Heteroatom-doped Carbon Materials Research Articles

Enhanced specific capacity and cycle stability of hybrid supercapacitors using carbonized polyphosphazene-based nanocomposites

This work aims to explore the utility of the polyphosphazene-based nanomaterials as both negative and positive heteroatom-doped porous carbon materials in hybrid supercapacitors. To this end, carbonized Poly (hexachlorocyclotriphosphazene-co-bisphenol S) (PZS) microspheres at different temperatures were employed as negative materials and carbonized Ag nanowires/PZS nanocomposites (Ag NWs @ PZSC) were used as positive materials. The carbonized PZS microspheres at 900 oC (PZSC900) exhibited a lager surface area with more micropores than PZSC700 and PZSC800, endowing the former with a distinguished specific capacitance (193.2 F g−1) and an outstanding cycle stability (nearly 100% after 10000 cycles). The Ag NWs @ PZSC with an amorphous carbon coating layer outperforms the Ag NWs, reaching a specific capacity of 113.33 mAh g−1. Importantly, the optimized negative and positive materials were rationally assembled to an asymmetric cell in an alkaline aqueous electrolyte, which exhibited a cell specific capacitance of 76.6 F g−1 and a cycle stability of 92.11% after 10000 cycles. The findings demonstrate that PZS is a promising precursor for constructing high-performance hybrid supercapacitors.

N-O-P co-doped porous carbon aerogel derived from low-cost biomass as electrode material for high-performance supercapacitors

Heteroatom-doped porous carbon materials have attracted great interest and are considered promising candidate electrode materials for supercapacitors. Here, a facile and effective strategy is developed for the synthesis of porous carbon aerogels from abundant renewable radishes. Based on the high oxygen content of biomass, N-O-P co-doped of the carbon aerogel was achieved by introducing NH4H2PO4 during ZnCl2 activation process. A continuous three-dimensional porous network interconnected was obtained with uniform distribution of O, N and P on the whole aerogel framework. The N-O-P co-doped functional groups improve the conductivity and wettability of the material and stimulate the additional Faraday reaction, and thus can impart a variety of beneficial effects to the electrochemical performance of the material. The N-O-P co-doped carbon aerogel exhibits a high gravimetric specific capacitance of 352 F/g at a current density of 1 A/g in the three-electrode system using 6 M KOH as the electrolyte. Besides, the material also exhibits a high specific capacitance retention rate of 78.4% by increasing the current density from 1 to 10 A/g. In 10,000 cycles of charging and discharging performance, the N-O-P co-doped aerogel exhibits excellent cycle stability with only a slight capacitance loss of less than 10%.

Facile synthesis of nitrogen, phosphorus and sulfur tri-doped carbon nanosheets as efficient oxygen electrocatalyst for rechargeable Zn-air batteries

The rechargeable Zn-air battery plays vital roles in renewable energy storage and conversion, but the scarcity of highly efficient air cathode electrocatalysts severely hampers its commercial popularizing. Heteroatoms-doped carbon materials have attracted many interests, because the resulted dopants synergistic effect always brings about extraordinary electrocatalytic activities. Herein, a simple pyrolysis strategy of thiourea, phytic acid and graphene oxide was developed to prepare N, P and S tri-doped carbon nanosheets, featuring sheet structure with specific surface area of 479 m2 g−1 and sufficient dopants (3.78 at% N, 7.97 at% P, and 1.36 at% S). Benefiting from the dominated graphitic and pyridinic N moieties, as well as abundant P-C and S-C functional groups, all of which are desired active species for oxygen electrochemistry, the synthesized tri-doped carbon nanosheets exhibit superior oxygen reduction performance and enhanced oxygen evolution activity in alkaline electrolyte. As the air cathode electrocatalysts for rechargeable Zn-air batteries, the decreased charge–discharge potential gaps and robust cycling stability are observed, even superior to those of noble-metal Pt/C benchmarks. The interconnected porous architecture with high surface area, multiple active species, and significant electric conductivity capability are considered as main factors for the enhanced electrochemical activities of this tri-doped carbon material.

