Oxygen Co-doped Carbon Research Articles

Enhanced visible light photocatalytic performance of carbon and oxygen co-doped carbon nitride with a three-dimensional structure: Performance and mechanism study

As a cost-effective photocatalyst, carbon nitride (g-C3N4) holds tremendous promise for addressing energy shortages and environmental pollution. However, its application is limited by disadvantages such as low specific surface area and easy recombination of photogenerated electron-hole pairs. This study introduces C and O co-doped g-C3N4 with a three-dimensional (3D) structure achieved through a straightforward one-step calcination process, demonstrating excellent photocatalytic activity of hydrogen production and oxytetracycline degradation, with superoxide radicals as the primary active species. We propose a plausible enhanced mechanism based on systematic characterizations and density functional theory calculations. The 3D structure confers a substantial specific surface area, enhancing both the adsorption area and active sites of catalysts while bolstering structural stability. Co-doping optimizes the band structure and electric conductivity of the catalyst, facilitating rapid migration of photogenerated charges. The synergistic effects of these enhancements significantly elevate the photocatalytic performance. This study presents a convenient and feasible method for the preparation of dual-regulated photocatalysts with outstanding performance.

Driving tetracycline hydrochloride degradation and concomitant hydrogen peroxide photosynthesis in a neutral environment over sulphur and oxygen codoped carbon nitride

The investigation of an artificial photosynthesis system for contaminant treatment and consecutive hydrogen peroxide formation is imperative but challenging, whereas the conversion efficiency is relatively low and far away from the demand for social development. Herein, oxygen and sulphur were collectively introduced into carbon nitride nanosheets (OSCN), together with sufficient edge and basal plane active sites. The as-synthesized sample could achieve a degradation efficiency of 84% for 100 mg/L tetracycline hydrochloride, together with simultaneous hydrogen peroxide production of 366 μmol g−1 h−1 under environmentally friendly neutral conditions. Intriguingly, the addition of tetracycline hydrochloride can accelerate hydrogen peroxide generation, which thus in turn speed up tetracycline hydrochloride degradation. It was revealed that the optimized electronic structure, promoted light-harvesting, and enhanced charge carriers separation capacity are conducive for the synchronous oxygen reduction and contaminant oxidation procedure in large measure. Furthermore, the degradation and hydrogen peroxide generation can be maintained even after 15 cycles, demonstrating the stability of OSCN and its possibility for practical applications. The degradation pathway and in-deep reaction mechanism are carried out accordingly. Additionally, such a synchronously promoted reaction can be extended to some other pollutants, like phenol and 2,4-dichlorophenol. This interesting work provides a novel strategy for pollutants removal and concurrent hydrogen peroxide generation.

One-pot synthesis of highly porous nitrogen and oxygen codoped carbons for solar-driven atmosphere water harvesting

There is significant interest in developing high-performance adsorbents that can harvest water from atmospheric air powered by sunlight. However, The inherent hydrophobicity of porous carbon limits water harvesting capacity. Herein, we report a new class of activated porous carbons (PAK-21) with high water adsorption capacity at moderate to high humidity by solid-phase polymerization of terephthalaldehyde and 2,6-diaminopurine in the presence of KOH under an argon atmosphere at 150 °C for 2 h, and then activated at a high temperature of 700 °C for 1 h. The water harvesting performance surpasses the most common MOFs and porous carbon adsorbents, which benefit from rich surface heterogeneity and highly porous structure. PAK-21 also exhibits fast solar-driven desorption kinetics, ascribing to rapid photothermal responsiveness, hierarchical porosity, and suitable hydrophilicity. Besides, twenty-one adsorption-desorption cycles have been performed to demonstrate its easy regeneration and long-term cyclability. This may pave a new way to modulate the surface functionality and microporous/mesoporous engineering of carbon adsorbents for high-performance solar-driven AWH.

