One-step Pyrolysis Method Research Articles

Synthesis of in situ grown CNTs on MOF-derived Ni@CNT with tailorable microstructures toward regulation of electromagnetic wave absorption performance

Metal-Organic framework (MOF) derivatives have been applied as electromagnetic wave absorption (EMA) materials in recent years. Carbon nanotubes (CNTs) can achieve in situ growth on the surface of MOF derivatives. However, there is limited research on the EMA performance by regulating the morphology of the in situ grown CNTs. In this work, we prepared MOF-derived Ni@carbon nanotubes (Ni@CNT) with controllable length of CNTs by solvothermal and simple one-step pyrolysis method and revealed the CNT growth mechanism. We further investigated the effect of in situ grown CNT morphology on electromagnetic parameters and EMA performance. In situ grown CNTs of similar length on the surface of MOF derivatives lead to similar electromagnetic parameters. When the length of CNTs is short, the relaxation strength (Δε=εs−ε∞) is high, leading to excellent microwave absorption performance. For Ni@CNT-600, the reflection loss of −44.4 dB can be achieved at merely 1.72 mm. Finite element (FE) simulation was used to evaluate the EMA mechanism of different samples by calculating electric field and polarization strength. This work has explored the electromagnetic wave absorption performance from the perspective of microstructural tailoring, helpful for understanding the unique role of the in situ grown CNTs on the surface of MOF derivatives and investigating the ultra-thin electromagnetic wave absorption materials.

High loading and sustained-release system of doxorubicin-carbon dots as nanocarriers for cancer therapeutics

Nanocarriers for drugs have been investigated for decades, yet it is still challenging to achieve sustained release from nanomaterials due to drug loading inefficiency and burst release. In this study, we developed novel functional carbon dots (CDs) and investigated the therapeutic efficacy by studying the loading efficiency and release behavior of the anticancer drug doxorubicin (DOX). CDs were successfully synthesized using a one-step pyrolysis method with varying concentrations of citric acid (CA) and thiourea (TU). Functional groups, morphology, particle size, and zeta potential of synthesized CT-CDs and DOX loaded CT-CDs were investigated by UV-visible, Fluorescence, dynamic light scattering, Zeta Potential measurements, FTIR, and transmission electron microscopy. The zeta potential data revealed DOX loading onto CT-CDs by charge difference, i.e. -24.6 ± 0.44 mV (CT-CDs) and 20.57 ± 0.55 mV (DOX-CT-CDs). DOX was loaded on CDs with a loading efficiency of 88.67 ± 0.36%.In vitrodrug release studies confirmed pH-dependent biphasic drug release, with an initial burst effect and sustained release of DOX was found to be 21.42 ± 0.28% (pH 5), 13.30 ± 0.03% (pH 7.4), and 13.95 ± 0.18% (pH 9) even after 144 h at 37 °C. The CT-CDs were non-toxic and biocompatible with L929 Fibroblasts cells. The cytotoxic effect of DOX-CT-CDs showed a concentration-dependent effect after 48 h with Glioblastoma U251 cells. Flow cytometry was used to examine the cellular uptake of CT-CDs and DOX-CT-CDs in L929 and U251 cells. It was observed that the maximum CT-CDs uptake was around 75% at the end of 24 h. This study showed that the synthesized fluorescent CT-CDs demonstrated a high drug loading capacity, pH-dependent sustained release of DOX, and high cellular uptake by mammalian cells. We believe this work provides practical and biocompatible CDs for chemotherapeutic drug delivery that can be applied to other drugs for certain therapeutic aims.

