Search Results (88)

The development of cost-effective and scalable air/oxygen electrode materials is crucial for the advancement of Zn–air batteries (ZABs). Porous carbon materials doped with heteroatoms have attracted considerable attention in energy and environmental fields because of their tunable nanoporosity and high electrical conductivity. In this work, we report the synthesis of a three-dimensional (3D) N and P co-doped porous carbon (PA@pDC-1000), derived from a conjugated polyaniline–phytic acid polymer. The cross-linked, rigid conjugated polymeric framework plays a crucial role in maintaining the integrity of micro- and mesoporous structures and promoting graphitization during carbonization. As a result, the material exhibits a hierarchical pore structure, a high specific surface area (1045 m² g⁻¹), and a large pore volume (1.02 cm³ g⁻¹). The 3D N, P co-doped PA@pDC-1000 catalyst delivers a half-wave potential of 0.80 V (vs. RHE) and demonstrates a higher current density compared to commercial Pt/C. A primary ZAB utilizing this material achieves an open-circuit voltage of 1.51 V and a peak power density of 217 mW cm⁻². This metal-free, self-templating presents a scalable route for the generating and producing of high-performance oxygen reduction reaction catalysts for ZABs. Full article

Hierarchical porous N-doped carbon spheres featuring a combination of micropores, mesopores and macropores as well as tuneable properties were synthesised using dopamine as a carbon precursor and triblock copolymers (F127, P123 and F127/P123 composites) as templates via direct polymerisation-induced self-assembly. The structures and textures of these materials were characterised using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption–desorption isotherm analysis, Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The sample synthesised at an F127:P123 molar ratio of 1:3 (NCS-FP3) exhibited the highest surface area (463 m²/g) and pore volume (0.27 cm³/g). The hydrophobic/hydrophilic molar ratios of the templates were adjusted to control the morphology of the corresponding micelles and hence the porous structures and morphologies of the carbon spheres, which exhibited high CO₂ capture capacities (2.90–3.46 mmol/g at 273 K and 760 mmHg) because of their developed microporous structures and N doping. Additionally, NCS-FP3 exhibited an outstanding electrochemical performance, achieving a high specific capacitance (328.3 F/g at a current density of 0.5 A/g) and outstanding cycling stability (99.2% capacitance retention after 10,000 cycles). These high CO₂ capture and electrochemical performances were ascribed to the beneficial effects of pore structures and surface chemistry features. Full article

Oxidative dehydrogenation (ODH) of ethanol to acetaldehyde is an important production process. However, it still suffers from low deactivation, selectivity, and high costs. Herein, we developed a new strategy for preparing mesoporous nitrogen-doped carbon catalysts by carbonization of phenolic resin with silica as a hard template. The catalyst demonstrated an impressive acetaldehyde selectivity of over 76% at 270 °C for 25 h during the ODH of ethanol to acetaldehyde. Mechanistic studies have shown that the two carbon atoms in adjacent C=O groups are replaced by nitrogen atoms in the N₀-Gra-O structural unit. The C=O functional group on the surface of the catalyst is the active center for the ODH of ethanol to acetaldehyde, and the introduction of nitrogen atoms can reduce the adsorption capacity of acetaldehyde molecules at the active site (ΔG values can be reduced by 0.11–0.45 eV), enabling rapid desorption of the product and avoiding the problem of excessive oxidation, thereby improving the selectivity of acetaldehyde. This work reveals the structure–activity relationship between active sites and selective regulation of nitrogen-doped carbon-based catalysts for the ODH of ethanol, providing a theoretical basis for the development of efficient non-metallic carbon-based catalysts. Full article

Ordered mesoporous carbon materials (OMCMs) are widely used as high-performance electrode materials due to their uniform pore structure, excellent electrical conductivity, and good stability. In this paper, three OMCMs with controllable N content were prepared by a nanocasting method using Fe₃O₄ nanocrystals as the template and organic ligands as the carbon source. By adopting a ligand exchange strategy, oleic acid, oleic amine, and octyl amine were successfully capped onto the Fe₃O₄ nanocrystals, respectively, which allowed the rational control of the elemental composition of OMCMs at the molecular level. Further characterizations revealed that the nitrogen content of the resulting OMCMs increased as the proportion of nitrogen atoms in the ligand increased, while the order of the porous structure decreased as the hydrocarbon chain length decreased. This study demonstrates that both the N-doping content and the order of the OMCMs are influenced by the N-containing ligand. This finding will provide a fundamental aspect for their further applications as high-performance electrode and catalytic materials in the field of electrochemistry. Full article