Constructing sulfur and oxygen co-doped carbon nanosheets by tailoring poly tannic acid for fast and stable potassium storage

Carbonaceous material with excellent structural stability and low cost has always been deemed focus of pursuer, nevertheless it showed the sluggish dynamics and large volume expansion as the anode materials for potassium-ion batteries (PIBs). Herein, S, O co-doped ultra-thin carbon nanosheets (S/O-CNS) with enlarged interlayer spacing was synthesized through pyrolysis poly tannic acid with a sulfur-assisted carbonization strategy. Under the unique synthesis process, sulfur acts as a dopant and intercalating agent to acquire few-layer carbon nanosheets with large interlayer spacing (0.42 nm), while oxygen was in-situ doped into the carbon lattice and provides sites for sulfur doping. With the synergistic effects of the co-doping effect and heterostructure, S/O-CNS delivers an excellent reversible capacity of 375.6 mA h g−1 at 0.1 A g−1, an impressive rate performance of 159.9 mA h g−1 even at 10 A g−1 as well as outstanding cycle stability of 198.9 mA h g−1 after 700 cycles at 1.0 A g−1. Kinetics analysis indicates that the capacitance-controlled process plays a dominant role in K+ storage. The results prove that the enlarged interlayer spacing and abundant edge defects accelerate the ion diffusion kinetics. This dual-doping strategy provides a way to design high-performance carbonaceous materials for PIBs.

All-Carbon Solution-Gated Transistor with Low Operating Voltages for Highly Selective and Stable Dopamine Sensing.

The diversity of carbon materials makes it possible to prepare all-carbon electronic devices requiring components with different properties and functions. In this work, we fabricate an all-carbon solution-gated transistor (AC-SGT) based dopamine (DA) sensor with Nafion coated nitrogen and oxygen co-doped carbon yarn (Nafion/NOCY) as the gate electrode and graphene as the channel. The carbon materials in AC-SGT render the usage of a variety of strategies to improve its electrochemical sensing capability including the modification of the gate electrode and the modulation of the operating voltage. With a low gate-source voltage of 0.02 V as well as a low drain-source voltage of 0.05 V, AC-SGT manifests the outstanding DA sensing performances in terms of sensitivity, selectivity, limit of detection (3 nM, S/N > 3), linear range (3 nM to 300 μM), long-term stability (over 30 days), and preconditioning time (60 s). Furthermore, a smartphone controlled portable sensing system integrated with AC-SGT is fabricated herein, which shows the excellent in vitro sensing capability of DA in urine, proving the potential of all-carbon transistors in smart wearable biosensors.

Synergetic contribution of carbon and oxygen co-doped carbon nitride nanosheets as metal-free photocatalysts for wastewater purification

Graphitic carbon nitride (g-C3N4) has attracted much scientific interest for photocatalysis, but the low photocatalytic efficiency seriously restricted the further practical application. In this work, C/O co-doped g-C3N4 photocatalyst (C/O–CN) was synthesized by a simple calcination method using urea and proline as the precursors. Experimental results disclosed that the co-doping of C/O into CN framework can induce the synergetic regulating effect, which not only improved the light absorption and narrow band gap, but also promoted the charge transfer. The C/O–CN photocatalysts showed superior photocatalytic performance in degradation rhodamine B (RhB) compared to the pristine CN. Moreover, the optimized degradation RhB parameters were also discussed in depth. This synergetic effect opens a new perspective in design low-cost and efficient bioelement co-doped CN based metal free photocatalyst in environmental purification and energy conversion.

Phosphorus and oxygen co-doped carbon particles based on almond shells with hydrothermal and microwave irradiation process for adsorption of lead (II) and cadmium (II).

In this study, the production of activated carbon based on almond shells by microwave heating with KOH activation and then the modification of activated carbon with phosphorus and oxygen as a result of hydrothermal heating with phosphoric acid were carried out to increase the Cd(II) and Pb(II) adsorption efficiency. The resulting materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric/differential thermal analyzer (TG-DTA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and nitrogen adsorption. Adsorption performance, kinetics and thermodynamics of phosphorus, and oxygen-doped activated carbons were evaluated. The results showed that the adsorption of both Cd(II) and Pb(II) on phosphorus and oxygen-doped activated carbons obeyed the Langmuir isotherm and pseudo-second-order kinetics. The adsorption capacity values (Qm) obtained from the Langmuir isotherm for Cd(II) and Pb(II) adsorption were 185.18mg/g and 54.64mg/g, respectively. At the same time, the adsorption mechanism of Pb(II) and Cd(II) on the respective adsorbents was evaluated. As a result of phosphorus and oxygen atoms, Lewis base sites on carbon atoms and Lewis acid sites on phosphorus atoms are likely to form on the surface. These Lewis base sites can act as important active sites in adsorption reactions, especially of positively charged Pb(II) and Cd(II) ions.

