One-step Pyrolysis Method Research Articles

Constructing In2S3/CdS/N-rGO Hybrid Nanosheets via One-Pot Pyrolysis for Boosting and Stabilizing Visible Light-Driven Hydrogen Evolution

The construction of hybrid junctions remains challenging for the rational design of visible light-driven photocatalysts. Herein, In2S3/CdS/N-rGO hybrid nanosheets were successfully prepared via a one-step pyrolysis method using deep eutectic solvents as precursors. Benefiting from the surfactant-free pyrolysis method, the obtained ultrathin hybrid nanosheets assemble into stable three-dimensional self-standing superstructures. The tremella-like structure of hybrid In2S3/N-rGO exhibits excellent photocatalytic hydrogen production performance. The hydrogen evolution rate is 10.9 mmol·g−1·h−1, which is greatly superior to CdS/N-rGO (3.7 mmol·g−1·h−1) and In2S3/N-rGO (2.6 mmol·g−1·h−1). This work provides more opportunities for the rational design and fabrication of hybrid ultrathin nanosheets for broad catalytic applications in sustainable energy and the environment.

Critical impact of pyrolysis temperatures on biochars for peroxymonosulfate activation: Structural characteristics, degradation performance and mechanism

In order to gain insights into the critical impact of pyrolysis temperatures, a series of pine needle biochars were prepared by one-step pyrolysis method at different temperatures, and were applied for peroxymonosulfate activation to degrade enrofloxacin. Interestingly, with the increase of temperature, the degradation efficiencies increase first, then slightly decrease. BC-700 (biochar synthesized at 700 °C) exhibited best performance, and the degradation rate could reach 97.7 % within 180 min under the optimized conditions. Characterization results demonstrated biochar synthesized at relatively low temperature exhibited more oxygen-containing functional groups and persistent free radicals, while biochar synthesized at high temperature contained more pore structure and higher graphitization degree. Mechanism studies demonstrated that biochar synthesized at relatively low temperature tend to generate transient radicals, while biochar synthesized at high temperature exhibited better electron transfer capability, which might be the key factor of the superior degradation rate of BC-700. In addition, singlet oxygen played an important role in both systems.

Industrial Waste-Derived Carbon Materials as Advanced Electrodes for Supercapacitors.

Strategically upcycling industrial wastes such as petroleum coke and dye wastewater into value-added materials through scalable and economic processes is an effective way to simultaneously tackle energy and environmental issues. Doping carbon electrodes with heteroatoms proves effective in significantly enhancing electrochemical performance through alterations in electrode wettability and electrical conductivity. This work reports the use of dye wastewater as the sole dopant source to synthesize N and S co-doped petroleum coke-based activated carbon (NS-AC) by the one-step pyrolysis method. More importantly, our wastewater and petroleum coke-derived activated carbon produced on a large scale (20 kg/batch) shows a specific surface area of 2582 m2 g-1 and an energy density of about 95 Wh kg-1 in a soft-packaged full cell with 1 M TEATFB/PC as the electrolyte. The scalable production method, together with the green and sustainable process, can be easily adopted and scaled by industry without the need for complex processes and/or units, which offers a convenient and green route to produce functionalized carbons from wastes at a low cost.

Synthesis of magnetic biochar-supported Fe-Cu bimetallic catalyst from pulp and paper mill wastes for the Fenton-like removal of rhodamine B dye

