Dual-doped Carbon Materials Research Articles

Upcycling of electroplating sludge into Fe3C-decorated N,P dual-doped porous carbon via microalgae as efficient sulfur host for lithium–sulfur batteries

Some crystal planes of metal compound nanocrystals play an important role in the anchoring and transformation of lithium polysulfide (LiPSs), which effectively improves the shuttle effect and electrochemical reaction kinetics of LiPSs. While, as a new generation of secondary batteries with great potential, the commercial applications of Li-S batteries are limited by rapid capacity decay due to the shuttle effect of LiPSs and large volume change of sulfur. Herein, nano-Fe3C@N,P dual-doped porous carbon microspheres (Fe3C@NPC) were designed as cathode hosts of Li-S batteries. Fe3C@NPC composite materials were prepared by upcycling mental from electroplating sludge via microalgae. The adsorption transformation of microalgae enables Fe3C nanocrystals of 10–30 nm to be evenly embedded in the N and P dual-doped carbon materials, which makes the crystal planes (220) of Fe3C nanocrystals more involved in the reaction, thus improving the coulomb efficiency and long cycle stability of Li-S battery. Besides, the hierarchically porous spherical structure with high specific surface area not only effectively adapts to the change of sulfur volume during the charging/discharging process, but also significantly increases the electrolyte contact area and shortens the Li ion transport distance. Therefore, Fe3C@NPC, as the multifunctional hosts of sulfur for Li-S batteries, realizes high catalytic activity and strong chemical binding with LiPSs, providing a high reversible coulomb efficiency (> 99%) and a high reversible capacity of 575 mAh g−1 at 1 C after 500 cycles, with low-capacity decay rates of 0.056% per cycle.

Favorable pore size distribution of biomass-derived N, S dual-doped carbon materials for advanced oxygen reduction reaction

Metal-free carbon materials offer prominent performance towards the oxygen reduction reaction (ORR). The pore size distribution of carbons plays the vital role in promoting the electrocatalytic property. Herein, a succession of N, S dual-doped carbons decorated with 3D interpenetrated hierarchically porous structure are successfully obtained through utilizing ZnCl 2 and Zn(OH) 2 as porogens during carbonizing biomass-wastes. The nanopore amounts with specific sizes can be manipulated through changing diverse biomass-wastes as precursors, while different pore sizes can be optimized by tuning the dosage ratios of ZnCl 2 to Zn(OH) 2 . Accompany with the increased amounts of nanopores with sizes of 4.6, 12, 17 and 27 nm, the ORR activity of carbon materials has been significantly promoted. These suitable pore sizes ensure the highly effecient mass transfer through providing abundantly accessible delivery channels and reactive zones for ORR-related intermediates. The optimized catalyst delivers the excellent ORR activity with a half-wave potential of 0.83 V vs. RHE as well as the remarkable long-term stability and methanol resistance ability in alkaline medium. Moreover, two series-connected Zn-air batteries with the catalysts can continuously lighten 216 LEDs over 24 h. The application of biomass-wastes to synthesize N, S dual-doped hierarchical porous carbons is beneficial for achieving the goals of turning waste into treasure. The amounts of pores with sizes of 4, 12, 17 and 27 nm show an apparent control on ORR activity according to biomass-wastes derived carbon materials, achieving the goals of turning waste into treasure and providing a rational guidance in preparing the high-performance electrocatalysts. • Continuously regulating the nanopore amount of carbon materials has been achieved. • The application of biomass-wastes realizes the goal of turning waste into treasure. • The optimized catalyst delivers the impressive ORR catalytic activity. • The assembled Zn-air battery continuously drives 216 LEDs for 24 h. • This work identifies the favorable pore size of carbon materials towards ORR.

Metal-free aerobic oxidation of benzyl alcohols over the selective N, P dual-doped hollow carbon sphere as the efficient and sustainable heterogeneous catalyst under mild reaction condition

Nitrogen and phosphorous dual-doped carbon materials are one the promising candidate for the ecofriendly and metal-free heterogeneous catalytic systems owing to the abundance activated sites which is caused by doping the heteroatoms in the carbonaceous materials. The N, P-dual-doped carbon hollow sphere (HPNC-700) precursor prepared via template-assisted strategy by using the SiO 2 as the hard template in the presence of glucose, phosphoric acid and melamine as C, P, and N source, respectively. The resultant catalyst was obtained by pyrolyzing process at 700 °C under N 2 atmosphere by adding the NaOH solution to remove the template. According to various physicochemical analysis including FE-SEM, TEM, XRD, XPS, and Raman spectroscopy, the catalyst exhibited the desired and acceptable properties. So, based on these outcomes, the catalytic efficiency of the HPNC-700 was evaluated in the selective aerobic oxidation of benzyl alcohols. As expected, the HPNC-700 represented the acceptable proficiency in the mentioned reaction with high TOF value, full conversion (>99%) and also the notable recyclability. • P, N-dual doped carbon hollow spheres were designed for selective aerobic oxidation of benzyl alcohols. • SiO 2 spheres were used as the hard templet to synthesis the hollow spheres. • The heterogeneous metal-free HPNC-700 catalyst represents the high efficiency toward oxidation reaction at mild condition. • The more defects in the carbonaceous caused the more efficiency in the catalytic performance. • By doping The P and N in the sructure of carbon, the activated sites were developed in the synthesized catalyst.