Carbon is predominantly used in zinc-ion hybrid capacitors (ZIHCs) as an electrode material. Nitrogen doping and strategic design can enhance its electrochemical properties. Melamine formaldehyde resin, serving as a hard carbon precursor, synthesizes nitrogen-doped porous carbon after annealing. Incorporating transition metal catalysts like Ni, Co, and Fe alters the morphology, pore structure, graphitization degree, and nitrogen doping types/proportions. Electrochemical tests reveal a superior capacitance of 159.5 F g⁻¹ at a scan rate of 1 mV s⁻¹ and rate performance in Fe-catalyzed N-doped porous carbon (Fe-NDPC). Advanced analysis shows Fe-NDPC’s high graphitic nitrogen content and graphitization degree, boosting its electric double-layer capacitance (EDLC) and pseudocapacitance. Its abundant micro- and mesopores increase the surface area fourfold compared to non-catalyzed samples, favoring EDLC and fast electrolyte transport. This study guides catalyst application in carbon materials for supercapacitors, illuminating how catalysts influence nitrogen-doped porous carbon structure and performance. Full article

Converting carbon dioxide (CO₂) into solar fuels through photocatalysis represents an appealing approach to tackling the escalating energy crisis and mitigating the greenhouse effect. In this study, using melamine–formaldehyde (MF) nanospheres as a nitrogen source, a N element was simultaneously doped into the TiO₂ nanoparticle structure supported by carbon hollow spheres using a one-step carbonization method to form a heterojunction N-CHS@N-TiO₂ (marked as (N-(CHS@TiO₂)). The composite showed superior photocatalytic activity in reducing CO₂ compared with TiO₂ and N-CHS: after 6 h of visible light irradiation, the CO yield was 4.3 times that of N-CHS and TiO₂; 6 h of UV irradiation later, the CO yield reached 2.6 times that of TiO₂ and 7 times that of N-CHS. The substantial enhancement in photocatalytic activity was attributed to the nitrogen simultaneously doped carbon hollow spheres and TiO₂, mesoporous structure, small average TiO₂ crystal size, large surface areas, and the heterostructure formed by N-CHS and N-TiO₂. The UV-vis diffuse reflectance spectra (DRS) exhibit a significant improvement in light absorption, attributed to the visible-light-active carbon hollow sphere and the N element doping, thereby enhancing solar energy utilization. Full article

Developing highly active and durable non-noble metal catalysts is crucial for energy conversion and storage, especially for proton exchange membrane fuel cells (PEMFCs) and lithium-oxygen (Li-O₂) batteries. Non-noble metal catalysts are considered the greatest potential candidates to replace noble metal catalysts in PEMFCs and Li-O₂ batteries. Herein, we propose a novel type of non-noble metal catalyst (Fe-Hf/N/C) doped with Hf into a mesoporous carbon material derived from Hf-ZIF-8 and co-doping with Fe and N, which greatly enhanced the activity and durability of the catalyst. When applied in the cathode of PEMFCs, the current density can reach up 1.1 and 1.7 A cm⁻² at 0.7 and 0.6 V, respectively, with a maximum power density of 1.15 W cm⁻². The discharge capacity of the Li-O₂ batteries is up to 15,081 mAh g⁻¹ with Fe-Hf/N/C in the cathode, which also shows a lower charge overpotential, 200 mV lower than that of the Fe/N/C. Additionally, the Fe-Hf/N/C catalyst has demonstrated better stability in both PEMFCs and Li-O₂ batteries. This reveals that Hf can not only optimize the electronic structure of iron sites and increase the active sites for the oxygen reduction reaction, but can also anchor the active sites, enhancing the durability of the catalyst. This study provides a new strategy for the development of high-performance and durable catalysts for PEMFCs and Li-O₂ batteries. Full article

