Graphene-like Carbon Nanosheets Research Articles

Natural Kapok fiber-derived two-dimensional carbonized sheets as sustainable electrode material

Natural biomass-derived carbon nanostructures have attracted research interest because of their unique surface and electrochemical properties. The present study embodied the carbonized micro-nano sheets derived from the low-cost natural source Kapok silk fiber. The material was obtained via a facile thermal pyrolysis process. Diffraction analysis showed a broad graphene structure-like peak, indicating the formation of graphene-like carbon nanosheets. Field emission scanning electron microscope (FESEM) and transmission electron microscopic (TEM) images confirmed the presence of fragmented carbon sheets, some of which were folded to form a tube-like structure. Raman study showed the presence of D and G band with the Id/Ig ratio of 0.96 which indicated the formation of few-layered carbon nanosheets. Furthermore, the electrochemical performance was evaluated for lithium-ion battery as well as supercapacitor. A specific capacity of 465 mAh.g-1 at 0.1 C rate for Li-ion battery and a specific capacitance of 473.61 F.g-1 for supercapacitor have been obtained with the capacitance retention of 95 %. This study provides insights into a strategy for the sustainable production and utilization of natural fiber-based carbon in energy storage systems.

Flash Joule Heating Synthesis of Layer-Stacked Vanadium Oxide/Graphene Hybrids within Seconds for High-Performance Aqueous Zinc-Ion Batteries.

Vanadium oxides have been regarded as highly promising cathodes for aqueous zinc-ion batteries (ZIBs). However, obtaining high-performance vanadium oxide-based cathodes suitable for industrial application remains a significant challenge due to the need for cost-effective, straightforward, and efficient preparation methods. Herein, we present a facile and rapid synthesis of a composite cathode, consisting of layer-stacked VO2/V2O5 and graphene-like carbon nanosheets, in just 2.5 s by treating the commercial V2O5 powder via a flash Joule heating strategy. When employed as the cathode for ZIBs, the resulting composite delivers a comparable rate capacity of 459 mA h g-1 at 0.2 A g-1 and remarkable cycle stabilities of 355.5 mA h g-1 after 2500 cycles at 1.0 A g-1 and 169.5 mA h g-1 after 10,000 cycles at 10 A g-1, respectively. Further electrochemical analysis reveals that the impressive performance is attributed to the accelerated charge transfer and the alleviated structure degradation, facilitated by the abundant sites and a built-in electric field of the layer-stacked VO2/V2O5 heterostructure, as well as the excellent conductivity of graphene-like carbon nanosheets. This work introduces a unique approach for ultrafast and low-cost fabrication of high-performance vanadium oxide-based composite cathodes toward efficient ZIBs.

Fluorine atoms incorporation strengthens the strong metal-support interaction of PtNi@NFGC for enhanced methanol oxidation reaction performance under alkaline media

The regulatory mechanism of strong metal-support interaction (SMSI) is of great significance in improving the electrocatalytic performance for supported electrocatalysts. Here, PtNi alloy nanoparticles were deposited on N, F-codoped graphene-like carbon nanosheets (PtNi@NFGC) to construct a highly active interface for efficient methanol oxidation reaction (MOR), which solves the problems of high cost, poor activity and easy aggregation of Pt-based catalysts. Due to the high electrophilicity, F atoms doping into the carbon lattice can not only manipulate the electron structure and the state of the carbon skeleton, but also further trigger the stronger charge transfer between metal atoms and carbon support. Compared with single-doped PtNi@NGC, N, F-codoped PtNi@NFGC possesses a lower onset potential and methanol oxidation potential, higher methanol oxidation current and stronger CO tolerance. The results of the partial density of state (PDOS) simulation display that N, F-codoping promotes the electron transfer from Pt atoms to NFGC support, and leads to the d-band center shift upward, thus strengthening the oxidation degree of Pt active sites and increasing the composition of high-valent Ptx+. In-situ Raman analysis and density functional theory (DFT) results expound that F atoms embedding observably enhances the adsorption energy of Pt active centers to *OH intermediates, which not only significantly improves MOR catalytic activity, but also achieves efficient methanol dehydrogenation and alleviates CO poisoning. This customization of metal-support interface interaction by heteroatom doping strategy opens up opportunities for designing efficient supported catalysts.

