Nitrogen Co-doped Carbon Materials Research Articles

Carbon materials co-doped with nitrogen and sulfur for highly efficient catalytic activity in oxygen reduction and evolution

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) represent crucial steps in the functioning of fuel cells and metal-air batteries. Designing bifunctional oxygen electrode catalysts with high activity for both ORR and OER remains an immense challenge. In this study, we address this challenge by employing in-situ polymerization to design nitrogen and sulfur co-doped carbon materials (NSCs). The resulting NSC-1000–3 exhibits an onset potential of 1.03 V vs. RHE and a half-wave potential (E1/2) of approximately 0.89 V during ORR in an alkaline solution. When compared to commercial Pt/C, it demonstrates a positive shift of 60 mV in the half-wave potential. Furthermore, NSC-1000–3 displays outstanding oxygen evolution performance. At a current density of 10 mA cm−2, its performance matches that of RuO2. This material demonstrates exceptional performance in both ORR and OER, showcasing the synergistic doping effects of nitrogen and sulfur.

Waste Tire Derived Carbon Support for Non-Platinum-Group Metal Catalyst Materials for Oxygen Reduction Reaction in Alkaline Medium

Extensive use of non-renewable energy sources and excessive accumulation of hard-to-recycle waste, such as end-of-life tires, are among the most significant environmental problems today. For a more sustainable future, it is essential to find alternative solutions to energy and special waste management. For example, waste tires can be used to synthesize high-tech porous carbon materials, which can be used as a carbon support in fuel cell catalysts. [1] While fuel cells offer a promising alternative to some fossil fuel-based technologies, low temperature fuel cell catalysts rely on expensive platinum. Non-platinum-group metal (NPGM) catalysts, such as iron and nitrogen co-doped carbon materials are good contenders to platinum-based catalysts for the oxygen reduction reaction. Synthesizing porous carbon materials for more economically viable NPGM fuel cell catalysts could provide one way to use waste tires more sustainably and lower the cost of efficient fuel cell catalysts.For this work, a carbon material was synthesized by pyrolyzing tire granules (Imdex A/S) at 1000 °C for three hours in Ar [2]. Based on this carbon material, several iron and nitrogen co-doped catalyst materials were synthesized using Fe(NO3)3 as the iron source, dicyandiamide or guanidine as the nitrogen source, and ZnCl2 as a pore modifier. All synthesized materials were acid washed overnight to remove redundant elements such as Zn from the pore modifier and various impurities originating from the tire granules (mainly Si, S, Ca, and Zn). Finally, the materials pyrolyzed for a second time. The pyrolysis temperature, choice of nitrogen compound, and precursor ratios were varied for the syntheses described in this work.The NPGM catalyst materials were characterized by various physical and electrochemical methods to describe the relationship between the catalyst structure and the activity of the oxygen reduction reaction. SEM and SEM-EDX were used to evaluate the morphology and composition of the catalyst materials. N2 sorption data suggested that the specific surface area ranged from 77 to 194 m2 g-1 for all materials. Electrochemical characterization was performed in 0.1M KOH solution using the rotating disk electrode method. The highest onset potential (Eon = 920 mV vs RHE) was reached by a material using guanidine as the nitrogen source pyrolyzed at 900 °C, which is comparable to other recently described NPGM materials [3], including waste-tire derived NPGM catalysts [4]. Acknowledgements: This work was supported by the following projects: PRG676 “ Development of express analysis methods for micro-mesoporous materials for Estonian peat derived carbon supercapacitors” (1.01.2020- 31.12.2024)"Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” (TK141) (1.01.2016−1.03.2023) References [1] J. S. Gnanaraj et al., Sustainability 10(8), 2840 (2018)[2] J. Laanemäe, R. Jäger, P. Teppor, O. Volobujeva, and Enn Lust, ECS Transactions, 108, p. 39 (2022)[3] R. Gutru et al., International Journal of Hydrogen Energy, 47 (2022)[4] M. Muhyuddin et al., Electrochemica Acta, 433, 141254 (2022)

Theory‐guided Design of Atomically Dispersed Dual‐Metal Catalysts for Superior Oxygen Reduction Reaction Activity