In this paper, we prepared a new type of iron and nitrogen co-doped porous carbon material (WSC-Fe/N) using a carbonization–activation process with wheat straw as a precursor and FeCl₃ and NH₄Cl as co-doping agents and analyzed the electrochemical properties of the resulting electrode material. Through precise control of the doping elements and carbonization temperature (900 °C), the resulting WSC-Fe/N-900 material exhibits abundant micropores, uniform mesopores, a significant specific surface area (2576.6 m² g⁻¹), an optimal level of iron doping (1.7 wt.%), and excellent graphitization. These characteristics were confirmed through X-ray diffraction and Raman spectroscopy. Additionally, the WSC-Fe/N-900 electrode demonstrated a specific capacitance of 400.5 F g⁻¹ at a current density of 0.5 A g⁻¹, maintaining a high capacitance of 308 F g⁻¹ even at 10 A g⁻¹. The solid-state symmetric supercapacitor in an aqueous electrolyte achieved an energy density of 9.2 Wh kg⁻¹ at a power density of 250 W kg⁻¹ and maintained an energy density of 6.5 Wh kg⁻¹ at a power density of 5000 W kg⁻¹, demonstrating remarkable synergistic energy–power output characteristics. In terms of structural properties, the porous characteristics of WSC-Fe/N-900 not only enhance the specific surface area of the electrode but also improve the diffusion capability of electrolyte ions within the electrode, thereby enhancing capacitance performance. The reliability of the electrode material demonstrated good performance in long-term cycling tests, maintaining a capacitance retention rate of 93% after 10,000 charge–discharge cycles, indicating excellent electrochemical stability. Furthermore, over time, the aging effect of the WSC-Fe/N-900 electrode material is minimal, maintaining high electrochemical performance even after prolonged use, suggesting that this material is suitable for long-term energy storage applications. This study introduces a novel strategy for producing porous carbon materials for supercapacitors, advancing the development of economically efficient and environmentally friendly energy storage solutions. Full article

The hydrogenation of CO₂ to produce formic acid has garnered increasing interest as a means to address climate change and promote the hydrogen economy. This research investigates the nanocasting technique for the synthesis of ordered mesoporous nitrogen-doped carbon (MNC-An). KIT-6 functioned as the silica template, while aniline served as the nitrogen–carbon precursor. The resultant MNC-An exhibits cubic Ia3D geometry, possesses significant mesoporosity, and has a high nitrogen content, which is essential for stabilizing ruthenium single atoms. The catalyst exhibited a specific activity of 252 mmol_FAg_cat⁻¹ following a 2 h reaction at 120 °C. Moreover, the catalyst exhibited exceptional relative activity during five recycling experiments while preserving its catalytic efficacy. The atomically dispersed ruthenium and its Ru³⁺ oxidation state demonstrated perseverance both before and after the treatment. The results indicated that the synthesized catalyst possesses potential for the expedited commercialization of CO₂ hydrogenation to produce formic acid. The elevated carbon yield, along with excellent thermal stability, renders it a viable substrate for attaching and stabilizing atomically dispersed ruthenium catalysts. Full article

The catalytic hydrogenation of the toxic and harmful p-chloronitrobenzene to produce the value-added p-chloroaniline is an essential reaction for the sustainable chemical industry. Nevertheless, ensuring satisfactory control of its chemoselectivity is a great challenge. In this work, a N/S co-doped metal-free carbon catalyst has been fabricated by using cysteine as a source of C, N, and S. The presence of calcium citrate (porogen agent) in the mixture subjected to pyrolysis provided the carbon with porosity, which permitted us to overcome the issues associated with the loss of heteroatoms during an otherwise necessary activation thermal treatment. Full characterization was carried out and the catalytic performance of the metal-free carbon material was tested in the hydrogenation reaction of p-chloronitrobenzene to selectively produce p-chloroaniline. Full selectivity was obtained but conversion was highly dependent on the introduction of S due to the synergetic effect of S and N heteroatoms. The N/S co-doped carbon (CYSCIT) exhibits a mesoporous architecture which favors mass transfer and a higher doping level, with more exposed N and S doping atoms which act as catalytic sites for the hydrogenation of p-chloronitrobenzene, resulting in enhanced catalytic performance when compared to the N-doped carbon obtained from melamine and calcium citrate (MELCIT) used as a reference. Full article