Guanine-derived core-shell FeCo alloy confined in graphene-like N-doped carbon as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries

Maximization the synergistic effect of each component in transition metal-carbon complexes is expected to improve the bifunctional oxygen electrocatalysis for rechargeable Zn-air batteries but is still challenging. Herein, nucleobase guanine is employed as a supramolecular precursor to generate the core (FeCo alloy)-shell (carbon) structure embedded in ultrathin graphene-like nitrogen-doped carbon nanosheets (FeCo@NCNSs) via a confinement pyrolysis strategy. Thanks to the generated core-shell structure and bimetallic synergistic effect, the as-prepared FeCo@NCNSs exhibits excellent electrochemical performance in both oxygen reduction reaction and oxygen evolution reaction. As a result, when served as the bifunctional air electrode for a practical Zn-air battery, FeCo@NCNSs exhibits a higher open-circuit voltage (1.553 V) and peak power density (197.30 mW cm−2), as well as the greatly improved long-term cyclic stability compared to the noble metal benchmarks. This work provides a promising approach to integrate various active sites for bifunctional oxygen electrocatalysis and inspires the exploration of simple but efficient electrocatalysts for energy storage and conversion.

Preparation and Lithium-Ion Capacitance Performance of Nitrogen and Sulfur Co-Doped Carbon Nanosheets with Limited Space via the Vermiculite Template Method.

Nitrogen and sulfur co-doped graphene-like carbon nanosheets (CNSs) with a two-dimensional structure are prepared by using methylene blue as a carbon source and expanded vermiculite as a template. After static negative pressure adsorption, high-temperature calcination, and etching in a vacuum oven, they are embedded in the limited space of the vermiculite template. The addition of an appropriate number of mixed elements can improve the performance of a battery. Via scanning electron microscopy, it is found that the prepared nitrogen-sulfur-co-doped carbon nanosheets exhibit a thin yarn shape. The XPS results show that there are four elements of C, N, O, and S in the carbon materials (CNS-600, CNS-700, CNS-800, CNS-900) prepared at different temperatures, and the N atom content shows a gradually decreasing trend. It is mainly doped into a graphene-like network in four ways (graphite nitrogen, pyridine nitrogen, pyrrole nitrogen, and pyridine nitrogen oxide), while the S element shows an increasing trend, mainly in the form of thiophene S and sulfur, which is covalently linked to oxygen. The results show that CNS-700 has a discharge-specific capacity of 460 mAh/g at a current density of 0.1 A/g, and it can still maintain a specific capacity of 200 mAh/g at a current density of 2 A/g. The assembled lithium-ion capacitor has excellent energy density and power density, with a maximum power density of 20,000 W/kg.

N and P co-doped graphene-like carbon nanosheet as metal-free catalyst for selective oxidation of methacrolein to methacrylic acid: High methacrylic acid selectivity

Methacrylic acid (MAA) is an important chemical intermediate. In this study, a kind of nitrogen-phosphorus co-doped graphene-like carbon nanosheet catalysts have been prepared by co-pyrolysis of starch and (NH4)2HPO4, which have high specific surface area (1057.55 m2g−1) and excellent catalytic performance (35% of MAL conversion and 90% of MAA selectivity) for the selective oxidation of methacrolein to methacrylic acid. The graphite nitrogen provides new active sites for adsorption and activation of O2 which can accelerate the reaction. P in carbon skeleton can enrich the electron on the surface of carbon catalyst and turn the electrophilic groups to nucleophilic groups which can increase the MAA selectivity. This study provides a convenient and fast method to prepare efficient nitrogen and phosphorus co-doped carbon catalysts for the selective oxidation of methacrolein to methacrylic acid.

From grape bagasse to graphene-like porous carbon nanosheets for CO2 capture.