Importance of Doping Sequence in Multiple Heteroatom-Doped Reduced Graphene Oxide as Efficient Oxygen Reduction Reaction Electrocatalysts

Multiple heteroatom-doped graphene is of great interest for developing an efficient electrocatalyst for oxygen reduction reaction (ORR). To maximize the electrocatalytic performance of doped graphene, the competitive doping mechanism caused by the different atomic sizes of dopants should be developed. Herein, three different heteroatoms (e.g., N, P and B) are competitively introduced into reduced graphene oxide (RGO) using both single- and two-step processes. The total quantity of heteroatoms for ternary RGO synthesized using the two-step process is lower than that when using the single-step process. Higher ORR electrocatalytic activity for the two-step-synthesized RGO compared to the single-step-synthesized RGO can be explained by: (a) a high amount of P atoms; (b) the fact that B doping itself decreases the less electrocatalytic N moieties such as pyrrole and pyridine and increases the high electrocatalytic moieties such as quaternary N; (c) a high amount of B atoms itself within the RGO act as an electrocatalytic active center for O2 adsorption; and (d) a small amount of substitutional B might increase the electrical conductivity of RGO. Our findings provide new insights into the design of heteroatom-doped carbon materials with excellent electrocatalytic performance.

Multifunctional N and O co-doped 3D carbon aerogel as a monolithic electrode for either enzyme immobilization, oxygen reduction and showing supercapacitance

Herein, a novel N and O co-doped three dimensional (3D) hybrid carbon aerogel (CA) was prepared by a two-step carbonization technology, i.e. preoxidation process (240 °C, air atmosphere) and carbonization process (600∼1000 °C, nitrogen atmosphere). It was found that the peroxidation process could improve the thermostability and heteroatoms content during the carbonization. The obtained CA samples inherited their original morphology of “string-bead” network and had a higher heteroatoms content, while the control samples did not. We focused on the application of this CA in either lactate oxidase-modified, super-capacitive and oxygen reductive electrodes. The fabricated lactate-powered integrated electronic skin could produce a maximum power density of ca. 1.3 mW cm−2, which allowed powering a multiplexed metabolic electronic in situ. The sample of CF-PVA-PANI800 showed the highest specific capacitance of 427.2 F g−1 at a discharge specific current of 0.5 A g−1. The synergistic effect of the N functionalities endowed the sample of CF-PVA-PANI900 with similar electrocatalytic activity to a 20 wt% commercial Pt/C catalyst for ORR. This fabrication strategy of carbon aerogel may provide a new alternative for preparing more heteroatom-doped 3D carbon materials in future.

Synthesis of Nitrogen-Doped Hierarchical Porous Carbon Materials and its Catalytic Ability in Hydrogen Evolution Reaction

Hydrolysis for hydrogen production is one of the most efficient ways to produce hydrogen energy. In order to realize its wide application, people urgently need to find cheap and efficient metal-free electrocatalysts to replace the noble-metal electrocatalysts in hydrogen evolution reaction (HER). Here, N-doped hierarchical porous carbon materials were successfully fabricated without any template. We changed the nitrogen and carbon source needed to prepare the material and tested HER performance. In all samples, the ethylenediamine-based porous carbon material (NPC-2) compared with other nonmetallic heteroatom doped carbon materials and some traditional metallic catalysts exhibited outstanding HER performance and stability in acid solution. To achieve a 10 mA/cm2 HER current density, the nitrogen-doped hierarchical porous carbon materials (NPC-2) required an overpotential of 398 mV.

Modifying carbon nanotubes supported palladium nanoparticles via regulating the electronic metal–carbon interaction for phenol hydrogenation

Heteroatom doped carbon materials have been synthesized and served as catalyst supports for Pd nanoparticles (NPs). Numerous Pd-carbon catalysts can be produced via single-, dual-, and multi-doping heteroatoms into carbon supports. Therefore, it is highly desired to seek a universal descriptor, regardless of the doping types, in guiding to the design of efficient catalysts. The electronic state of Pd affected by carbon supports is crucial in catalysis, which can be described by the binding energy (BE) accurately and conveniently using X-ray photon spectroscopy. In this work, the single (dual)-doped carbon nanotubes (CNTs) with tunable doping degrees were synthesized via thermal pyrolysis of heteroatom-containing precursors, accompanied by the defluorination of fluorinated CNTs. Density functional theory results show that the charge distributions of the doped-CNTs are determined by the doping configurations. After loading Pd NPs, the charge of the support redistributes. Meanwhile, the BEs of Pd0 3d5/2 change correspondingly due to the electronic metal–carbon interaction (EMCI). Eventually, Pd NPs with different electronic states show the difference in the turnover frequency of phenol hydrogenation. Therefore, the electronic state of Pd NPs can be considered as a proper descriptor for estimating the catalytic performance and indicator for developing highly efficient catalysts.