A high-capacity and stable dual-ion battery based on an ultra-large lattice-spacing amorphous carbon anode

Compared with traditional lithium-ion batteries (LIBs), dual-ion batteries (DIBs) offer advantages such as high operating voltage, good safety performance, and low cost. However, DIBs often suffer from challenges such as low specific capacity and poor cycling performance in practical applications. Here, a layered nitrogen-doped carbon anode has been prepared using a one-step pyrolysis method with excellent Li+ storage sites. The large lattice spacing of 0.55 nm provides more space for the storage and migration of active ions. Concurrently, the utilization of concentrated electrolyte facilitated the electrochemical window and the restrained solvation of ions, which helps to boost ion transport and improve the stability of the electrolyte and the operating voltage of DIBs. The assembled DIBs exhibit a high specific discharge capacity of 179.27 mA h g−1, within a 2.5–4.8 V voltage range, and excellent cycling stability of 3500 cycles without degradation. Specifically, the structural evolution of the electrodes during charging and discharging and the working mechanism of the DIBs are also explored. The DIBs system designed in this paper provides a facile and scalable approach to promote the development of DIBs with low-cost and high-performance.

Manipulation in local coordination of platinum single atom enables ultrahigh mass activity toward hydrogen evolution reaction

Atomic-engineering of noble metal into single-atom electrocatalysts with well-defined active sites has been considered as an effective approach to enhance the mass-activity towards hydrogen evolution reaction (HER), crucial for the practical implementation of this sustainable technology. Herein, we devise a metallic-coordination strategy via a facile one-step pyrolysis method, for the atomic isolation of a small amount of platinum (Pt, 0.45 wt%) atoms in the surface of nickel (Ni) nanoparticles (Pt1@Ni) encapsulated into nitrogen-doped carbon nanotubes (Pt1@Ni/NCNT). Such a Pt1@Ni/NCNT single-atom alloy catalyst exhibits a record-high and all-round superior HER performance including mass-activity (up to 350.7 A mgPt−1@η150), stability (>50 h at 100 mA cm−2), pH-tolerance by comparison with Pt1@NC. Our density functional theory calculations combined with in situ Raman spectroscopic studies reveal a synergistic dual-active-site catalytic mechanism, involving the fast hydrogen spillover effect on coordinated Ni supports and accelerated water dissociation in acidic and alkaline medium, respectively. A strong electronic hybridization of 5d orbital of alloyed Pt and 3d orbital of Ni atoms modulates the d band center of Pt, which not only boosts HER activity but also stabilizes Pt single atoms. Due to the double protecting strategy from strong anchoring effect in Ni support and chemically stable NCNT shell, a robust stability is achieved for Pt1@Ni/NCNT hierarchal catalyst. Our findings open up a new avenue to substantially tailor the activity of surface Pt atoms for the design of highly efficient and durable noble metal-based catalysts.

Selective removal of organic contaminants and ascorbic acid enhancement effect based on the magnetic Fe0/FeS2-doped carbon nanolayer.

Developing highly effective iron-based catalyst to selectively remove organic contaminants has garnered considerable attention. Herein, a magnetic Fe0/FeS2-doped carbon nanolayer (S-Fe@NC) was synthesized through a straightforward one-step pyrolysis method, pyrolyzing a mixture composed of 4,6-dihydroxypyrimidine, trithiocyanuric acid, and FeCl3·6H2O. With the presence of PMS, S-Fe@NC demonstrated the ability to remove almost 100% bisphenol-A (50μM) within 3min, attributed to its excellent graphitization degree and high FeS2/Fe0 content. Furthermore, the S-Fe@NC catalyst demonstrated an impressive kobs value of 1.476min-1, which surpassed the traditional Fenton system by 77 times and even exceeded the commercial Fe0 catalyst by 127 times. More importantly, the S-Fe@NC/PMS system succeeded in selectively removing organic contaminants based on the hydrophobic interaction between catalyst and contaminants. Besides, the result of electron paramagnetic resonance and the radical quenching experiments indicated that ·OH, SO4·-, 1O2, and O2·- were involved in the organic contaminants removal. Interestingly, after adding ascorbic acid (AA) to the S-Fe@NC/PMS system, more ROS could be generated to result in the kobs augmenting by 4.16 times (6.133min-1), completely different from the common sense that AA was usually used as a radical quencher. Additionally, the magnetically separable catalyst also exhibited excellent reusability and broad pH adaptability (2.0-12.0). This study provided a valuable insight for developing highly selective and effective Fe-based catalyst for practical wastewater treatment.