Plasma-engineered organic dyes as efficient polysulfide-mediating layers for high performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted extensive attention as a promising energy storage technology owing to their high theoretical capacity and energy density coupled with high cost efficiency. Despite these advantages, Li-S batteries still face problems in the shuttling behavior of soluble lithium polysulfides and the electrically insulating nature of sulfur, which has motivated considerable efforts toward developing conductive nanomaterials to improve electrochemical performances. In this study, microporous N, S dual-doped carbon materials based on a basic dye compound, methylene blue, were prepared via plasma engineering and carbonization process. Experimental and theoretical investigations revealed that an introduction of the carbon coated separators, denoted as PPMB interlayers, in Li-S batteries resulted in reduced cell polarization and effectively alleviated the lithium polysulfide shuttling behavior, leading to a high specific capacity of 1,329 mAh g−1 and retained specific capacity of 669 mAh g−1 after 100 cycles at 0.3C. This work highlights the potential application of this heteroatom-doped carbon material in Li-S batteries, as well as the viability of dye compound-derived carbon materials in energy storage devices.

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

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.

Nitrogen and sulfur dual-doped hollow mesoporous carbon spheres as efficient metal-free catalyst for oxygen reduction reaction

Developing a cheap and efficient oxygen reduction reaction (ORR) catalyst is one of the emerging issues. The doped carbon materials have attracted much attention due to the controllable and cheap synthesis methods. In this work, the nitrogen and sulfur dual-doped hollow mesoporous carbon sphere (NS-HMCS) has been synthesized through a hard-template method. During the co-polymerization process of dopamine (DA) and cysteamine (CA), the nitrogen (N) and sulfur (S) sites are introduced into the carbon skeleton at the same time, which simplifies the tedious steps in the post-modification of carbon materials. The obtained NS-HMCS-32 exhibits high content of nitrogen about 4.8% and sulfur about 1.4%. NS-HMCS-32 has a high specific surface areas (898 m2 g−1) and a large pore volume (2.99 cm3 g−1). During the ORR measurement, the half-wave potential of NS-HMCS-32 reaches up to 0.77 V vs. RHE. Moreover, NS-HMCS-32 reveals a better durability than commercial Pt/C and 79.2% of current density remains after 9 h chronoamperometry test. This work provides a design idea for dual-doped carbon materials and the obtained NS-HMCS is a potential candidate for metal-free catalyst in fuel cells.

Nitrogen and sulfur dual-doped high-surface-area hollow carbon nanospheres for efficient CO2 reduction

The electrochemical reduction of CO2 (CO2RR) can substantially contribute to the production of useful chemicals and reduction of global CO2 emissions. Herein, we presented N and S dual-doped high-surface-area carbon materials (SZ-HCN) as CO2RR catalysts. N and S were doped by one-step pyrolysis of a N-containing polymer and S powder. ZnCl2 was applied as a volatile porogen to prepare porous SZ-HCN. SZ-HCN with a high specific surface area (1510 m2 g−g1) exhibited efficient electrocatalytic activity and selectivity for CO2RR. Electrochemical measurements demonstrated that SZ-HCN showed excellent catalytic performance for CO2-to-CO reduction with a high CO Faradaic efficiency (~93%) at −0.6 V. Furthermore, SZ-HCN offered a stable current density and high CO selectivity over at least 20 h continuous operation, revealing remarkable electrocatalytic durability. The experimental results and density functional theory calculations indicated that N and S dual-doped carbon materials required lower Gibbs free energy to form the COOH* intermediate than that for single-N-doped carbon for CO2-to-CO reduction, thereby enhancing CO2RR activity.

Activation of graphitic nitrogen sites for boosting oxygen reduction

Carbon materials doped with sulfur (S) and nitrogen (N) are prospective alternatives to Pt-based catalysts as oxygen reduction reaction (ORR) catalyst since they are inexpensive and highly catalytic active. However, the further advancement of catalysts is greatly hindered for its unclear and equivocal catalytic sites. Here, using density functional theory studies, we find that those inactive carbon atoms next to graphitic N become ORR catalytic sites after S doping, which is distinctly different from N-doped carbon materials where catalytic sites are introduced by pyridinic N. The electrochemical results show that increasing the content of graphitic N can lead to higher catalytic activity for S and N dual-doped carbon materials, which exhibits higher turnover frequency towards ORR than that of N-doped carbon materials. This work provides insights for further advancement of electrocatalysts via heteroatom doping.