AbstractThe widespread application of electrochemical energy conversion devices, such as proton exchange membrane fuel cells, is hindered by the kinetically sluggish oxygen reduction reaction (ORR) at the cathode. Transition‐metal and nitrogen codoped carbon materials (TM−N−C) are among the most promising catalysts to solve this problem. Particularly, dual‐metal TM−N−C have already displayed excellent performance. However, further knowledge on the reaction mechanism and the structure−activity relationship is still required. In this study, we established three dual‐metal TM−N−C models (FeMn−N−C, FeCo−N−C, and FeNi−N−C) to investigate the electronic interaction between the metallic sites and their corresponding adsorption strength for oxygenated intermediates in ORR electrocatalysis. Then, using density functional theory calculations, we determined that the ORR activity of the dual‐metal TM−N−C models followed the order of FeCo−N−C > FeNi−N−C > FeMn−N−C. We confirmed the theoretically predicted activity by synthesizing atomically dispersed FeMn−N−C, FeCo−N−C, and FeNi−N−C catalysts using metal‐organic framework precursors, among which FeCo−N−C showed the best results in terms of ORR onset potential and half‐wave potential (0.92 and 0.81 V vs. the reference hydrogen electrode in 0.1 M HClO4, respectively.). The results demonstrate the feasibility of the theory‐guided rational design of efficient dual‐metal catalysts for ORR electrocatalysis.

Edge-rich Co/N-doped 3D nanosheet stacked carbon as an efficient dual-function electrocatalyst for rechargeable Zn-air battery

The development of high-efficiency oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) dual-function electrocatalysts based on transition metal and nitrogen co-doped carbon material is vital to the development of rechargeable Zn-air battery. In this work, dual-function oxygen electrocatalysts of 2D graphene-like (NC) and 3D nanosheet stacked carbon (CNC) derived from Zn-based zeolite-like metalorganic frameworks were prepared from the complex of imidazole-4, 5-dicarboxylic acid (4,5-Imdc) with only zinc nitrate (4,5-Imdc-Zn) or zinc and cobalt nitrate (4,5-Imdc-ZnCo). Morphology and catalytic activity of NC and CNC were studied in detail. After high temperature calcination, 4,5-Imdc-Zn developed into a 2D graphene-like structure (NC). While derivative of 4,5-Imdc-ZnCo appears a 3D nanosheet stacked (CNC) structure induced by a “pinning effect” of the existing Co ions. With increased defects, edges and Co-Nx active sites compared to NC, CNC shows more excellent electrocatalytic activity.

A carbon catalyst doped with Co and N derived from the metal-organic framework hybrid (ZIF-8@ZIF-67) for efficient oxygen reduction reaction

Carbon-based catalysts for the oxygen reduction reaction (ORR) are considered potential substitutes for the expensive platinum-based catalysts. Recently, transition metal and nitrogen co-doped carbon materials (M-N-C) have attracted much attention from researchers due to their low cost and excellent activity. A cobalt- and nitrogen-co-doped porous carbon material (Co-N@CNT-C800) was prepared by the simple one-step pyrolysis of a star fruit-like MOF hybrid (ZIF-8@ZIF-67) at 800 °C. It consisted of CNTs with substantial Co and N co-doping and had a large surface area (428 m2·g−1). It had an excellent half-wave potential and good current density in alkaline media in the ORR with values of 0.841 V and 5.07 mA·cm−2, respectively. Compared with commercial Pt/C materials it also had excellent electrochemical stability and methanol tolerance. This research provides an effective way to fabricate low cost, high activity electrocatalysts for use in energy conversion.

In situ-synthesized Co and N-doped mesoporous hollow silica spheres for the selective oxidation of ethylbenzene.

Transition metal and nitrogen co-doped carbon materials (M-N-C) have attracted great attention in the field of catalysis due to their high atomic utilization and outstanding catalytic performance. Herein, a series of Co and N-doped carbon catalysts (Co-N-C@mSiO2-x) were successfully prepared by pyrolysis of cobalt porphyrins in situ synthesized in the cavity of mesoporous hollow silica spheres according to a ship-in-bottle method. The optimal catalyst exhibited excellent catalytic performance for the selective oxidation of ethylbenzene, with 95.5% conversion for ethylbenzene and 98.9% selectivity toward acetophenone. In combination with characterization techniques, acid treatment experiments and KSCN poisoning tests, the successful synthesis of cobalt-porphyrins in hollow silica spheres was demonstrated, and the excellent performance of Co-N-C@mSiO2-0.10 was attributed to the more acid-resistant Co-Nx species as the main metal active center. In addition, the N-containing groups could significantly facilitate the conversion of ethylbenzene. This work is expected to provide a straightforward and green approach to design metal and N co-doped carbon materials.