Graphene-based materials have increasingly attracted attention in recent years. It is a material is recognized worldwide due to its numerous applications in several sectors. However, graphene production involves several challenges: scalability, high costs, and high-quality production. This study synthesized graphene-like porous carbon nanosheets (GPCNs) through a thermochemical process under a nitrogen atmosphere using grape bagasse as a precursor. Three temperatures (700, 800, and 900 ºC) of the pyrolysis process were studied. Chemical graphitization and activation were used to form high-specific surface area materials: FeCl3.6H2O(aq) and ZnCl2(s) in a simultaneous activation-graphitization (SAG) method. The materials obtained (GPCN700, GPCN800, and GPCN900) were compared to previously produced chars (C700, C800, and C900). A high specific surface area and total pore volume were obtained for GPCN materials, and GPCN900 presented the highest values: 1062.7 m2g-1 and 0.635 cm3g-1, respectively. The GPCN and char materials were classified as mesoporous and applied as adsorbents for CO2(g). The GPCN800 presented the best CO2(g) adsorbent, with a CO2(g) adsorption capacity of 168.71mgg-1.

Densified graphene-like carbon nanosheets with enriched heteroatoms enabling superior gravimetric and volumetric potassium storage capacities

Constructing carbon electrodes with abundant heteroatoms and appropriate graphitic interlayer spacing remains a major challenge for achieving high gravimetric and volumetric potassium storage capacities with fast kinetics. Herein, we constructed 3D graphene-like N, F dual-doped carbon sheets induced by Ni template (N, F-CNS-Ni) with dense structure and rich active sites, providing a promising approach to address the facing obstacles. Highly reversible K-ion insertion/extraction is realized in the graphitic carbon structure, and K-adsorption capability is enhanced by introducing N/F heteroatoms. As a result, the N, F-CNS-Ni electrode exhibits ultrahigh gravimetric and volumetric capacities of 404.5 mA h g−1 and 281.3 mA h cm−3 at 0.05 A/g, respectively, and a superb capacity of 259.3 mA h g−1 with a capacity retention ratio of 90 % even after 600 cycles at 5 A/g. This work presents a simple Ni-based template method to prepare graphene-like carbon nanosheets with high packing density and rich heteroatoms, and offers mechanism insight for achieving superior K-ion storage.

Manganese oxide nanocrystals embedded porous Graphene-like network for electrosynthesis of H2O2 and construction of Self-powered aptasensor

To improve the selectivity and production rate of the H2O2 electrosynthesis, an electrocatalyst was established based on ultrathin graphene-like mesoporous carbon nanosheets embedded with ultra-small manganese oxide (MnOx) nanocrystals (denoted as MnOx@C). A polymer-manganese-metal–organic framework (polyMn-MOF) was used as the precursor for the preparation of the series of MnOx@C hybrid by calcining at different temperature (600, 700, and 800 °C) under nitrogen atomsphere. Density functional theory simulation revealed that MnOx@C-700 obtained by pyrolyzing polyMn-MOF at 700 °C exhibited the optimization adsorption energy of *OOH, thus showing a high H2O2 selectivity of 96.5 % and large limited oxygen reduction current of 2.3 mA cm−2. Meanwhile a high mass activity of 35.56 A g−1 (at 0.4 V vs the reversible hydrogen electrode) and high durability over 10 h were attained for the MnOx@C-700 catalyst. Moreover, the MnOx@C-700-assembled Zn-air battery (ZAB) showed a large open-circuit voltage of 1.34 V and a remarkable peak power density of 2.22 mW cm−2. The constructed ZAB-driven self-powered aptasensor demonstrated a wide linear range of 0.1 pg mL−1–100 ng mL−1 and an ultralow detection limit of 0.08 pg mL−1 toward diethylstilbestrol. This work provided new insights onto the H2O2 electrosynthesis and detection of hazards using the self-powered biosensing strategy.

Boosting Li-O2 Battery Performance via Coupling of P-N Site-Rich N, P Co-Doped Graphene-Like Carbon Nanosheets with Nano-CePO4.