Treating the wastes generated from pulp and paper mills, such as black liquor and Fenton sludge is challenging. In this study, the biochar-supported Fe-Cu bimetallic catalysts were synthesized by a one-step pyrolysis method using Fenton sludge as iron source, acid-precipitated black liquor (APBL) as carbon source and copper nitrate as copper source. The catalysts were used to remove rhodamine B (RhB) dye from aqueous solution by Fenton-like reaction. The optimal catalyst (FeCu@BC600-2) was pyrolyzed at 600 °C with an Fe/Cu mixing ratio of 2 and consisted of mesoporous biochar supported nanoscale Fe3O4 and Cu0. It had a specific surface area of 104.6 m2·g−1 and a saturation magnetization of 33.3 emu·g−1. In the FeCu@BC600-2/H2O2 system, RhB dye (10 mg·L-1) was completely removed within 60 min at acidic pH (initial pH 3, 0.2 g·L-1 catalyst, 1 mM H2O2) or 6 h at neutral pH (initial pH 7, 0.25 g·L-1 catalyst, 25 mM H2O2) at 30 °C. Moreover, the FeCu@BC600-2 exhibited good magnetic separation ability, low metal leaching, excellent reusability and broad applicability to other synthetic dyes. The dye removal mechanism involved the synergistic effect of adsorption and catalytic oxidation (especially heterogeneous catalytic oxidation). At acidic pH, RhB degradation was due to •OH radical, which was generated from the activation of H2O2 by ≡Cu(I) or Cu(I) oxidized from Cu0 and ≡Fe(II) in Fe3O4. At neutral pH, RhB degradation was mainly due to •OH and 1O2 with the former being produced by ≡Cu(I) and ≡Fe(II). Furthermore, Cu(I) oxidized from Cu0 and the active functional groups (such as sp2 C = C) in the biochar facilitated the reduction of Fe(III) to Fe(II), resulting in a high catalytic oxidation efficiency.

Silver Nanoparticle Decorated Perforated Graphene: An Efficient and Low-Cost Catalyst for Hydrogen Evolution Reaction

Recently, the fabrication of noble-metal-free, Earth-abundant, inexpensive, and efficient electrocatalysts for hydrogen evolution reaction (HER) has become a challenge for clean and sustainable energy applications. This report details the one-step pyrolysis method for producing perforated graphene (PG) using dead Bougainvillea bracts (natural waste) without activating agents. The properties of the as-prepared PG are studied through basic and electrochemical characterizations. In addition, silver nanoparticles (Ag NPs) are attached to it in weight ratios of 1:5 and 1:8, resulting in a composite catalyst that exhibits notable activity towards HER. The electrochemical performances of the catalysts reveal that PG:Ag 1:5 displays superior electrocatalytic HER activity in an acidic medium, with an onset potential of approximately −143 mV, an overpotential of 327 mV to achieve a current density of 10 mA cm−2, and a Tafel slope of around 125 mV dec−1. In order to assess its stability, the optimized catalyst was subjected to a chronoamperometric study for a duration of 104 s. This study presents a simple and effective way to produce hydrogen sustainably from electrochemical water splitting, using efficient, stable, environmentally friendly, abundant, and low-cost catalysts.

Removal of Phosphorus from Domestic Sewage in Rural Areas Using Oyster Shell-Modified Agricultural Waste–Rice Husk Biochar

In order to promote the improvement of rural living environments, the treatment of rural domestic sewage has attracted much attention in China. Meanwhile, the rural regions’ sewage discharge standards are becoming increasingly stringent. However, the standard compliance rate of the total phosphorus (TP) is very low, and the TP has become the main limiting pollutant for the water pollutant discharge standards of rural domestic sewage treatment facilities. In this study, oyster shell waste was employed as a calcium source, and agricultural waste–rice husk was used as a carbon source to synthesize calcium-modified biochar adsorbent materials (Ca-BC) by a simple one-step pyrolysis method. The resultant Ca-BC adsorbent materials demonstrated efficient phosphate (P) adsorption from aqueous solutions over a wide pH range (3–11) and adsorption selectivity. Ca-BC’s adsorption capacity for P increased with the pyrolysis temperature, increasing from 700 °C to 900 °C, which was attributed to the higher specific surface area and calcium oxide content at higher pyrolysis temperatures. The Ca-BC sample, which was made from oyster shells and rice husks with a mass ratio of 2:1 and a pyrolysis temperature of 900 °C, had a maximum adsorption capacity of 196.2 mg/g. The Langmuir model and pseudo-second-order model were the best at describing the adsorption process, and the predominant sorption mechanism for P is the precipitation of calcium oxide or calcium hydroxide with phosphate to create hydroxyapatite. Ca-BC can effectively remove P from rural domestic sewage. The removal rate of the total phosphorus (TP) in rural domestic sewage is 93.9–99.4%. After the adsorption treatment, the discharge of the TP in the rural sewage met the second-grade (TP < 3 mg/L) or even the first-grade (TP < 2 mg/L) Discharge Standard of Water Pollutants for Centralized Rural Sewage Treatment Facilities (DB33/973-2021). This study provides an experimental basis for efficient P removal by Ca-BC adsorbent materials and suggests possible applications in rural domestic sewage.