Tailored imidazolium tetraphenylborate salts for the design of boron, nitrogen co-doped carbon materials as high-performance anodes for fast-rate monovalent ion batteries

Boron, nitrogen co-doped carbons prepared from original imidazolium tetraphenylborate salts demonstrated high rate capabilitiesversusLi+/Li.

Biomass-derived nitrogen and sulfur co-doped sheet-like porous carbon for high-performance supercapacitors

Nitrogen and sulfur co-doped porous carbon materials with excellent electrochemical performance were prepared using a one-step carbonization and activation method.

Hollow polyhedral Fe-N-C nanostructures derived from ZIF-8 highlighting markable morphology effect on electrochemical oxygen reduction and carbon dioxide reduction

Iron and nitrogen co-doped carbon materials (Fe-N-C) have been identified as one promising class of electrocatalysts toward both electrochemical oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR), which are profoundly influenced by both intrinsic and extrinsic factors. Herein a well-defined hollow polyhedral Fe-N-C nanostructure (FeNC-H) is obtained by pyrolyzing ZIF-8 precursor involving FeCl3 absorption and KOH treatment. In comparison, direct pyrolysis of FeCl3-absorbed ZIF-8 only leads to densely fused carbon particles (FeNC-R). Albeit similar pore characteristics between FeNC-H and FeNC-R, FeNC-H exhibits superior ORR and CO2RR performance to FeNC-R due to its markable hollow morphology effect. In O2-saturated 0.1 M KOH solution, FeNC-H delivers an onset potential of 0.966 V (vs. RHE) and a half-wave potential of 0.865 V (vs. RHE), surpassing the benchmark Pt/C. Meanwhile, FeNC-H achieves 91.8 % FE of CO at − 0.5 V (vs. RHE) in CO2-saturated 0.5 M KHCO3 solution. It is found that the unique hollow morphology endows FeNC-H with high surface area, large pore volume and fast mass transfer kinetics, thus boosting both ORR and CO2RR.

Ruthenium nanoparticles loaded on N/P co-doped carbon sphere derived from sphere cross-linked hydrogel for highly improved hydrogen evolution reaction

Developing efficient and stable catalysts for hydrogen evolution reaction (HER) in electrolysis water is crucially significant but challenging. With enhanced hydrogen bonding energy as well as a reasonable price, ruthenium-based catalysts are one of the promising catalytic materials to replace Pt for HER. In this work, nitrogen and phosphorus co-doped carbon materials supporting ruthenium nanoparticles (Ru/NPC) are prepared by two pyrolysis processes and then used as a HER efficient catalyst. In alkaline media, Ru/NPC-2 requires only a low overpotential of 64 mV to achieve the current density of 10 mA cm−2, and shows a small Tafel slope of about 76 mV dec-1 and long-lasting stability. The introduction of Ru effectively increases the electrochemical active area of the catalytic material as well as promotes sufficient contact between the surface of the catalyst and the electrolyte, thereby exposing more active sites. In addition, the normalized results show that the synergistic effect among phosphorus, nitrogen, and ruthenium effectively enhances the intrinsic activity of active sites. Therefore, Ru/NPC exhibits outstanding HER catalytic performance. This work fully demonstrates the advantages of non-metallic element-doped carbon supports in enhancing the activity of ruthenium, and has an important reference for the subsequent development of carbon-supported high-efficiency electrocatalysts.