Development of efficient and robust cathode catalysts is critical for the commercialization of Li-O2 batteries (LOBs). Herein, a well-designed CePO4 @N-P-CNSs cathode catalyst for LOBs via coupling P-N site-rich N, P co-doped graphene-like carbon nanosheets (N-P-CNSs) with nano-CePO4 via a novel "in situ derivation" coupling strategy by in situ transforming the P atoms of P-C sites in N-P-CNSs to CePO4 is reported. The CePO4 @N-P-CNSs exhibit superior bifunctional ORR/OER activity relative to commercial Pt/C-RuO2 with an overall overpotential of 0.64V (vs RHE). Moreover, the LOB with CePO4 @N-P-CNSs as the cathode catalyst delivers a low charge overpotential of 0.67V (vs Li/Li+ ), high discharge capacity of 29774 mAh g-1 at 100mA g-1 and long cycling stability of 415 cycles, respectively. The remarkably enhanced LOB performance is attributable to the in situ derived CePO4 nanoparticles and the P-N sites in N-P-CNSs, which facilitate increased bifunctional ORR/OER activity, promote the rapid and effective decomposition of Li2 O2 and inhibit the formation of Li2 CO3 . This work may provide new inspiration for designing efficient, durable, and cost-effective cathode catalysts for LOBs.

Hierarchical porous nitrogen-doped carbon nanosheets derived from zinc-based bioMOF as flexible supercapacitor electrode

We propose an efficient and flexible supercapacitor electrode material based on hierarchically structured nitrogen-doped graphene-like carbon nanosheets (H-NCNs) with accordion-like shape. H-NCNs were obtained by pyrolyzing zinc-based biometal–organic frameworks (Zn-bioMOFs) and using urea as nitrogen source at high temperature (800 °C) under nitrogen atmosphere, and Zn-bioMOFs were synthesized using biomass molecules, i.e., curcumin. Inheriting from the features of Zn-bioMOF, H-NCNs showed hierarchical structures and unique accordion-like morphology. By changing the urea dosage, the nitrogen-doping degree and porosity of H-NCNs were regulated, optimizing the supercapacitive performance. H-NCNs-8 prepared with Zn-bioMOF/urea mass ratio of 1:8 exhibited high specific capacitance and superior rate capability (293 F g−1 at 0.25 A g−1 and 188 F g−1 at 50 A g−1). The H-NCNs-assembled symmetric supercapacitor offered long cycle life of over 40,000 cycles at 2 A/g and high energy density of 17.6 Wh kg−1 at 250 W kg−1, outperforming most carbon nanomaterial-related ones. Accordingly, the proposed flexible interdigital solid microsupercapacitor demonstrated high areal capacitance, high areal energy densities, and long cycle stability. The present work can provide promising application prospects of MOFs in the field of supercapacitors and flexible electronics.

In Situ Exfoliated Graphene-Like Carbon Nanosheets Strongly Coupled with the Biochar Tube as the Cathode for an Application-Ready Zn-Air Battery

In Situ Exfoliated Graphene-Like Carbon Nanosheets Strongly Coupled with the Biochar Tube as the Cathode for an Application-Ready Zn-Air Battery

3D graphene-like oxygen and sulfur-doped porous carbon nanosheets with multilevel ion channels for high-performance aqueous Zn-ion storage