Poly(3,4-ethylenedioxythiophene) (PEDOT) and PEDOT-functionalized carbon nanoparticles (f-CNPs) were synthesized by in situ chemical oxidative polymerization and pyrolysis methods. f-CNP-PEDOT nanocomposites were prepared by varying the concentration of PEDOT from 1 to 20% by weight (i.e., 1, 2.5, 5, 10, and 20 wt%). Several characterization techniques, such as field-emission scanning electron microscopy (FESEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), N₂ Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses, as well as cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS), were applied to investigate the morphology, the crystalline structure, the N₂ adsorption/desorption capability, as well as the electrochemical properties of these new synthesized nanocomposite materials. FESEM analysis showed that these nanocomposites have defined porous structures, and BET surface area analysis showed that the standalone f-CNP exhibited the largest surface area of 801.6 m²/g, whereas the f-CNP-PEDOT with 20 wt% exhibited the smallest surface area of 116 m²/g. The BJH method showed that the nanocomposites were predominantly mesoporous. CV, GCD, and EIS measurements showed that f-CNP functionalized with 5 wt% PEDOT had a higher capacitive performance compared to the individual f-CNPs and PEDOT constituents, exhibiting an extraordinary specific capacitance of 258.7 F/g, at a current density of 0.25 A/g, due to the combined advantage of enhanced electrochemical activity induced by PEDOT doping, and highly developed porosity of f-CNPs. Symmetric aqueous supercapacitor devices were fabricated using the optimized f-CNP-PEDOT doped with 5 wt% of PEDOT as active material, exhibiting a high capacitance of 96.7 F/g at 1.4 V, holding practically their full charge, after 10,000 charge–discharge cycles at 2 A/g, thus providing the highest electrical electrodes performance. Hereafter, this work paves the way for the potential use of f-CNP-PEDOT nanocomposites in the development of high-energy-density supercapacitors. Full article

In recent years, polybenzoxazine aerogels have emerged as promising materials for various applications. However, their full potential has been hindered by the prevalent use of hazardous solvents during the preparation process, which poses significant environmental and safety concerns. In light of this, there is a pressing need to explore alternative methods that can mitigate these issues and propel the practical utilization of polybenzoxazine aerogels. To address this challenge, a novel approach involving the synthesis of heteroatom self-doped mesoporous carbon from polybenzoxazine has been devised. This process utilizes eugenol, stearyl amine, and formaldehyde to create the polybenzoxazine precursor, which is subsequently treated with ethanol as a safer solvent. Notably, the incorporation of boric acid in this method serves a dual purpose: it not only facilitates microstructural regulation but also reinforces the backbone strength of the material through the formation of intermolecular bridged structures between polybenzoxazine chains. Moreover, this approach allows ambient pressure drying, further enhancing its practicability and environmental friendliness. The resultant carbon materials, designated as ESC-N and ESC-G, exhibit distinct characteristics. ESC-N, derived from calcination, possesses a surface area of 289 m² g⁻¹, while ESC-G, derived from the aerogel, boasts a significantly higher surface area of 673 m² g⁻¹. Furthermore, ESC-G features a pore size distribution ranging from 5 to 25 nm, rendering it well suited for electrochemical applications such as supercapacitors. In terms of electrochemical performance, ESC-G demonstrates exceptional potential. With a specific capacitance of 151 F g⁻¹ at a current density of 0.5 A g⁻¹, it exhibits superior energy storage capabilities compared with ESC-N. Additionally, ESC-G displayed a more pronounced rectangular shape in its cyclic voltammogram at a low voltage scanning rate of 20 mV s⁻¹, indicative of enhanced electrochemical reversibility. The impedance spectra of both carbon types corroborated these findings, further validating the superior performance of ESC-G. Furthermore, ESC-G exhibits excellent cycling stability, retaining its electrochemical properties even after 5000 continuous charge–discharge cycles. This robustness underscores its suitability for long-term applications in supercapacitors, reaffirming the viability of heteroatom-doped polybenzoxazine aerogels as a sustainable alternative to traditional carbon materials. Full article