Formation of Nitrogen-Coordinated Metal Sites (M = Fe, Co) via Solution-Phase Coordination on Nickel- And Nitrogen-Co-Doped Carbon Templates with Metal Vacancy-Nx Sites

Platinum group metal-free catalysts based on transition metal and nitrogen co-doped carbon materials are gaining attention for their applications in electrocatalysis. Nitrogen-coordinated metal sites (MNx) have been identified as the main active sites in PGM-free catalysts. Current synthetic approaches rely on the high-temperature treatment to introduce targeted electroactive MNx sites into the carbon matrix. In this study, we demonstrated the formation of MNx sites on Ni- and N-co-doped carbon templates via the solution-phase coordination with target metal ions, including Fe2+, Fe3+, and/ Co2+. The formation of MNx sites was confirmed via a combined approach of various physical characterization techniques, elemental analysis, and electrochemical analysis. The results indicate that the metal-vacancy-Nx sites in the template can coordinate with target ions to form electrochemically active MNx sites. By varying heat-treatment temperature, the amount of FeNx sites formed via coordination with Fe2+ ion can be tuned and correlated with the change of activity toward oxygen reduction reaction. The amount of MNx sites formed via solution-phase coordination with various ions followed the sequence of Co2+ > Fe2+ > Fe3+. These findings may further guide the future development of MNx-C electrocatalysts through this solution-phase coordination approach.

Facile self-template synthesis of sulphur and nitrogen-codoped nanoporous carbon derived from functionalized polyethersulfone (PES) and its application for supercapacitors

• A self-template approach to prepare N and S co-doped porous carbon is proposed. • The SNC-800 shows a high specific capacitance (240F/g). • The device (SNC-800//SNC-800) exhibits superior supercapacitive behavior to many carbon materials. A Novel Sulphur and Nitrogen-codoped carbon (SNC-800) material was prepared by pyrolysis of functionalized Polyethersulfone (PES) under 800℃, which was synthesized by one-pot polymerization. The SNC-800 was served as electrode material and showed a high specific capacitance (240 F/g). The capacitance retention of SNC-800 is as high as 91.6% after 10,000 cycles. The device base on delivered a high energy density (23.5 Wh/kg) with power density (800 W/kg). These results suggest that SNC-800 is a promising electrode material for supercapacitors.

A novel one-step calcination tailored single-atom iron and nitrogen co-doped carbon material catalyst for the selective reduction of CO2 to CO

Single atom Fe-N-C based electrocatalysts are the most promising candidates for industrial applications of reduction of CO2. However, preparation of Fe-N-C catalyst often involves complex procedures and expensive precursors/reagents. In this work, we developed a novel one-step calcination method to tailor single-atom Fe-N-C catalyst for CO2 reduction. The maximum Faraday efficiency of CO (FECO) and the Tafel slope of Fe-N-C material was 73% and 68 mv dec−1, respectively, which was much higher than that of the pristine N-C material. The CO2 electroreduction products were CO and H2 with a total Faraday efficiency of 100%, indicating that the Fe-N-C material had high selectivity on CO2 reduction to CO. The designed Fe-Nx structure on the Fe-N-C material acted as a highly active site, and the abundant functional groups and microporous structure resulted in high catalytic performance of Fe-N-C material. This work demonstrates that the tailored single-atom Fe-N-C catalyst by one-step calcination has broad application prospects in the electrochemical reduction of CO2.

(Digital Presentation) Oxygen Reduction Reaction on Waste Tire Derived Carbon Material and Synthesized Non-Platinum Group Metal Catalysts in Alkaline Solution