Design and Architecture of P-O Co-Doped Porous g-C3N4 by Supramolecular Self-Assembly for Enhanced Hydrogen Evolution

A novel phosphorus and oxygen co-doped graphitic carbon nitride (sheetP-O-CNSSA) photocatalyst was successfully synthesized and applied for H2 evolution under visible light. In the synthesis process of sheetP-O-CNSSA, the supramolecular complex was developed by the self-assembly and copolymerization reaction among melamine, cyanuric acid (CA) and trithiocyanuric acid (TCA) to act as g-C3N4 precursors, while (NH4)2HPO4 was applied as P and O precursors for element doping. The chemical structures, morphologies, and optical properties of the sheetP-O-CNSSA were characterized by a series of measurements, i.e., XRD, FT-IR, SEM, TEM, UV-vis DRS, and PL. The results suggested that the introduction of P and O elements could enhance the separation and migration efficiency of photogenerated electrons and holes in the energy band of g-C3N4. The photocatalytic tests over Erythrosin B (EB) sensitized sheetP-O-CNSSA indicated that the hydrogen evolution was greatly enhanced compared with other catalysts and non-sensitized sheetP-O-CNSSA under visible light irradiation. Finally, a possible dye-sensitized photocatalysis mechanism was also proposed on the basis of the as-obtained results.

Nitrogen and oxygen co-doped carbon micro-foams derived from gelatin as high-performance cathode materials of Zn-ion capacitors

Nitrogen and oxygen co-doped micro-foam like mesoporous carbons are prepared from gelatin, an abundant hydrolyzed product of animal collagen with high carbon content and fruitful heteroatoms. Benefiting from the swelled structure of gelatin after pre‑carbonization at 300 °C, the following moderate chemical activation with KOH results in highly mesoporous carbons with specific surface area over 3000 m2 g−1 and total pore volume larger than 1.96 cm3 g−1 while preserving the micro-foam structure. As cathode materials of zinc ion capacitors (ZICs), the carbon micro-foams display very encouraging energy storage performance in both organic and aqueous electrolytes. A high energy density of 90 Wh kg−1 is obtained at a power density of 445 W kg−1 in 1 M Zn(CF3SO3)2/DMF (N, N-dimethylformamide) electrolyte, whereas in 1 M ZnSO4 aqueous electrolyte the ZIC exhibits much better rate capability (54 Wh kg−1 at 14650 W kg−1) possibly due to the better wettability and higher ionic conductivity. These excellent electrochemical properties suggest that the N and O co-doped mesoporous carbon micro-foams derived from gelatin can be potential cathode materials of high-performance Zn-ion capacitors.

Design of copper oxide and oxygen codoped graphitic carbon nitride activator for efficient radical and nonradical activation of peroxymonosulfate

Rational regulation of stable graphitic carbon nitride (CN) for superior peroxymonosulfate (PMS) activation is important in the catalytic degradation of water contaminants. In this work, the copper oxide and oxygen co-doped graphitic carbon nitride (CuO/O-CN) was prepared via one-step synthesis and applied in activating PMS for oxytetracycline (OTC) degradation, displaying superior catalytic performance. Systematic characterization and theoretical calculations indicated that the synergistic effect between the oxygen site of CN and CuO can modulate the electronic structure of the whole composite further facilitating the formation of non-radical 1O2 and various reactive radicals. Results of the influencing factor experiments revealed that CuO/O-CN has a strong resistance to the environmental impact. The degradation efficiency of OTC in the real water environment even exceeded that in the deionized water. After four successive runs of the optimal catalyst, the OTC removal rate was still as high as 91.3%. This work developed a high-efficiency PMS activator to remove refractory pollutants via both radical pathway and non-radical pathway, which showed a promising potential in the treatment of wastewaters.