Zinc-ion hybrid capacitors (ZIHC) demonstrate impressive charge-storage performance and intrinsic safety due to the inherited superiorities of aqueous rechargeable batteries and supercapacitors. However, the promotion of electrochemical performance is usually hindered by the cathode materials that fail to hold high energy density and rate capability of ZIHC. The optimization of porous carbon cathodes into a hierarchical structure is an efficient strategy to break the bottlenecks of ZIHC. Herein, a metal oxide space-confined strategy is proposed to build 3D graphene-like porous carbon nanosheets (3DPC) with doping of O and S heteroatoms by using low-cost aromatic hydrocarbons as precursors. It is found that the obtained 3DPC consists of micro-, mseo- and macropores and further delivers a high specific surface area of 2813 m2 g−1 with a total pore volume of 1.82 cm3 g−1. Specifically, such a well-defined hierarchical porosity of 3DPC coupled with rich O and S heteroatoms enables sufficient multilevel ion transport channels and large accessible surface sites to capture the Zn2+ ions. As a proof of concept demonstration, the assembled aqueous ZIHC by employing the 3DPC cathode exhibits a desirable capacity of 194 mAh g−1 at 0.5 A g−1 with a superior rate capability of 53% at 30 A g−1 and excellent cycling stability of over 88% after 15000 cycles. Moreover, the remarkable electrochemical performance of the 3DPC cathode can be well-preserved in the case of a quasi-solid-state ZIHC device under various harsh bent states, highlighting the promising application in flexible and wearable energy storage.

Eutectic salt induced self-activation technique for porous graphene-like carbon nanosheets as the high-capacity cathodes for Zn-ion hybrid supercapacitors

• Graphene-like carbon nanosheets were obtained in different eutectic salts. • In-situ formed Na 2 CO 3 can serve as a chemical activation agent. • The roles of eutectic salt have been revealed. • The carbon has a surface area of 1739.5 m 2 /g with hierarchical pores. • The carbon nanosheets achieved high specific capacity of 169.1 mAh g −1 . The exploration of a non-corrosive and sustainable strategy to produce thin graphene-like porous carbon nanosheets with large specific surface area for electrochemical energy storage applications is highly desired yet a huge challenge. Herein, we report a eutectic salt induced self-activation process for the synthesis of a serials of porous carbon nanosheets with well-controlled microstructures just by simply changing the type of eutectic salt. The experiment results illustrated that the in-situ formed Na 2 CO 3 , which is usually “inert” when serves as a chemical activation reagent at relatively low temperature, display a significant enhanced chemical activation in eutectic salt medium. Specifically, thin graphene-like porous carbon nanosheets with a large specific surface of 1739.5 m 2 /g can be obtained in CsCl-NaCl eutectic salt. When acts as a cathode for Zn-ion hybrid supercapacitors (ZSCs), a high specific capacity of 169.1 mAh/g (at 0.1 A/g), large specific energy of 62.24 W h kg −1 (at an ultrahigh specific power of 16 kW g −1 ) and cyclic stability of 91.7 % after 10,000 cycles. In addition, a quasi-solid-state ZSC device, which can freely realize series to increase the working voltage, demonstrated its hold a potential for practical application. This strategy combines the advantages of the in-situ chemical activation with the advantages of the eutectic salt medium, which offers an alternative way for the producing of various functional nanocarbons for a variety of applications including electrochemical energy storage.

Electric field-assisted in situ fabrication of carbon/zirconia nanocomposites with tunable conductivity for electromagnetic interference shielding applications

Carbon/ceramic nanocomposites have been considered as ideal candidates for electromagnetic interference shielding (EMI) applications in harsh environments. However, the conventional fabrication methods of carbon/ceramic composites are often complicated, costly and time-consuming. Herein, by applying a DC electric field during hot pressing sintering, we realized the direct growth of graphene-like carbon nanosheets (GCNs) in zirconia ceramics during sintering, achieving in situ fabrication of GCNs/zirconia nanocomposites with both high EMI shielding effectiveness (>40 dB) and mechanical strength (>1000 MPa) in one step. In particular, we found that applying a DC electric field could significantly enhance the carburization during sintering, and GCNs are in situ formed at zirconia grain boundaries. When the initial electric field is constant, the amount of in situ formed GCNs could be controlled by simply adjusting the current density, resulting in the tunable electrical conductivity. These findings will provide new opportunities for both experimental and theoretical studies on carbon/ceramic EMI shielding materials and the DC electric field-assisted sintering technique.