Benzene hydrogenation activities of Ni catalyst supported on N- and B-doped carbons

A catalyst support can improve the catalytic activity of metal catalysts, and this phenomenon is well known as the support effect. The effective use of this support effect is considered important for improving catalytic activity. However, the factors affecting this phenomenon are complex. It is, therefore, important to understand the interaction between the support and metal catalyst as well as the surface characteristics of the support for elucidating this phenomenon. Carbon is a useful support material because of its high chemical and thermal stability and electroconductivity. Moreover, its surface properties can be controlled by doping the carbon structure with heteroatoms. In this study, the catalytic activity of metal particles supported on heteroatom-doped carbon materials was evaluated to investigate the support effect of the doped carbon. The catalytic activity of carbon-supported Ni particles in benzene hydrogenation was improved by introducing N and B into the carbon support. In particular, Ni supported on N-doped carbon showed a two-fold improvement in activity compared to that supported on undoped carbon. A compensation effect was confirmed for the catalytic activity of Ni particles. The results suggest that the introduction of heteroatoms into the carbon support changed the adsorption energy of the reactant on Ni, thereby improving the Ni catalytic activity.

Insights into oxygen reduction reaction on pristine carbon nanoparticles synthesized by the plasma-in-liquid process

Carbon-based materials have been widely studied as promising energy conversion materials that can replace noble metal catalysts. In addition, the plasma-in-liquid process has recently been used to synthesize heteroatom-doped carbon materials for oxygen reduction reactions, such as nitrogen-, boron-, and halogen-doped carbon. However, there has been a lack of insight into pristine carbon, which is the base material for such reactions. In this study, pristine carbon materials (Cx-P) were synthesized using a plasma-in-liquid process, and the material properties and oxygen reduction reaction (ORR) performance were analyzed with respect to heat treatment. Cx-P was successfully synthesized as a carbon nanoparticle and redesigned as partially crystallized carbon with various pore-size distributions using heat treatment. The 2-electron-transfer ORR pathway was identified as the intrinsic reduction route. On the other hand, the electrochemical activity increased with heat treatment, showing an unexpectedly superior kinetic current density of ~18.30 mA cm−2 (at 0.5 V vs. RHE). Our results are expected to provide an important reference to the ORR performance of the relevant carbon materials, including insights into the basic material properties of partially crystallized porous carbon synthesized using the plasma-in-liquid process.

Ionic liquid-derived Fe, N, S, F multiple heteroatom-doped carbon materials for enhanced oxygen reduction reaction

Heteroatoms doped carbon catalysts have been intensively studied to take the place of Platinum based catalysts for oxygen reduction reaction (ORR) because of their ideal catalytic activity. Herein, the microporous–mesoporous carbon material catalysts doped with Fe, N, S and F were synthesized through a plain one-pot pyrolysis method with ionic liquid 1-butyl-3-methyli-midazolium bis((trifluoromethyl)sulfonyl)imide ([Bmim][TF2N]) and melamine as precursors. Electrochemical analysis shows that the ORR activity and stability of the obtained catalysts are obviously better than Pt/C under alkaline condition. Meanwhile, the catalysts show similar ORR activity and much better durability in 0.1 M HClO4 comparing to Pt/C. Moreover, the tolerance of methanol in both basic and acid solutions is greatly better than Pt/C. The high activity is ascribed to the large specific surface area, porous structure and the synergistic effect between S, F, pyridine N, graphite N and Fe–N x . The high stability possibly comes from the appropriate graphitization and the carbon-coating effect. The strategy proposed here has the advantages of facile, low cost, high efficiency and easy large-scale production, which provides new ideas for the preparation of high-performance Fe–N–C electrocatalysts.

Lignosulfonate for improving electrochemical performance of chitin derived carbon materials as a superior anode for lithium-ion batteries

Lignosulfonate, a by-product spent sulfite pulping liquor from the paper and pulping industry, was a suitable natural sulfur dopant for improving electrochemical performance of chitin derived carbon materials. Herein, a cost-effective method of possible large-scale production was reported to fabricate heteroatoms-doped porous carbon (CLs) as advanced electrode materials for lithium-ion batteries applications. After a simple pyrolysis process of chitin mixed with lignosulfonate, generated CLsequipped with abundant defect structures. Remarkably, although portion of lignosulfonate (1/3 of chitin) was introduced, the specific surface area (SSA) of CLs enhanced to 411.64 m2g−1 (CL800). In addition, its capacitive characteristic improved, effectively, delivering high a reversible specific capacity of up to 644.5 mA h g−1 at current density of 50 mA g−1. After 300 cycles at the current density of 100 mA g−1, it still remained a specific capacity of 350.7 mA g−1. Such anode material presented excellent electrochemical performance, good rate capability and cycling stability, attributed to containing abundant N and S elements, providing a green avenue for converting biomass waste to high electrochemical performance heteroatoms-doped carbon materials, having promising application in the energy storage field.