Nitrogen and Oxygen Co-doped Porous Carbon Fabric for Efficient Removal of Formaldehyde

Nitrogen and Oxygen Co-doped Porous Carbon Fabric for Efficient Removal of Formaldehyde

Facile synthesis of sulfur and oxygen co-doped graphitic carbon nitride quantum dots for on-off detection of Cu2+ in real samples and living cells

A fluorescent sulfur and oxygen co-doped graphitic carbon nitride quantum dots (S,O-CNQDs) were prepared from ethylenediaminetetraacetic acid disodium salt dihydrate and thiourea as the carbon and sulfur sources. The morphology and surface functional groups of S,O-CNQDs were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The fluorescence of S,O-CNQDs could be quenched efficiently by Cu2+ under the optimum conditions. The S,O-CNQDs could function as an excellent fluorescent probe for Cu2+ detection with a wide linear range of 0.50–15 μM and a low detection limit of 0.58 nM. In addition, this fluorescent probe was employed for monitoring Cu2+ in samples of tap water, lake water, human serum and urine with good recoveries from 99.0% to 110.0%. Moreover, the S,O-CNQDs with high cell penetration and low cytotoxicity were utilized for Cu2+ detection in living cells. Owing to the excellent properties of S,O-CNQDs, the as-prepared S,O-CNQDs can be a potential candidate for biological 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.

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.

Nickel-rich NiCeLaFeCo medium-entropy alloy nanoparticles on oxygen and nitrogen co-doped carbon supports for hydrogen production from toluene cracking

Multi-metallic nanoparticles (MMNPs) attract people’s attention due to their great potential in the application of energy storage, medicine, and catalysis. In this study, a simple in situ reduction method was developed to synthesize the NiCeLaFeCo and NiCeLaFeCu medium-entropy alloy (MEA) nanoparticles on nitrogen and oxygen co-doped carbon supports, with guanine and transition metal nitrates as the precursors. The prepared face-centered cubic (FCC) NiCeLaFeCo MEA nanoparticles have small particle sizes (average 21.1 nm) and medium mixing entropy (1.31 R). To extend the application of MEA nanoparticles, we have conducted a toluene cracking test regarding toluene conversion and hydrogen generation. The catalyst loaded with nickel-rich (~55.26%) MEA nanoparticles presented a high catalytic performance (over 80% conversion and 7293 ppm hydrogen generation) at 500 °C upon 2 h time-on-stream, and better catalytic performance (99% conversion and 78960 ppm hydrogen generation) at 400 °C with steam reforming. This study has provided a simple and convenient way to synthesize the functionalized carbon-based multi-metallic nanoparticles, and showed their excellent catalytic performance in the toluene cracking and hydrogen generation.

Enhanced light harvesting and charge separation of carbon and oxygen co-doped carbon nitride as excellent photocatalyst for hydrogen evolution reaction

Solar-driven water splitting has been regarded as a promising strategy for renewable hydrogen production. Among many semiconductor photocatalysts, graphitic carbon nitride (g-C3N4) has received tremendous attention due to its two-dimensional structure, appropriate band gap and decent photocatalytic activity. However, it suffers severe charge recombination problems, affecting its practical performance. In this work, we demonstrated that dual heteroatoms (C and O) doped g-C3N4 can exhibit about 3 times higher catalytic performance for hydrogen evolution than that of the normal g-C3N4 with a hydrogen evolution rate reaching 2595.4 umol g−1h−1 and an apparent quantum efficiency at 420 nm of 16.6%. The heteroatoms (C and O) doped g-C3N4 photocatalyst also exhibited superior removal performance when removing Rhodamine B (RhB) . X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (ssNMR) and X-ray absorption near-edge structure (XANES) spectroscopy reveal that the carbon and oxygen dopants replace the sp2 nitrogen and bridging N atom, respectively. DFT calculations demonstrate the codoping of carbon and oxygen- induced the generation of mid-gap state, leading to the improvement of light harvesting and charge separation.