One-step microwave-assisted synthesis of MgO-modified magnetic biochar for enhanced removal of lead and phosphate from wastewater: Performance and mechanisms

Herein, magnesium oxide (MgO) and ferroferric oxide (Fe3O4) functionalized biochar (MgO@MBC) was synthetized through one-step pyrolysis method, which was used to decontaminate lead (Pb) and phosphate in contaminated water. Characterization results exhibited that MgO and Fe3O4 particles were successfully loaded on MgO@MBC, and the magnetism of MgO@MBC was in favor of recycling materials. Experimental results showed that MgO@MBC possessed outstanding adsorption performance with 556.62/303.08 mg/g for Pb(II)/phosphate. Furthermore, MgO@MBC had excellent anti-interference performance under the coexistence of various ions, and superior reusability with over 82 % adsorption efficiency for Pb(II)/phosphate after four regeneration cycles. It demonstrated that the high-efficiency capacity of Pb(II) adsorbed on MgO@MBC was attributable to complexation, electrostatic attraction, precipitation, and pore-filling, while the efficient uptake of phosphate was due to precipitation, pore-filling, and ligand exchange. Based on the above analysis, MgO@MBC was believed to be an outstanding adsorbent for remediating Pb(II)/phosphate wastewater.

Harnessing photocatalytic activity of mesoporous graphitic carbon nitride decorated by copper single-atom catalysts for oxidative dehydrogenation of N-heterocycles

This work describes the application of Cu single-atom catalysts (SACs) for photocatalytic oxidative dehydrogenation of N-heterocyclic amines to the respective N-heteroaromatics through environmentally benign and sustainable pathways. The mesoporous graphitic carbon nitride (mpg-C3N4), prepared by the one-step pyrolysis method, possesses a lightweight material with a high surface area (95 m2 g−1) and an average pore diameter (3.6 nm). A simple microwave-assisted preparation method was employed to decorate Cu single-atom over mpg-C3N4 support. The Cu single-atom decorated on mpg-C3N4 support (Cu@mpg-C3N4) is characterized by various characterization techniques, including XRD, UV–visible spectrophotometry, HRTEM, HAADF-STEM with elemental mapping, AC-STEM, ICP-OES, XANES, EXAFS, and BET surface area. These characterization studies confirmed that the Cu@mpg-C3N4 catalyst exhibited high surface area, mesoporous nature, medium band gap, and low metal loading. The as-synthesized and well-characterized Cu@mpg-C3N4 single-atom photocatalyst is then evaluated for its efficacy in converting N-heterocycles into corresponding N-heteroaromatic compounds with excellent conversion and selectivity (>99 %). This transformation is achieved using water as a green solvent and a 30 W white light as a visible light source, demonstrating the catalyst's potential for sustainable and environmentally benign reactions.

Facile synthesis of coral-like nitrogen and sulfur co-doped carbon-encapsulated FeS2 for efficient electroreduction of nitrate to ammonia

Electro-reduction of nitrate (NO3–) to ammonia is a promising method to transform the environmental contaminant NO3– to value-added ammonia. Since diverse end-products might be formed and a convenient material preparation process is preferable, it is of great importance to facilely synthesize a high-performance electro-catalyst towards ammonia generation with high selectivity. Herein, a coral-like nitrogen (N) and sulfur (S) co-doped carbon-encapsulated FeS2 composite material (FeS2@NSC) was successfully fabricated for effective electro-reduction of high-concentration of NO3– to ammonia through a simple one-step pyrolysis method. The FeS2@NSC-400 material exhibited remarkable electrocatalytic NH3 production performance with the NH3 yield of 4428.35 μg h−1 cm−2 and NH3 Faraday efficiency of 84.75 % at −1.4 V vs. Ag/AgCl, which outperforms many of the reported electrocatalysts. The unique small cluster coral-like core–shell structure, N, S co-doping and the interaction between inner FeS2 and the outer carbon layer greatly enhanced the electrical conductivity and stability of the material and the adsorption of NO3– and intermediate products, thereby facilitating the electrocatalytic performance of nitrate-to-ammonia. The FeS2@NSC material induced the electrocatalytic reduction of NO3– mainly through direct electron transfer instead of the indirect atomic H* mediation, and the main reduction product NH3 was speculated to derive from the pathway of NO3–* → NO2–* → NO* → HNO* → H2NO* → H2NOH* → NH3.