Boosting hydrogen evolution reaction on few-layer graphdiyne by sp-N and B co-doping

Hydrogen evolution reaction (HER) catalysts based on noble metals traditionally suffered from high cost, low activity, and poor stability. Metal-free catalysts originating from heteroatom-doped carbon materials have been proposed to address these problems, in which the doping configurations and electronic structures are critical for modulating the electrocatalytic activity. Herein, we reported a sequential approach for the co-doping of B and N atoms into graphdiyne (GDY). We noticed that the configurations of heteroatoms are strongly related to the doping process, and the subsequent HER test shows that a certain sp-N can decrease the overpotential, and further introduction of B atoms can continuously enhance the current density owing to the synergistic effect of chemical and electronic couplings on proton adsorption/reduction kinetics. This work provides a deeper understanding of developing dual heteroatom doped non-metallic catalysts.

Palladium nanoparticles anchored on Schiff base metal complex derived heteroatom-doped carbon materials for boosting ethanol electrooxidation

Designing appropriate support for noble metal-based catalyst has consistently been an effective strategy to improve the catalytic activity of ethanol electrooxidation reaction (EOR). Here, a novel heteroatom-doped carbon (HDC) material has been prepared by calcination of Schiff base metal complex precursor. The HDC-750 prepared at the optimum temperature (750 °C) has a three-dimensional structure with large specific surface area and unique pores. When the HDC-750 is used as a support for palladium nanoparticles, it can improve the conductivity of catalysts, the permeability of electrolyte and intermediates, and increase the number of anchoring points of palladium nanoparticles. Due to its unique three-dimensional structure and the synergistic enhancement effect of strong metal support interaction between Pd and HDC-750, the Pd/HDC-750 catalyst exhibits high electrochemical active surface area (23.94 m2 gPd−1) and excellent EOR activity (146.3 mA cm−2), which is as high as 2.1 and 3.0 times of that for the Pd/C. After 3600 s durability test, the Pd/HDC-750 shows a high current density of 9.9 mA cm−2, while Pd/C shows only 1.3 mA cm−2.

Facile Approach To Prepare Multiple Heteroatom-Doped Carbon Material from Bagasse and Its Applications toward Lithium-Ion and Lithium–Sulfur Batteries

The constant search for cost-effective and high-performance materials for Li-ion batteries (LIBs) has increased with time. Here, we synthesized low-cost multi-heteroatom co-doped carbon from biowas...

Theory-Driven Design of Electrocatalysts for the Two-Electron Oxygen Reduction Reaction Based on Dispersed Metal Phthalocyanines

Theory-Driven Design of Electrocatalysts for the Two-Electron Oxygen Reduction Reaction Based on Dispersed Metal Phthalocyanines

Graphene Nanosphere as Advanced Electrode Material to Promote High Performance Symmetrical Supercapacitor.

To get carbon electrode with both excellent gravimetric and volumetric capacitances at high mass loadings is critical to supercapacitors. Herein, cracked defective graphene nanospheres (GNS) well meet above requirements. The morphology and structure of the GNS are controlled by polystyrene sphere template/glucose ratio, microwave heating time, and Fe content. The typical GNS with specific surface area of 2794 m2 g-1 , pore volume of 1.48 cm3 g-1 , and packing density of 0.74g cm-3 performs high gravimetric and volumetric capacitances of 529 F g-1 and 392 F cm-3 at 1A g-1 with a capacitance retention of 62.5% at 100 A g-1 in a three-electrode system in 6mol L-1 KOH aqueous electrolyte. In a two-electrode system, the GNS possesses energy density of 18.6Wh kg-1 (13.8Wh L-1 ) at the power density of 504 W kg-1 , which is higher than all reported pure carbon materials in gravimetric energy density and higher than all reported heteroatom-doped carbon materials in volumetric energy density, in aqueous solution, as far as it is known. A structural feature of carbon materials that possess both high energy density and high power density is pointed out here.