The nitrogen-doped graphene-like carbon nanosheets: Confined construction and oxygen-limited oxidation for higher removal efficiency toward organic contaminants

Due to the excellent properties, including large specific surface area, stable structure, and strong adsorbability, mesoporous carbon material has captured a lot of attention and applied to various fields. Here, we proposed a facile approach to synthesize nitrogen-doped graphene-like carbon (NGLC) nanosheets and investigated the performance in wastewater decontamination. In this work, NGLC nanosheets were obtained via the combination of confined synthesis and low-temperature calcination in oxygen-limited condition. Such NGLC nanosheets were composed of several carbon layers with porous structure, which provided a large specific surface area (421.85 m2 g−1). Meanwhile, the NGLC was endowed with abundant active sites, including oxygen-contained groups and nitrogen species, via low-temperature calcination in oxygen-limited conditions. These properties allow the NGLC to be an excellent adsorbent for organic pollution treatment. The maximum adsorption capacities toward cationic dyes, the rhodamine B (RhB) and methylene blue (MB), reached as high as 1272.74 mg g−1 and 679.55 mg g−1, respectively, indicating the promising potential for the cationic contaminants treatment. The excellent reusability and wide pH suitability (2–10) were observed by batch adsorption experiments. The kinetic adsorption test showed that 98.97% of RhB could be adsorbed by NGLC-450 after 150 min contact time at 25 °C, while the RhB removal efficiencies from bulk polydopamine derived carbon material (denoted as PDA carbon) and NGLC-450-Ar (generated at argon atmosphere) were only 17.56% and 62.03%, respectively. The significant difference in adsorption performance implied the importance of confined synthesis with template-assistance and oxygen-limited oxidation. The adsorption process involved the pore filling & adsorption, electrostatic interaction, and π-π interaction, as well as the hydrogen bonding, which was demonstrated by experiment and Fourier transform infrared (FT-IR) & X-ray photoelectron spectroscopy (XPS) analysis.

Oxygen vacancies-enriched Cu/Co bimetallic oxides catalysts for high-efficiency peroxymonosulfate activation to degrade TC: Insight into the increase of Cu+ triggered by Co doping

Bimetallic CuCo-doped graphene-like carbon nanosheets (CuCo@GCNs) were synthesized via a facile and efficient process using agarose as carbon templates to activate peroxymonosulfate (PMS) for tetracycline (TC) degradation. In this study, CuCo@GCNs/PMS system exhibited excellent TC removal efficiency (0.182 min−1), which was unaffected by various water matrices and applicable to a wide pH range (3.44–8.44). Radicals (SO4•−, •OH, and O2•−) and non-radical (1O2) pathways collectively contributed to catalytic TC oxidation based on quenching experiments and electron paramagnetic resonance (EPR) analysis. Density functional theory (DFT) calculations revealed that the mechanism of PMS molecules activated on the surface of CuCo@GCNs, in which CoO provided more catalytic sites while Cu2O further enhanced electron transfer. Moreover, the synergistic effect of CuCo bimetal could accelerate redox cycles of Cu+/Cu2+ and Co2+/Co3+, inducing the generation of abundant oxygen vacancies (OVs), thus enhancing PMS activation performance. Three potential TC degradation pathways were proposed according to fifteen possible intermediates detected by liquid chromatography-mass spectrometry (LC-MS). In brief, this work provides an efficient CuCo@GCNs heterogeneous catalyst and a new insight into PMS activation, which extends the application of bimetallic materials for environmental remediation.

A robust in-situ catalytic graphitization combined with salt-template strategy towards fast lithium-ions storage