Coal-based hard carbon anode for high-performance sodium ion batteries via coal-based graphene oxide as a multi-functional binder

Coal-based hard carbon for sodium ion batteries (SIBs) was successfully prepared using Shenfu bituminous coal (SFC) by one-step pyrolysis method. In the present work, we reported a novel method to fabricate carbon electrodes for SIBs from coal-based hard carbon with coal-based graphene oxide (CGO) as a multi-functional conductive binder to realize dual functional utilization of coal. As compared to traditional binder (CMC), electrodes with the CGO binder exhibits significantly increased reversible capacity and rate capability. This work provides a facile method for coal-based carbon materials used in SIBs.

Enzymolytic lignin derived Fe–N codoped porous carbon materials as catalysts for oxygen reduction reactions

Numerous active sites and hierarchical pore structures are important for improving catalytic performance for the oxygen reduction reaction (ORR). In this work, a series of iron-nitrogen-doped porous carbon materials (Fe–N–C) with ORR catalytic activity were prepared by a one-step pyrolysis method using enzymolytic lignin as the raw material, soy protein isolate and iron chloride as dopants. The results showed that the samples with the best performance have abundant Fe-Nx active sites and mesoporous structures. At the same time, the electrocatalytic results indicate that the half-wave potential of catalyst was 0.84 V, which reached 96.55% of commercial Pt/C catalysts (E1/2 = 0.86 V), it still preserves an initial current density of 92%, after 10,000 s of circulation, which is much better than Pt/C (86%). Due to the low cost, high activity and stable ORR property, the prepared non-precious metal electrocatalyst will play an important role in the applications of fuel cells.

Bifunctional ligand Co metal-organic framework derived heterostructured Co-based nanocomposites as oxygen electrocatalysts toward rechargeable zinc-air batteries

Rational construction of efficient and robust bifunctional oxygen electrocatalysts is key but challenging for the widespread application of rechargeable zinc-air batteries (ZABs). Herein, bifunctional ligand Co metal–organic frameworks were first explored to fabricate a hybrid of heterostructured CoOx/Co nanoparticles anchored on a carbon substrate rich in CoNx sites (CoOx/Co@CoNC) via a one-step pyrolysis method. Such a unique heterostructure provides abundant CoNx and CoOx/Co active sites to drive oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively. Besides, their positive synergies facilitate electron transfer and optimize charge/mass transportation. Consequently, the obtained CoOx/Co@CoNC exhibits a superior ORR activity with a higher half-wave potential of 0.88 V than Pt/C (0.83 V vs. RHE), and a comparable OER performance with an overpotential of 346 mV at 10 mA cm−2 to the commercial RuO2. The assembled ZAB using CoOx/Co@CoNC as a cathode catalyst displays a maximum power density of 168.4 mW cm−2, and excellent charge–discharge cyclability over 250 h at 5 mA cm−2. This work highlights the great potential of heterostructures in oxygen electrocatalysis and provides a new pathway for designing efficient bifunctional oxygen catalysts toward rechargeable ZABs.