Phosphorescence Tuning of Fluorine, Oxygen-Codoped Carbon Dots by Substrate Engineering

Phosphorescence Tuning of Fluorine, Oxygen-Codoped Carbon Dots by Substrate Engineering

Rational design to manganese and oxygen co-doped polymeric carbon nitride for efficient nonradical activation of peroxymonosulfate and the mechanism insight

Polymeric carbon nitride (PCN) based materials have emerged as promising catalysts to activate peroxymonosulfate (PMS) for organic pollutant removal. In this work, the Mn and O co-doped polymeric carbon nitride (Mn/O-PCN) was synthesized via simple calcination and activated PMS for enrofloxacin (ENR) removal. The obtained Mn/O-PCN + PMS system exhibited excellent reactivity for ENR degradation. The Mn and O co-dopants could modulate the electronic structure of PCN. ENR can be oxidized by electrons transferring and 1O2 on the surface of Mn/O-PCN + PMS complex via a non-radical way. A positive correlation was observed between ENR oxidation rates and the Mn content. Effects of pH, PMS concentration, and different ions on the degradation of ENR have also been studied. Cycling experiments showed that Mn/O-PCN materials have good reusability. Our study reported an effective PMS activator for organic pollutants removal and revealed the mechanism of active sites in modified PCN during non-radical PMS activation.

Design and structure of nitrogen and oxygen co-doped carbon spheres with wrinkled nanocages as active material for supercapacitor application

Nitrogen/oxygen co-doped carbon spheres with wrinkled nanocages (NOCN) were successfully synthesized using dendritic fibrous nanosilica (DFNS) as sacrificial solid template, glucose as a carbon source, and melamine as the nitrogen source. The obtained carbon nanocages (NOCN-850-3) exhibit human brain-like winkle shape, high specific surface area (813 m2 g−1), high nitrogen (16.24 at%) and oxygen contents (5.36 at%). In addition, the obtained carbon presents good specific capacitance of 311.1 F g−1 at a current density of 0.5 A g−1 in 6 M KOH and remarkable rate performance (118.1 F g−1 at a current density of 30 A g−1) and cycle stability (97.6% retention after 10,000 charge–discharge performance cycles at 10 A g−1). Meanwhile, the NOCN-850-3-based coin-type symmetric supercapacitor exhibits a maximum energy density of 12. 3 W h kg−1 at a power density of 175 W kg−1 and also a relatively low resistance in 6 M KOH aqueous electrolyte. Thus, the unique structure and nitrogen/oxygen co-doping characteristic endue the electrode material a potential application in supercapacitors.

Synergistic effect of PMS activation by Fe0@Fe3O4 anchored on N, S, O co-doped carbon composite for degradation of sulfamethoxazole

High efficient activator is highly desired in the field of persulfate-based advanced oxidation process. In comparison with the previous studies, this study adopted nitrogen, sulfur and oxygen co-doped carbon material to support Fe0 encapsulate in Fe3O4 to prepare iron-based modified carbon composite (Fe0@Fe3O4-MC) by a facile two-step pyrolysis. Fe0@Fe3O4-MC was then used for degradation of sulfamethoxazole. The results showed that Fe0@Fe3O4-MC had superior catalytic activity for PMS activation due to the synergistic effect of iron-based compound and modified carbon. In the presence of 0.1 g/L of Fe0@Fe3O4-MC, SMX (0.04 mM) could be completely degraded within 120 min at pH 3.4 and 3 mM of PMS. The SMX degradation followed pseudo first-order kinetic model, with the rate constant of 0.12 min−1, and the mineralization of SMX achieved 48.4%. Sulfate radicals dominated in the SMX degradation. In addition to Fe0 and Fe3O4, carbon defects, graphitic N, sulfur and FeN4 also contributed to PMS activation. Fe0 oxidation was the rate-limiting step for PMS activation. Dissolved oxygen made a minor contribution to Fe0 oxidation. The intermediate products of SMX degradation were identified, and two pathways of SMX degradation were proposed. The influencing factors on SMX degradation were studied, including pH, temperature, PMS concentration, Fe0@Fe3O4-MC dosage, chloridion, carbonate and humic acids, and the influencing mechanism was discussed. This study could provide an efficient PMS activator for the degradation of emerging organic pollutants in water and wastewater.