysteine destroys the porous carbon structure, which reduces the BET surface area of the carbon samples. Elemental analysis was performed to determine the portions of nitrogen and sulfur elements doped into the carbon. From the XPS results, various states of nitrogen and sulfur elements were identified, and SEM/TEM images were obtained to observe their morphologies and porous structures.

Superior pore network retention of carbon derived from naturally dried ginkgo leaves and its enhanced oxygen reduction performance

Razmjooei, F.,Singh, K.P.,Yu, J.S. Elsevier Science Publishers 2016 CATALYSIS TODAY - Vol.260 No.-

<P>Obtaining a highly porous carbon has always been considered as an essential issue in many electrochemical applications. Ginkgo leaves have not only unique shape and color, but also interesting chemical and medical properties, which have inspired us to investigate them. In present approach, the naturally dried yellow ginkgo leaves, collected in autumn season, are directly used to prepare the porous carbon with simple two-step template-free procedure of pyrolysis at different temperatures followed by acid treatment for removal of inherent mineral salts. Interestingly, it is found that inherent salts present in the resulting carbon backbone can play as porogen to create high amount of pores in the carbon framework when the salts are removed by acid treatment. Effect of alternations in ginkgo leaves structure during the climate change, from spring to autumn, on ORR activity is examined for the first time on the carbons obtained by carbonizing different color, greenish and yellowish, ginkgo leaves at 1000 degrees C. Yellow leaves can maintain their original tissue structure during the gradual drying in cold weather of late fall, which results in formation of more stable structure, leading to development of much more pores and larger surface area in the resulting carbon. The unforeseen results exhibit surprisingly higher ORR activity for carbon catalyst obtained from yellow leaves (LY-1000) compared with one prepared from green leaves collected in summer, (LG-1000). Higher surface area of LY-1000 is found to be the most important key factor for its enhanced ORR activity. Furthermore, electrocatalytic property of the carbon greatly depends on the carbonization temperature, which is a crucial factor to make a balance between electrical conductivity, heteroatom doping and surface area. As the temperature increases, the heteroatom doping decreases, which is not favorable for ORR, but at the same time, the conductivity and surface area increase, which is beneficial for ORR, indicating intriguing trade-off between them as a function of temperature, which needs to be optimized for best ORR performance. Moreover, present work enables a large-scale production of efficient heteroatom-doped porous carbon from ginkgo leaf waste without using any activation and templating agents. (C) 2015 Elsevier B.V. All rights reserved.</P>