Efficacy and Mechanism of Tetracycline Adsorption by Boron-doped Mesoporous Carbon

Using coconut shell and boric acid as raw materials， a new boron-doped coconut shell mesoporous carbon material （B-CSC） was prepared using a simple one-step pyrolysis method for efficient adsorption and removal of tetracycline pollutants in water. The effects of pyrolysis temperature and boron-carbon mass ratio on the adsorption performance under key preparation conditions were systematically studied， and their microstructure and physicochemical properties were characterized using a specific surface area and pore size analyzer （BET）， field emission scanning electron microscopy （SEM）， X-ray photon spectroscopy （XPS）， Raman spectrometer （Raman）， and Zeta potentiometer （Zeta）. The effects of initial pH， different metal cations， and different background water quality conditions on the adsorption effect were systematically investigated. Combined with material characterization and correlation analysis， the enhanced adsorption mechanism was discussed and analyzed in depth. The results showed that one-step pyrolysis could incorporate boron into the surface and crystal lattice of coconut shell charcoal， resulting in a larger specific surface area and pore volume， and the main forms of boron introduced were H3BO3， B2O3， B， and B4C. The adsorption capacity of B-CSC to tetracycline reached 297.65 mg·g-1， which was 8.9 times that of the original coconut shell mesoporous carbon （CSC）. At the same time， the adsorption capacity of B-CSC for rhodamine B （RhB）， bisphenol A（BPA）， and methylene blue （MB）， common pollutants in aquatic environments， was as high as 372.65， 255.24， and 147.82 mg·g-1， respectively. The adsorption process of B-CSC to tetracycline was dominated by physicochemical interaction， mainly involving liquid film diffusion， surface adsorption， mesoporous and microporous diffusion， and active site adsorption， and H3BO3 was the main adsorption site. The adsorption strengthening mechanism mainly reduced the chemical inertness of the carbon network and enhanced its π-π interaction and hydrogen bonding with tetracycline molecules.

A composite catalyst of sugarcane-derived N-doped biochar and Fe(NO3)3 for improved electron transfer in stepwise oxidation of 5-hydroxymethylfurfuran under air

Flexible catalysts for the efficient oxidation of 5-hydroxymethylfurfuran (HMF) into valuable chemicals are in urgent demand. In this contribution, the sugarcane-derived N-doped biochar (Su-NCs) was prepared by MgCl2 activation in the presence of urea via a one-step pyrolysis method, which constructed a composite catalyst with Fe(NO3)3 for HMF oxidation. The perfect combination of Su-NCs/Fe(NO3)3 revealed remarkably enhanced catalytic performance and HMF conversion of ca. 100.0% with a 92.0% total yield in air. The effects of specific N-doping sites on the catalytic activity and role of Fe3+ were explored. The results disclosed the electron-rich pyridine-N and Fe3+ synergistically implemented the stepwise oxidation of alcohol to aldehyde and then carboxylic acid. Importantly, the Fe2+ came from electron transfer between the electron-rich N-doped sites and Fe3+ was the origin of reactive oxygen species (∙O−2), which further determined the reactivity and product distributions. The ∙O−2was favorable for the oxidation of hydroxyl while the ∙OH evolved from ∙O−2 preferred to attack aldehyde on the furan ring. This work emphasizes the importance of surface electron transfer of Su-NCs on oxidation efficiency of HMF and creates an alternative chance to produce value-added chemicals from raw biomass.

Catkin-derived carbon microtubes for hybrid anode materials of high-performance lithium ion batteries

As a common biological waste, catkin shows negligible economic value and is hazardous to the environment and human respiratory health. To turn waste into treasure, in this work, a hybrid anode is successfully prepared by using the catkin-derived 1D hollow carbon microtube as dispersing agents to well disperse the MnO particles via a simple one-step pyrolysis method. Benefiting from the high electrical conductivity and hollow microtubule structure of the catkin-derived carbon, as well as the evenly dispersion of the MnO particles and the interfacial energy storage of Mn0/Li2O interfaces, the lithium ion battery based on the resultant MnO/C hybrid anode exhibits outstanding rate performance (high reversible specific capacity of 1365 mAh g−1 at a current density of 0.1 A g−1 and maintains 451 mAh g−1 even at a high current density of 6.4 A g−1) and superior cycling stability (retains ∼100 % after 1000 cycles at a current density of 0.8 A g−1). This work conforms to the development concept of green environmental protection and realizes the unity of economic and social benefits.