Over the past decades, a considerable amount of work has been put into replacing expensive Pt in oxygen reduction reaction (ORR) catalysts for use in fuel cells, such as with Fe or Co and nitrogen co-doped carbon materials [1-3]. At the same time, a major environmental issue is the lack of adequate methods for repurposing or recycling waste tires. Herein, it was investigated whether waste tires could be used as a source of carbon for synthesizing ORR catalysts.To prepare the carbon support, waste tire granules were pyrolyzed at 1000 °C for three hours in Ar. This material was then used to synthesize four non-platinum-group metal (NPGM) catalysts via dry ball-milling [2] and wet synthesis [2, 3] methods. FeSO4∙7H2O or Co(NO3)2·6H2O salts and 2,2’-bipyridine were used as precursors. Wet synthesis required the precursors to be dissolved in water and mixed with the carbon material, after which the solution was dried. For the dry method, all precursors were mixed and ball-milled for one hour. The products of both synthesis methods were subsequently pyrolyzed at 800 °C for 1.5 h in Ar.All materials were characterized using HR-SEM, SEM-EDX, and nitrogen sorption methods. The materials were heterogeneous and contained additives commonly present in tires as constituents of tire filler materials or residual products of tire production (Si, S, Ca, and Zn). All materials exhibited low porosity and a rather low specific surface area (SBET = 92 to 150 m2 g-1).Electrochemical analyses were carried out in an O2 saturated 0.1M KOH solution using the rotating disk electrode method. Although the carbon support on its own did not show significant activity toward the ORR, the modified Co-N/C and Fe-N/C catalysts demonstrated substantially higher onset potentials (∆Eonset ~150 mV). The best electrochemical activity was achieved by the Co-N/C material synthesized using the wet method. These results show that waste tire-derived carbon materials can be used to successfully synthesize NPGM catalysts suitable for application in fuel cells. Acknowledgements This work was supported by PRG676 "Development of express analysis methods for micro-mesoporous materials for Estonian peat derived carbon supercapacitors" (1.01.2020- 31.12.2024), TK141 "Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics" (1.01.2016−1.03.2023), and LLTKT20148 "Production of Polymer Electrolyte Membrane Fuel Cell" (10.02.2020−9.07.2021) References [1] F. Roncaroli, E. S. Dal Molin, F. A. Viva, M. M. Bruno, and E. B. Halac, Electrochimica Acta, 174, p. 66 (2015)[2] P. Teppor, R. Jäger, E. Härk, S. Sepp, M. Kook, O. Volobujeva, P. Paiste, Z. Kochovski, I. Tallo, and E. Lust, J. Electrochem. Soc., 167, 054513 (2020)[3] R. Jäger, P. E. Kasatkin, E. Härk, P. Teppor, T. Romann, R. Härmas, I. Tallo, U. Mäeorg, U. Joost, P. Paiste, K. Kirsimäe, and E. Lust, J. Electroanal. Chem., 823, p. 593 (2018)

(Digital Presentation) The Optimization of Polypyrrole Concentration to Synthesize Hollow Fe, Co, and Nitrogen Doped Carbon Spheres with Improved Oxygen Reduction Reaction Performance

Transition metal and nitrogen co-doped carbon materials (M-N-C, M=Fe, Co, Ni, etc.) have recently emerged as front runners to replace commercial Pt/C for the oxygen reduction reaction (ORR) due to their natural availability and excellent electrocatalytic activity. The development of M-N-C materials with optimized active sites using a secondary nitrogen source has attracted a lot of attention as ORR catalysts for their high activity and excellent durability. Polypyrrole (PPy) has become an attractive secondary nitrogen source for increased nitrogen doping and metal dispersion. Herein, we developed hollow Fe, Co, and nitrogen-doped carbon (H-FeCo-NC) spheres using the composites of metal-organic frameworks (MOFs) materials and PPy. Based on X-ray absorption fine spectroscopy analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy, the active centers and the role of PPy for ORR catalytic performance are explored. The H-FeCo-NC not only displayed remarkable ORR performance in alkaline media, with a half-wave potential of 0.903 V, but also showed excellent stability and durability. The results outperformed the commercial Pt/C catalyst, demonstrating the potential of utilizing PPy for improved ORR performance.

Metal-Organic Framework-Derived Graphene Mesh: a Robust Scaffold for Highly Exposed Fe-N4 Active Sites toward an Excellent Oxygen Reduction Catalyst in Acid Media.

This study demonstrates a special ultrathin N-doped graphene nanomesh (NGM) as a robust scaffold for highly exposed Fe-N4 active sites. Significantly, the pore sizes of the NGM can be elaborately regulated by adjusting the thermal exfoliation conditions to simultaneously disperse and anchor Fe-N4 moieties, ultimately leading to highly loaded Fe single-atom catalysts (SA-Fe-NGM) and a highly exposed morphology. The SA-Fe-NGM is found to deliver a superior oxygen reduction reaction (ORR) activity in acidic media (half-wave potential = 0.83 V vs RHE) and a high power density of 634 mW cm-2 in the H2/O2 fuel cell test. First-principles calculations further elucidate the possible catalytic mechanism for ORR based on the identified Fe-N4 active sites and the pore size distribution analysis. This work provides a novel strategy for constructing highly exposed transition metals and nitrogen co-doped carbon materials (M-N-C) catalysts for extended electrocatalytic and energy storage applications.