Activation of persulfates by carbonaceous materials: A review

• Structural defects and certain O-groups on surface of C material cause activation. • Synergistic effect takes place for heteroatomic C materials to activate persulfates. • Both radical and non-radical pathways are responsible for the activation. • Application of C materials for the activation is limited but have great potential. In recent years, persulfate-based advanced oxidation processes (PS-AOPs) for removal of organic contaminants from water have gained wide attention. Ever-emerging carbonaceous materials, including pristine carbon materials and their derivatives, heteroatom-doped carbon materials, and carbon materials with metal particles, are demonstrated to be effective in the activation of persulfates (peroxymonosulfate (PMS) and peroxydisulfate (PDS)) to generate free radicals or non-radical active species for degradation of the contaminants. In this paper, mechanisms for the activation of persulfates by carbonaceous materials and their composites are analyzed and summarized. In particular, the synergistic effect for activation improvement in the composites or in the hybrid activation systems is explored. Then the influence of the environmental conditions, such as pH, temperature, inorganic anions and dissolved organic matter, on the activation processes are discussed. Deactivation and regeneration of the carbonaceous materials are discussed as well. Finally, the application of these carbonaceous materials in activating persulfates for remediation of contaminated groundwater and treatment of wastewater are reviewed and the challenges for such applications are proposed.

Heteroatoms in Bowl-shaped Polycyclic Aromatic Hydrocarbons: Synthesis and Structures

Nowadays, exploring the chemistry of curved π-conjugated molecules is one of the big trends in organic chemistry. Recently, research interests have been shifted to heteroatom containing analogs. Among these, bowl-shaped π-conjugated molecules with heteroatoms included within their skeletons have gained interest due to their synthetic difficulty and have been developed dramatically as a motif for heteroatom-doped carbon materials. Here, this review highlights analogs based on polycyclic aromatic hydrocarbons, represented by triangulenes, sumanenes and corannulenes, with heteroatoms. These studies have disclosed the effect of heteroatoms in curved π-surfaces.

Ultrathin B, N co-doped porous carbon nanosheets derived from intumescent flame retardant for rechargeable Zn-air battery

Engineering highly efficient and robust porous carbon materials for the oxygen reduction and oxygen evolution reactions (ORR/OER) remains a great challenge for boosting the practical application of metal-air batteries. Herein, we report a carbonization-etching approach to achieve ultrathin B, N co-doped porous carbon nanosheets (BN–PCN) with hierarchically porous structure and large specific surface area (966.46 m2 g−1) using intumescent flame retardant (IFR) system. Owing to its unique structural features, the BN-PCN delivers high electrocatalytic ORR activity with a comparable half-wave potential of 0.84 V and superior stability to those of commercial Pt/C. Moreover, the BN-PCN exhibits a smaller overpotential for OER in comparison with singly doped counterparts, suggesting that the structural properties of BN-PCN play important roles in imparting the electrocatalytic activities of ORR and OER. Furthermore, BN-PCN-driven Zn-air battery demonstrates excellent power density (193.6 mW cm−2) and high energy efficiency. This study offers a promising avenue for designing multiple heteroatom-doped porous carbon materials for clean energy conversion and storage applications.

Atomic metal, N, S co-doped 3D porous nano-carbons: Highly efficient catalysts for HT-PEMFC

A new strategy for fabricating atomically dispersed heteroatom-doped nanoporous carbon materials is reported. Through the self-assembly of dopamine, triblock copolymer F127, and metal ions, different three-dimensional atomic metal-N/S doped carbon catalysts are obtained after pyrolysis. Noble metal salts with ferrous sulfate induce the bimetallic monatomic FeM (M = Pd, Pt) N, S-doped carbon catalysts. Minute amounts of Pt or Pd single atoms in the catalysts greatly improve the oxygen reduction reaction (ORR) activity both in acidic and alkaline conditions. Typically, the obtained Fe, Pt–N/S co-doped carbon (FePt-NSC) catalyst exhibits superior ORR performance with positive half-wave potentials (E1/2) of 0.89 and 0.80 V in alkaline and acidic solutions, respectively. In addition, FePt-NSC displays dominant four electron catalytic process and excellent electrocatalytic stability. The high temperature proton exchange membrane fuel cell (HT-PEMFC) test (160 °C) illustrates that FePt-NSC reaches 0.67 V at 400 mA/cm2 and achieves the peak power density of 628 mW/cm2, better than most of the catalysts reported at the similar conditions. These results indicate the atomic metal-N/S doped porous carbon catalysts to be highly promising low-Pt catalysts for HT-PEMFC.