One-step synthesis of lychnophora residue-derived porous carbon sheets for highly efficient removal of copper(Ⅱ)

In this study, the lychnophora residue-derived porous carbon sheets (LRPCSs) were synthesized using a facile one-step pyrolysis method, and the physicochemical properties of LRPCSs were analyzed via various characterization apparatus, its adsorption behaviors and mechanism for copper(Ⅱ) (Cu(II)) were also investigated. The LRPCSs possessed three-dimensional honeycomb sheet structure, a specific surface area of 14.6 m2·g−1, abundant mineral elements (K, Ca, and Mg), and the oxygen- and sulfur-containing functional groups, which would offer more active sites for the fast adsorption of Cu(II). Batch experiments demonstrated that the adsorption properties of Cu(II) by LRPCSs raised with the raising of biochar dose, pH value (2−6), Cu(II) concentration, and temperature. The isotherms and kinetics studies showed that the adsorption data conformed very well to Langmuir isotherm (R2 ≥0.9975) and pseudo-second-order kinetic models (R2 ≥0.9941). The maximum Cu(II) adsorption capacities of LRPCSs were respectively 103.09, 120.48, and 153.85 mg·g−1 at 298, 308, and 318 K, which were superior to previously reported biochar adsorbents. The thermodynamic studies indicated that the Cu(II) adsorption with LRPCSs was an automatic, endothermal, and entropy-raising process (ΔG° = −6.82∼−8.47 kJ·mol−1, ΔH° = 17.89 kJ·mol−1, ΔS° = 83.07 J·(mol·K)−1). The adsorption capacity of Cu(II) with LRPCSs still remained 85% after four adsorption-desorption cycles. Furthermore, the ion exchange and surface complexation were the predominant mechanism for the Cu(Ⅱ) adsorption by LRPCSs, with cation-π interaction and pore capture playing a secondary role. This study showed that LRPCSs could be an effective, low-cost, and reusable adsorbent with great potential for application in remediating the Cu(II)-containing wastewater pollution.

Facile One-Step Pyrolysis of ZnO/Biochar Nanocomposite for Highly Efficient Removal of Methylene Blue Dye from Aqueous Solution.

In this work, we developed a facile one-step pyrolysis method for preparing porous ZnO/biochar nanocomposites (ZBCs) with a large surface area to enhance the removal efficiency of dye from aqueous solution. Peanut shells were pyrolyzed under oxygen-limited conditions with a molten salt ZnCl2, which played the roles of the activating agent and precursor for the formation of nanoparticles. The effects of the mass ratio between the molten salt ZnCl2 and peanut shells as well as pyrolysis temperature on the formation of ZBCs were investigated. Characterization results revealed that the as-synthesized ZBCs exhibited a highly porous structure with a specific surface area of 832.12 m2/g, suggesting a good adsorbent for efficient removal of methylene blue (MB). The maximum adsorption capacity of ZBCs on MB was 826.44 mg/g, which surpassed recently reported adsorbents. The formation mechanism of ZnO nanoparticles on the biochar surface was due to ZnCl2 vaporization and reaction with water molecules extracted from the lignocellulosic structures. This study provides a basis for developing a simple and large-scale synthesis method for wastewater with a high adsorption capacity.

Magnetic porous carbon materials derived from metal-organic framework in-situ growth on natural cellulose of wood for sulfadiazine degradation: Role of delignification and mechanisms

Magnetic porous carbon materials as peroxymonosulfate (PMS) activators for sulfadiazine degradation were derived from metal-organic frameworks (MOFs) grown in-situ on the cellulose of wood through the one-step pyrolysis method. The cellulose was obtained by treating wood powder with sodium chlorite to remove lignin, and Fe-MOFs (MIL-101(Fe)) nanoparticles were in-situ grown on the cellulose through hydrothermal reaction. The delignification of wood effectively enhanced the in-situ growth of MIL-101(Fe) on the wood tracheid skeleton, increased the specific surface area of magnetic porous carbon material (Fe@PC-50) after pyrolysis, and improved the performance of Fe@PC-50 as a PMS activator for the degradation of sulfadiazine. With the presence of 0.04 g L−1 Fe@PC-50 and 0.12 g L−1 PMS, the degradation percentage of sulfadiazine (20 mg L−1) could reach 100 % within 15 min, indicating excellent catalytic activity. Quenching tests and electron paramagnetic resonance (EPR) indicated that both free and non-free radicals played important roles in PMS activation. X-ray photoelectron spectroscopy (XPS) suggested that Fe0 and Fe3C were the possible important active sites for sulfadiazine degradation. This work offered an effective method to synthesize PMS activators from biomass/MOF materials for water treatment.