N, S Dual-Doped Carbon Derived from Dye Sludge by Using Polymeric Flocculant as Soft Template.

Dye sludge is a major by-product and it will bring critical environmental problems in the textile industry. In this study, dicyandiamide formaldehyde resin (DFR) is used as an effective flocculating agent for the removal of anionic dyes from textile dye wastewater. Employing dye-contaminated sewage sludges as precursors, N, S dual-doped carbon materials are successfully synthesized by using DFR as a soft template. The specific surface area, morphology, and pore structure of the resulting annealed products can be easily controlled by changing the DFR content of the dye sludge. The oxygen reduction reaction performance of optimal carbon material (N, S-DF-2) is close to commercial 20% Pt/C in alkaline medium, including onset potential (0.98 V), half-wave potential (0.82 V), as well as limiting current density (5.46 mA·cm−2). Furthermore, it also shows better durability and crossover resistance. In addition, N, S-DF-2 exhibits a large specific capacitance (230 F·g−1 at 1 A·g−1) and super capacitance retention (nearly 98% at 10 A·g−1) after 2500 cycles as supercapacitors electrodes. This work opens up a new method to take full advantage of organic polymeric flocculant as a soft template to prepare N, S dual-doped carbon materials, which will be beneficial for the reuse and recycling of sewage sludge, as well as for the production of good quality energy conversion and storage materials.

Light metal decoration on nitrogen/sulfur codoped graphyne: An efficient strategy for designing hydrogen storage media

Nitrogen/sulfur dual doped carbon materials have attracted a great deal of interest due to their fascinating applications in lithium ion batteries, hydrogen storage, and oxygen reduction reactions. Here, the hydrogen storage capacity of NS dual-doped graphyne (GYNS) decorated with Li or Na is theoretically explored. The NS-codoping leads to greater charge transfer and stronger binding between the alkali metal and graphyne surface giving rise to enhanced hydrogen storage capacity. We showed that the NS-codoping increases the hydrogen storage capacities of Li-decorated and Na-decorated GY by almost 30% and 60%, respectively. At high NS concentration, the hydrogen uptake capacities can reach to 8.98 wt% and 9.34 wt% for double-side Li- decorated GYNS and Na-decorated GYNS. Moreover, the average adsorption energies per H2 are −0.27 eV for 2Li/GYNS(33.3%) and −0.26 eV for 2Na/GYNS(33.3%) which lie in desirable range for practical applications at ambient conditions.

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 fabricate nitrogen and sulfur co-doped carbon microsphere (NSCM) by using thiourea as dopant. The N/S 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°C (NSCM-800) achieves a capacitance of 277.1Fg−1 at a current density of 0.3Ag−1 in 6.0molL−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 cycles at a current density of 3.0Ag−1.

N- and S-doped mesoporous carbon as metal-free cathode catalysts for direct biorenewable alcohol fuel cells

N and S dual-doped carbon materials, N-S-CMK-3, are fabricated with >1000 m2 g−1 surface area and uniform mesoporous and macroporous structures, and exhibit outstanding ORR activity and durability in both half cell and direct biorenewable alcohol fuel cell tests.

One-step pyrolytic synthesis of nitrogen and sulfur dual-doped porous carbon with high catalytic activity and good accessibility to small biomolecules.

As one of promising catalysts that contain high density of active sites, N doped carbons have been extensively researched, while the reports for N, S dual-doped carbon materials are far less exhaustive. Herein, devoid of activation process and template, N, S dual-doped porous carbon (N-S-PC) was prepared for the first time via one-step pyrolysis of sodium citrate and cysteine. Possessing unique porous structure and large pore volume as well as good accessibility, N-S-PC demonstrates significantly improved electrocatalytic activity toward oxidation of ascorbic acid (AA), dopamine (DA), and uric acid (UA). In the coexisting system, the peak potential separation between AA and DA is up to 251 mV, which is much larger than for most of the other carbons. On the basis of large potential separation and high current response, selective and sensitive simultaneous determination of AA, DA, and UA was successfully accomplished by differential pulse voltammetry, displaying a linear response from 50 to 2000 μM, from 0.1 to 50 μM, and from 0.1 to 50 μM with a detection limit (S/N = 3) of 0.78, 0.02, and 0.06 μM. This work highlights the importance of N, S dual doping and hierarchical porous carbons for efficient catalysis.