Carbon dots (CDs) have emerged as significant fluorescent nanomaterials due to their bright, stable fluorescence, good biocompatibility, facile synthesis, etc. They are widely used in various scientific and practical applications, particularly in combination with mesoporous, florescent, or magnetic nanomaterials to enhance their properties. Recent research has focused on employing CDs and their composites in drug analysis, drug loading, biological imaging, disease diagnosis, and temperature sensing, with a growing interest in their biological and medical applications. In this study, we synthesized blue-fluorescent S, N-co-doped CDs (cys-CDs) using hydrothermal synthesis with L-cysteine and sodium citrate. These resulting cys-CD particles were approximately 3.8 nm in size and exhibited stable fluorescence with a quantum yield of 0.66. By leveraging the fluorescence quenching of the cys-CDs, we developed a rapid and sensitive method for baicalein detection, achieving high sensitivity in the low micromolar range with a detection limit for baicalein of 33 nM. Our investigation revealed that the fluorescence-quenching mechanism involved static quenching and inner-filter effect components. Overall, cys-CDs proved to be effective for accurate quantitative baicalein detection in real-world samples. Full article

Li–S batteries are positioned as a strong alternative for efficient energy storage due to their high theoretical energy density and their theoretical specific capacity (1675 mA h g⁻¹) compared to current Li-ion batteries; however, their commercialization is affected by the rapid decay of the specific capacity as a consequence of the different species of lithium polysulfides that are generated during the charge–discharge processes. The use of nitrogen-doped mesoporous carbon materials has been shown to have the ability to confer electronic conductivity to sulfur and retain the lithium polysulfide species. However, there are not enough studies to help understand how the type of nitrogen precursor influences the development of specific nitrogen functionalities to favor the retention of lithium polysulfide species. This work seeks to determine the effect of the use of different nitrogen precursors on the structural changes of the mesoporous carbon materials prepared, and thus evaluate the electrochemical behavior of Li–S cells correlating the type of nitrogen functionality generated when the precursor is variated with the charge/discharge capacity developed during the cell operation. For this study, different carbon materials were prepared by the variation of the nitrogen source (melamine, ethylenediamine, and hexadecylamine) to obtain a N-doped mesoporous carbon with different distributions of nitrogen functionalities in its structure. The use of the primary amine ethylenediamine as a nitrogen precursor in the formation of structured carbon materials favored elemental sulfur infiltration into its pores, resulting in the maximum sulfur content within the pores and interacting with the carbonaceous matrix (78.8 wt.%). The carbon material prepared with this precursor resulted in a higher content of N-pyridinic functionality, which, combined with the high content of N-pyrrolic, resulted in the highest specific discharge capacity at 0.1 C after 100 cycles when compared to cells assembled with materials derived from the use of melamine and hexadecylamine precursors. The cell assembled with the electrode formed from ethylenediamine as a nitrogen precursor presented an initial discharge capacity of 918 mA h g⁻¹ with a Coulombic efficiency of ~83.4% at 0.1 C after 100 cycles. Full article

A Fe-Co dual-metal co-doped N containing the carbon composite (FeCo-HNC) was prepared by adjusting the ratio of iron to cobalt as well as the pyrolysis temperature with the assistance of functionalized silica template. Fe₁Co-HNC, which was formed with 1D carbon nanotubes and 2D carbon nanosheets including a rich mesoporous structure, exhibited outstanding oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activities. The ORR half-wave potential is 0.86 V (vs. reversible hydrogen electrode, RHE), and the OER overpotential is 0.76 V at 10 mA cm⁻² with the Fe₁Co-HNC catalyst. It also displayed superior performance in zinc–air batteries. This method provides a promising strategy for the fabrication of efficient transition metal-based carbon catalysts. Full article