Magnetic Biochar Derived from Fenton Sludge/CMC for High-Efficiency Removal of Pb(II): Synthesis, Application, and Mechanism

Magnetic biochar composites (MBC) were developed by a simple one-step pyrolysis method using Fenton sludge waste solid and carboxymethyl cellulose sodium. Detailed morphological, chemical, and magnetic characterizations corroborate the successful fabrication of MBC. Batch adsorption experiments show that the synthesized MBC owns high-efficiency removal of Pb(II), accompanied by ease-of-separation from aqueous solution using magnetic field. The experiment shows that the equilibrium adsorption capacity of MBC for Pb(II) can reach 199.9 mg g−1, corresponding to a removal rate of 99.9%, and the maximum adsorption capacity (qm) reaches 570.7 mg g−1, which is significantly better than that of the recently reported magnetic similar materials. The adsorption of Pb(II) by MBC complies with the pseudo second-order equation and Langmuir isotherm model, and the adsorption is a spontaneous, endothermic chemical process. Investigations on the adsorption mechanism show that the combination of Pb(II) with the oxygen-containing functional groups (carboxyl, hydroxyl, etc.) on biochar with a higher specific surface area are the decisive factors. The merits of reusing solid waste resource, namely excellent selectivity, easy separation, and simple preparation make the MBC a promising candidate of Pb(II) purifier.

Highly sensitive detection of microRNA-21 by nitrogen-doped carbon dots-based ratio fluorescent probe via nuclease-assisted rolling circle amplification strategy

Highly sensitive and selective detection of microRNA-21 (miRNA-21) in biological samples is critical for the disease diagnosis and cancer treatment. In this study, a nitrogen-doped carbon dots (N-CDs)-based ratio fluorescence sensing strategy was constructed for miRNA-21 detection with high sensitivity and excellent specificity. Bright-blue N-CDs (λex/λem = 378 nm/460 nm) were synthesized by facile one-step microwave-assisted pyrolysis method by using uric acid as the single precursor, and the absolute fluorescence quantum yield and fluorescence lifetime of N-CDs were 35.8% and 5.54 ns separately. The padlock probe hybridized with miRNA-21 firstly and then was cyclized by T4 RNA ligase 2 to form a circular template. At the present of dNTPs and phi29 DNA polymerase, the oligonucleotide sequence in miRNA-21 was prolonged to hybridize with the surplus oligonucleotide sequences in circular template, generating long and reduplicated oligonucleotide sequences containing abundant guanine nucleotides. Separate G-quadruplex sequences were generated after the addition of Nt.BbvCI nicking endonuclease, and then hemin bound with G-quadruplex sequence to construct the G-quadruplex DNAzyme. Such G-quadruplex DNAzyme catalyzed the redox reaction of o-phenylenediamine (OPD) with H2O2, finally producing the yellowish-brown 2,3-diaminophenazine (DAP) (λem = 562 nm). Due to the inner filter effect between N-CDs and DAP, the ratio fluorescence signal of DAP with N-CDs was utilized for sensitive detection of miRNA-21 with detection limit of 0.87 pM. Such approach has practical feasibility and excellent specificity for miRNA-21 analysis during highly homological miRNA family in HeLa cell lysates and human serum samples.