KOH activated nitrogen and oxygen co-doped tubular carbon clusters as anode material for boosted potassium-ion storage capability

Carbon nanomaterials have become a promising anode material for potassium-ion batteries (KIBs) due to their abundant resources, low cost, and excellent conductivity. However, among carbon materials, the sluggish reaction kinetics and inferior cycle life severely restrict their commercial development as KIBs anodes. It is still a huge challenge to develop carbon materials with various structural advantages and ideal electrochemical properties. Therefore, it is imperative to find a carbon material with heteroatom doping and suitable nanostructure to achieve excellent electrochemical performance. Benefiting from a Na2SO4 template-assisted method and KOH activation process, the KOH activated nitrogen and oxygen co-doped tubular carbon (KNOCTC) material with a porous structure exhibits an impressive reversible capacity of 343 mAh g−1 at 50 mA g−1 and an improved cyclability of 137 mAh g−1 at 2 A g−1 after 3000 cycles with almost no capacity decay. The kinetic analysis indicates that the storage mechanism in KNOCTC is attributed to the pseudocapacitive process during cycling. Furthermore, the new synthesis route of KNOCTC provides a new opportunity to explore carbon-based potassium storage anode materials with high capacity and cycling performance.

Activity descriptor of Ni,N-Codoped carbon electrocatalyst in CO2 electroreduction reaction

• Well-defined Ni,N-C catalysts with finely tunable N species were developed. • The correlation between the content of N specie and CO 2 RR activity was built. • The ratio of Ni-N specie can be used as an activity descriptor of Ni,N-C catalysts. • The universality of activity descriptor for Ni,N-C catalysts was confirmed. Nickel, nitrogen-codoped carbon materials (Ni,N-C) are flourishing as high-efficiency electrocatalysts for CO 2 electroreduction reaction (CO 2 RR). Nevertheless, the preparation of Ni,N-C electrocatalysts with high performance towards CO 2 RR is still blind, without any guidelines, due to the lack of defined and available activity descriptor. Herein, we explored the correlation between the ratio of N species and CO 2 RR activity with taking a series of well-defined Ni,N-C materials as representative electrocatalysts. By smartly utilizing the ratio of Ni-N specie as an activity descriptor, the correlation between the ratio of N specie (Ni-N) and CO partial current density over all samples presents a well volcanic trend. At the optimal ratio of Ni-N specie, a high CO Faradaic efficiency (FE) of 94.8 % can be achieved with a good stability for 29 h. More significantly, the activity range for a library of Ni,N-C electrocatalysts for CO 2 RR is distinctly divided according to the activity descriptor.

Selective Aerobic Oxidation of Csp3-H Bonds Catalyzed by Yeast-Derived Nitrogen, Phosphorus, and Oxygen Codoped Carbon Materials.

Nitrogen, phosphorus, and oxygen codoped carbon catalysts were successfully synthesized using dried yeast powder as a pyrolysis precursor. The yeast-derived heteroatom-doped carbon (yeast@C) catalysts exhibited outstanding performance in the oxidation of Csp3-H bonds to ketones and esters, giving excellent product yields (of up to 98% yield) without organic solvents at low O2 pressure (0.1 MPa). The catalytic oxidation protocol exhibited a broad range of substrates (38 examples) with good functional group tolerance, excellent regioselectivity, and synthetic utility. The yeast-derived heteroatom-doped carbon catalysts showed good reusability and stability after recycling six times without any significant loss of activity. Experimental results and DFT calculations proved the important role of N-oxide (N+-O-) on the surface of yeast@C and a reasonable carbon radical mechanism.

Metal-Organic Framework Derived Zinc and Nitrogen Co-Doped Porous Carbon Materials for High Performance Zinc-Ion Hybrid Supercapacitors

Metal-Organic Framework Derived Zinc and Nitrogen Co-Doped Porous Carbon Materials for High Performance Zinc-Ion Hybrid Supercapacitors