A graphitic C3N4 nanocomposite-based fluorescence platform for label-free analysis of trace mercury ions.

In this study, a nanocomposite consisting of graphitic carbon nitride nanosheets loaded with graphitic carbon nitride quantum dots (CNQDs/CNNNs) was synthesized via a one-step pyrolysis method. This nanocomposite exhibited excellent thermal stability, photobleaching and salt resistance. Then a new fluorescence sensing platform based on CNQDs/CNNNs was constructed, which showed high sensitivity and selectivity towards trace mercury ions (Hg2+). By using X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra and density functional theory, the fluorescence response mechanism was elucidated where Hg2+ could interact with CNQDs/CNNNs, causing a structural change in the nanocomposite, further affecting its bandgap structure, and finally leading to fluorescence quenching. The linear range for detecting Hg2+ was found to be 0.025-4.0 μmol L-1, with a detection limit of 7.82 nmol L-1. This strategy provided the advantages of a rapid response and a broad detection range, making it suitable for quantitative detection of Hg2+ in environmental water.

Electrolytic manganese residue-biochar composite for simultaneous removal of antimony and arsenic from water: Adsorption performance and mechanisms

Antimony (Sb) and arsenic (As) pollution in the water environment pose a threat to the ecological environment and human health. A lot of studies have been conducted on the removal of pollutants from water by modified biochar, but little attention has been paid to the simultaneous removal of Sb and As from water. This study aimed to simultaneously remediate the water contaminated by Sb and As and realize the resource utilization of solid waste. Herein, electrolytic manganese residue (EMR)-biochar composite (EB) was prepared by a one-step pyrolysis method using the mixture of EMR and distillers grains for the removal of As(III, V) and Sb(III, V) from water. The results indicated that the optimal pyrolysis temperature and EMR to distillers grains mass ratio for EB removal of As(III, V) and Sb(III, V) were 750 °C and 3∶1, respectively. The removal of As(III, V) and Sb(III, V) by EB was inhibited to varying degrees by HCO3−, PO43−, and humic acid. The maximum adsorption capacities of EB for As(III), As(V), Sb(III), and Sb(V) were 40.92, 40.54, 34.36, and 9.42 mg/g, respectively. The main adsorption mechanisms of As(III, V) and Sb(III, V) included complexation, hydrogen bonding, and pore filling. Compared with other engineered biochar composites, EB can be utilized not only as a potential adsorbent to treat water contaminated with As(III, V) and Sb(III, V), but also to enable the hazard-free treatment and resource utilization of EMR and distillers grains, achieving the goal of treating pollution with waste. Future studies on the remediation performance and mechanisms of EB for practical Sb and As co-contaminated soil and water are necessary.

Coaxial nickel cobalt selenide/nitrogen-doped carbon nanotube array as a three-dimensional self-supported electrode for electrochemical energy storage.

Herein, we propose a one-step urea pyrolysis method for preparing a nitrogen-doped carbon nanotube array grown on carbon fiber paper, which is demonstrated as a three-dimensional scaffold for constructing a nickel cobalt selenide-based coaxial array structure. Thanks to the large surface area, interconnected porous structure, high mass loading, as well as fast electron/ion transport pathway of the coaxial array structure, the nickel cobalt selenide/nitrogen-doped carbon nanotube electrode exhibits over 7 times higher areal capacity than that directly grown on carbon fiber paper, and better rate capability. The cell assembled by a nickel cobalt selenide/nitrogen-doped carbon nanotube positive electrode and an iron oxyhydroxide/nitrogen-doped carbon nanotube negative electrode delivers a volumetric capacity of up to 22.5 C cm-3 (6.2 mA h cm-3) at 4 mA cm-2 and retains around 86% of the initial capacity even after 10 000 cycles at 10 mA cm-2. A volumetric energy density of up to 4.9 mW h cm-3 and a maximum power density of 208.1 mW cm-3 are achieved, and is comparable to, if not better than, those of similar energy storage devices reported previously.