CoZn-ZIF and melamine co-derived double carbon layer matrix supported highly dispersed and exposed Co nanoparticles for efficient degradation of sulfamethoxazole

Metal-organic framework (MOF)-derived carbon materials have drawn tremendous attention as activators of peroxymonosulfate (PMS) for the degradation of antibiotics. However, it is still challenging to construct MOF-derived materials with well-dispersed and highly-exposed metal active sites. Herein, the bimetallic Cobalt-Zinc-zeolite imidazolate framework and melamine co-derived double layer nitrogen-doped porous carbon matrix supported highly dispersed cobalt nanoparticles (Co NPs) (denoted as Co-NC-C) with the exposure of more Co NPs sites was developed by one-step pyrolysis method. The transmission electron microscopy results demonstrate that double layer carbon matrix as a dispersant can effectively inhibit the agglomeration of Co NPs, and Co-NC-C possessed more exposure of Co active sites compared with Co-NC without melamine. Co-NC-C efficiently activated PMS to remove over 96.67% of sulfamethoxazole (SMX) at a widespread range of pH within 120 min due to its the highly-exposed Co active sites and high graphitization degree. Additionally, the degradation mechanism dominated by the singlet oxygen was demonstrated. Finally, four products and two probable degradation pathways of SMX were confirmed. Half of the products were less toxic than SMX based on the ecological structure activity relationships analysis results. The study provides valuable insights for the development of MOF-derived catalysts with well-dispersed and highly-exposed metal active sites.

Removal of gatifloxacin by activated peroxymonosulfate using co-pyrolysis materials of water treatment residuals and biomass: Nonradical-dominated mechanisms enhanced by adsorption

Magnetic porous biochar derived from water treatment residuals and corn stalk (WTR-CS) was prepared by one-step pyrolysis method and applied for peroxymonosulfate (PMS) activation for gatifloxacin (GAT) removal. The results demonstrated that the adsorption and degradation efficiency of the WTR-CS/PMS system increased with the increasing pyrolysis temperature by changing their porosity, iron species and carbon configurations. WTR-CS obtained at 1000 °C (WTR–CS–1000) exhibited the best GAT removal effect, slight Fe leaching, strong stability and reusability. About 42.77% of GAT (40 mg L−1) was removed in the adsorption phase and 95.12% in total (90 min), accompanied by a 77% reduction in total organic carbon (TOC). The kinetic analysis demonstrated that adsorption was a key step in the overall catalytic process. Based on the quenching experiments, ESR and electrochemical tests, free radicals (SO4•-, ·OH and O2•-) and nonradical (1O2 and electron transfer) pathways jointly acted in the reaction, and nonradical pathway was dominant in the reaction. Four degradation pathways were proposed based on the intermediates detected by LC-MS, and the eco-toxicity of degradation intermediates was predicted by ECOSAR program. This study provides a new strategy for simultaneous iron-containing WTRs resource utilization and pollutant removal by synergistic adsorption and oxidative degradation.

Natural mineral-derived Fe/Mn-BC as efficient peroxydisulfate activator for 2,4-dichlorophenol removal from wastewater: Performance and sustainable catalytic mechanism

Iron and manganese oxides/biochar composite materials (Fe/Mn-BC) are promising catalysts in the field of advanced oxidation. High purity chemical reagents are popular precursors for preparing Fe/Mn-BC, while the potential of low-cost natural minerals as precursors has been neglected. In this study, high-efficiency Fe/Mn-BC was synthesized by one-step pyrolysis method using hematite, phosphoromanganese, and bagasse. The synthesized Fe/Mn-BC removed 83.7% 2, 4-dichlorophenol (2, 4-DCP) within 30 min, about 8.8 and 10.6 times better than biochar (BC) and Fe/Mn complex, respectively. The removal of 2, 4-DCP in the Fe/Mn-BC + peroxydisulfate (PDS) system was influenced by catalyst dosage, PDS concentration, initial pH, organic acids, and chromium. Sulfate radical (SO4•-) and hydroxyl radicals (•OH) generated by Fe/Mn-BC-activated PDS have similar contribution to the degradation of 2,4-DCP. A possible removal mechanism of 2, 4-DCP in the Fe/Mn-BC + PDS system was proposed based on Electron Spin Resonance spectroscopy, free radical quenching experiments, X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical measurement. Fe0 and Fe(II) in Fe/Mn-BC play significant role in catalytic degradation of 2, 4-DCP at the early stage of the reaction (within 0–5 min). Then, the interaction between Mn and BC or structural Mn and structural Fe gradually became dominant in the later stage. Similarly, the electron transfer promoted by biochar also played an important role in this catalysis. This discovery provided a new strategy for developing iron and manganese oxides/biochar composite materials to activate PDS for the elimination of refractory organic pollutants.