Lithium-ion hybrid supercapacitors (LIHSs) have received significant attention in electrochemical energy-related areas. However, the sluggish anode kinetics hinders the improvement of power density and cycling stability. Herein, an in-situ catalytic graphitization with a salt-template strategy was applied to prepare the porous graphitic carbon nanosheets. The results demonstrated that the addition of KCl led to a higher specific surface area and higher porous structure. The as-prepared potassium-induced porous graphitic carbon flakes (PPGCs) exhibited an electrochemical plateau capacity of 240.1 mAh g −1 and an electrochemical slope capacity of 129.0 mAh g −1 . PPGCs also delivered superior rate performance of 60.8 mAh g −1 even at 5.0 A g −1 , which was much better than graphitic carbon flakes (GCFs) and potassium-induced graphitic carbon flakes (PGCFs). When assembled into LIHSs devices with commercial activated carbon, the energy density reached 75.6 Wh kg −1 , and the power density was as high as 5.05 kW kg −1 . After 10,000 cycles at 5.0 A g −1 , the energy density was maintained at 39.2 Wh kg −1 , revealing excellent long-term cycling performance. This work may provide a promising solution to obtain graphitic carbon with a high graphitization degree and highly porous structure. • In-situ catalytic graphitization incorporated into salt-template strategy was developed. • Porous graphene-like graphitic carbon nanosheets were achieved successfully. • The effect of KCl added before and after hydrothermal procedure was illustrated. • The energy density reached 75.6 Wh kg −1 with 68.4% retention after 10,000 cycles.

Microwave (MW)-assisted design of cobalt anchored 2D graphene-like carbon nanosheets (Co@GCNs) as peroxymonosulfate activator for tetracycline degradation and insight into the catalytic mechanism

Developing a rapid and cost-effective strategy to design catalysts for advanced oxidation processes (AOPs) has significant implications for environmental remediation. In this study, cobalt anchored 2D graphene-like carbon nanosheets (Co@GCNs) catalysts were fabricated by simple coordination of metal precursors into agarose through microwave (MW)-assisted method to activate peroxymonosulfate (PMS) for tetracycline (TC) degradation. Among them, the Co@GCN-1 exhibited excellent dispersibility and catalytic performance. The Co@GCN-1/PMS system could completely degrade TC (20 mg L–1) within 20 min, whose reaction rate constant (0.273 min−1) was about 6.5 times that of the Co3O4/PMS system (0.0362 min−1) and 14.1 times of the GCN/PMS system (0.0194 min−1), respectively. Additionally, the degradation performance was applicable in a wide pH range (3.84–9.03) and still reached an efficiency of>90% after five cycles. Non-radical pathway represented by 1O2 served as the main contributor to TC degradation besides radicals (i.e., SO4−, OH, and O2−). Density functional theory (DFT) calculations unveiled the synergistic interaction of Co@GCNs, where 2D GCNs as electron mediators promoted the Co3+/Co2+ cycle. Based on the LC-MS analysis, three main degradation pathways of TC including fourteen possible intermediates were proposed based on different ROS reactions. This work provides a facilely prepared and promising 2D metal-based carbonous catalyst to activate PMS for the efficient degradation of TC.

Insight into the effect of clay mineral structure on clay-derived N-doped carbon materials and their efficient electrocatalytic performance

This study aimed to use clay-organic pollutants complex as precursor to fabricate clay-derived N-doped carbon materials, which would reduce the environmental risk of the complex. Kaolinite, sepiolite, montmorillonite as well as iron-saturated montmorillonite were chosen as of the representative clay minerals source. And organic pollutant (tetracycline, TC) was chosen as carbon source. The results revealed the effect of the types of clay minerals and the interaction between TC and clay mineral on the structure and electrocatalytic performance of clay-derived N-doped carbon materials. With the template of layered structural montmorillonite and kaolinite, the obtained carbon materials (NC-MT and NC-KL) possess typically mesoporous structure. With the template of tunnel-like structural sepiolite, NC-SEP exhibited abundant hollow carbon bubbles and mesoporous structure features. Owing to the synergistic effect of iron oxide and montmorillonite in iron-saturated montmorillonite, NC-FEMT showed a graphene-like carbon nanosheet structure with abundant wrinkles and pores. TC might be more easily converted into N-doped clay-derived carbon material, which was partly intercalated into the interlayer of montmorillonite. Besides, the presence of Fe was good for the enhancement of graphitization degree and the generation of active nitrogen species. Moreover, the clay-derived N-doped carbon material presented good oxygen reduction reaction (ORR) electrocatalytic performance.