Preparation of Fe-BN-C catalysts derived from ZIF-8 and their performance in the oxygen reduction reaction.

Enhancing the oxygen reduction reaction (ORR) activity and stability of the fuel cell cathode electrocatalysts and reducing their costs are critical. In response to this need, Fe, B, and N co-doped hollow mesoporous carbon materials were prepared by a simple chemical doping one-step pyrolysis method using ZIF-8 as a precursor. The results showed that the optimized catalyst displayed a higher limiting current density (6.154 mA cm-2) and half-wave potential (0.859 V), which showed significant enhancement compared with the Pt/C catalyst (5.487 mA cm-2 and 0.853 V). Moreover, the optimized catalyst had outstanding long-term stability with a current density retention higher than 91% after 36 000 s of stability testing. This work provides a facile strategy for the design of outstanding ORR performance of non-precious metal oxygen reduction catalysts.

Highly Accessible Co-Nx Active Sites-Doped Carbon Framework with Uniformly Dispersed Cobalt Nanoparticles for the Oxygen Reduction Reaction in Alkaline and Neutral Electrolytes.

Porous carbon materials with nitrogen-coordinated transition metal active sites have been widely regarded as appealing alternatives to replace noble metal catalysts in oxygen-based electrochemical reaction activities. However, improving the electrocatalytic activity of transition-metal-based catalysts remains a challenge for widespread application in renewable devices. Herein, we use a simple one-step pyrolysis method to construct a Co nanoparticles/Co-Nx-decorated carbon framework catalyst with a near-total external surface structure and uniform dispersion nanoparticles, which displays promising catalytic activity and superior stability for oxygen reduction reactions in both alkaline and neutral electrolytes, as evidenced by the positive shift of half-wave potential by 44 and 11 mV compared to 20% Pt/C. Excellent electrochemical performance originates from highly accessible Co nanoparticles/Co-Nx active sites at the external surface structure (this is, exposing active sites). The thus-assembled liquid zinc-air battery using the synthesized electrocatalyst as the cathode material delivers a maximum power density of 178 mW cm-2 with an open circuit potential of 1.48 V and long-term discharge stability over 150 h.

Peroxymonosulfate activation by microplastics coagulated sludge-derived iron-carbon composite for effective degradation of tetracycline hydrochloride: Performance and mechanism

A simple one-step pyrolysis method was adopted to prepare microplastics (MPs) coagulated sludge into an iron-carbon composite (Fe-PSMPC), which was used to activate peroxymonosulfate (PMS) for the degradation of tetracycline hydrochloride (TC). The iron species in coagulated sludge were thermally reduced by carbon at 800 °C to produce abundant Fe0, which was successfully loaded on the surface of carbon derived from MPs. Then, the effects such as Fe-PSMPC dosage, PMS dosage, initial pH, and pollutant concentration on TC degradation were further investigated. The results showed that the Fe-PSMPC/PMS system was able to degrade TC effectively over a wide pH range. Under the optimal process conditions, the removal rate of TC could reach 87.5 % within 16 min. In addition, quenching experiments, electron paramagnetic resonance, electrochemical measurements, and X-ray photoelectron spectroscopy analyses indicated that the non-free radical (1O2 and electron transfer) pathway was dominant in the TC degradation system, and the free radical (•OH and SO4• −) pathway also showed significant contribution. Fe0 on Fe-PSMPC was the main active site, and the keto group (C = O) also acted as an active site to facilitate the generation of 1O2. Furthermore, three possible degradation pathways of TC were elaborated based on the 17 intermediates detected by liquid chromatography-mass spectrometry. This work provides an economical and convenient recycling strategy for the MPs coagulated sludge, which can be converted into an effective catalyst to activate PMS for the degradation of organic pollutants, thus realizing “treating waste with waste”.