A Double Atomic-Tuned RuBi SAA/Bi@OG Nanostructure with Optimum Charge Redistribution for Efficient Hydrogen Evolution.

Charge redistribution on surface of Ru nanoparticle can significantly affect electrocatalytic HER activity. Herein, a double atomic-tuned RuBi SAA/Bi@OG nanostructure that features RuBi single-atom alloy nanoparticle supported by Bi-O single-site-doped graphene was successfully developed by one-step pyrolysis method. The alloyed Bi single atom and adjacent Bi-O single site in RuBi SAA/Bi@OG can synergistically manipulate electron transfer on Ru surface leading to optimum charge redistribution. Thus, the resulting RuBi SAA/Bi@OG exhibits superior alkaline HER activity. Its mass activity is up to 65000 mA mg-1 at an overpotential of 150 mV, which is 72.2 times as much as that of commercial Pt/C. DFT calculations reveal that the RuBi SAA/Bi@OG possesses the optimum charge redistribution, which is most beneficial to strengthen adsorption of water and weaken hydrogen-adsorption free energy in HER process. This double atomic-tuned strategy on surface charge redistribution of Ru nanoparticle opens a new way to develop highly efficient electrocatalysts.

Facile Pyrolysis Treatment for the Synthesis of Single-Atom Mn Catalysts Derived from a Hyperaccumulator

Advanced oxidation processes (AOPs) have revealed wide prospects in the application of the degradation of organic contaminants in ground water and soil. High-performance, environmentally friendly, and low-cost single-atom catalysts (SACs) are promising approaches to active persulfate in AOPs. However, the practical application of SACs is restricted by high preparation costs and tedious procedures. Herein, a manganese (Mn) hyperaccumulator, Phytolacca americana, was successfully exploited as a precursor to synthesize a novel Mn SAC (SPBC-700N) via a one-step pyrolysis method. In SPBC-700N, Mn atoms are dispersed atomically upon the carbon matrix and coordinate with four N atoms to form Mn–N4 active sites, which exhibits an extraordinary catalytic activity for peroxymonosulfate (PMS) activation. A large number of reactive oxygen species are formed during the reaction, and over 90% of the antibiotic (chloroquine phosphate/CQP) could be removed within 30 min. The superior catalytic performance of the Mn SAC/PMS system for CQP degradation is ascribed to the synergistic effect of the maximized utilization of Mn atoms and the neighboring pyrrolic N sites, as identified by X-ray absorption fine structure spectroscopy and density function theory calculations. This work not only provides a green and low-cost strategy for synthesizing SACs but also gives an atomic-level insight into the catalytic activity of the Mn–N4 sites for PMS activation.

Mn–N–C catalysts derived from metal triazole framework with hierarchical porosity for efficient oxygen reduction

Manganese and nitrogen co-doped porous carbon (Mn–N–C) are proposed as one of the most up-and-coming non-precious metal electrocatalysts to substitute Pt-based in the oxygen reduction reaction (ORR). Herein, we chose metal triazole frameworks as carbon substrate with hierarchical porosity for trapping and anchoring Mn-containing gaseous species by a mild one-step pyrolysis method. The optimized Mn–N–C electrocatalyst with a large metal content of 1.71 wt% and a volume ratio of 0.86 mesopores pore delivers a superior ORR activity with a half-wave potential (E 1/2) of 0.92 V in 0.1 M KOH and 0.78 V in 0.1 M HClO4. Moreover, the modified Mn–N–C catalyst showed superior potential cyclic stability. The E 1/2 remained unchanged in 0.1 M KOH and only lost 6 mV in 0.1 M HClO4 after 5000 cycles. When applied as the cathode catalyst in Zn-air battery, it exhibited a maximum peak power density of 176 mW cm−2, demonstrating great potential as a usable ORR catalyst in practical devices.

WOx nanoparticles coupled with nitrogen-doped porous carbon toward electrocatalytic N2 reduction.

The electrocatalytic nitrogen reduction reaction (eNRR) is a sustainable and green alternative to the traditional Haber-Bosch process. However, the chemical inertness of nitrogen gas and the competitive hydrogen evolution reaction significantly limit the catalytic performance of eNRR. Although tungsten oxide-based eNRR catalysts could donate unpaired electrons to the antibonding orbitals of N2 and accept lone electron pairs from N2 to dissociate NN triple bonds, the low electrical conductivity and the influence of the variable valence of W still affect the catalytic activity. Herein, a high-performance eNRR catalyst WOx nanoparticle/nitrogen-doped porous carbon (WOx/NPC) was prepared by a one-step thermal pyrolysis method. The results reveal that WOx gradually changes from the dominant WO2 phase to the WO3 phase. WOx/NPC-700 °C with WO2 NPs anchored on the surfaces of NPC via W-N bonding could deliver a high NH3 yield of 46.8 μg h-1 mg-1 and a high faradaic efficiency (FE) of 10.2%. The edge W atomic site on WOx/NPC is demonstrated to be the active center which could activate a stable NN triple bond with an electron-donating ability. Benefiting from the covalent interaction between the WOx nanoparticles and NPC, WOx/NPC also shows high electrocatalytic stability.

Electron transfer mechanism mediated nitrogen-enriched biochar encapsulated cobalt nanoparticles catalyst as an effective persulfate activator for doxycycline removal

To address the current water pollution issues, one of the most important technologies is the development of efficient and environmental-friendly catalysts for the treatment of organic pollutants in water. In this study, a nitrogen-enriched biochar encapsulated cobalt nanoparticles composite (Co@N-BC) was synthesized using a one-step pyrolysis method based on metal-organic frameworks (MOFs) and leaf biomass as precursors. The obtained Co@N-BC possessed more functional group, large specific surface area and less cobalt ion leaching, which were used for efficient persulfate (PS) activation for approximately 92.72% DOX (50 mg/L) removal in 30 min. The quenching test, electron paramagnetic resonance (EPR), and electrochemical characterization of the Co@N-BC/PS system revealed that electron transfer was the primary pathway for DOX elimination. Moreover, the Co@N-BC/PS system had satisfactory stability in a wide pH range (2–10) and was not adversely affected by the various anions or water matrix. This research will shed new light on the design and development of MOF derivatives, as well as provide technical support for the eradication of antibiotics.

Heterogeneous catalytic activation of persulfate for the removal of rhodamine B and diclofenac pollutants from water using iron-impregnated biochar derived from the waste of black seed pomace

Waste reutilization in environmental remediation is highly desired as a new strategy in the scientific community for environmental applications. Industrial biowaste has been used significantly to produce biochar, which can be used in environmental remediation. In this study, a low-cost iron-impregnated modified biochar (FeBS800) was successfully prepared using a one-step pyrolysis method with waste black seed pomace as a “waste-to-resource” strategy and applied to activate peroxydisulfate (PDS) for the degradation and mineralization of rhodamine B (RhB) and diclofenac (DCF) in water. The physicochemical properties of the FeBS800 catalyst were investigated by various characterization analytical methods. The developed FeBS800 catalyst exhibits excellent catalytic activity and good stability in PDS activation. In the FeBS800/PDS system, the degradation efficiency within 10 min reached up to 98.2 % and 88.3 %, while the mineralization efficiencies within 30 min reached 48 % and 68.7 % for 20 mg/L RhB and DCF, respectively, with slight iron ions leaching of less than 3 mg/L. The optimum removal conditions of the FeBS800/PDS system were found to be 1.5 g/L catalyst dose and 10 mM PDS initial concentration at circumneutral pH solution. Moreover, the radical quenching experiment revealed that the main reactive oxygen species (ROS) responsible for the pollutants’ degradation in FeBS800/PDS system are in the order of 1O2 > •OH > O2•- > SO4•-, while singlet oxygen plays a leading role. The degradation kinetics of both pollutants (RhB and DCF) were well-fitted to the pseudo-first-order model. Furthermore, a possible mechanism pathway of PDS activation for generation ROS in the FeBS800/PDS system was proposed. Overall, the research results suggested that the modified FeBS800 could have a promising potential in activating PDS for the removal of refractory organic pollutants from water.