High Catalyst Research Articles

Development of a heterogenous catalyst FeWO4/Cu2S as peroxymonosulfate activator for effective sulfachloropyridazine elimination

This work successfully synthesized magnetic FeWO4/Cu2S through a facile method with efficient peroxymonosulfate (PMS) activation to eliminate sulfachloropyridazine (SCP) in water, in which 97.56% of SCP was removed in 30 min with activating only 0.2 mM PMS. Factors such as calcination temperature, the addition amount of WS2 in FeWO4/Cu2S, molar ratio of Cu/Fe in FeWO4/Cu2S, catalyst dosage, solution pH, inorganic anions and natural organic matters（NOM）were investigated. It was found that in FeWO4/Cu2S at 1:2 possessed the best catalytic performance for PMS. FeWO4/Cu2S performed well in a wide pH range (3–9) and the effect was better under acidic conditions. A high catalyst dosage could supply more catalytic active sites for PMS activation and encourage the production of reactive oxygen species. Anions (HCO3−and HPO42−) and NOM significantly inhibited SCP degradation, whereas Cl− had only a tiny inhibitory impact. In addition, H2PO4− and NO3− demonstrated duality in the degradation of SCP. The oxidation process was dominated by non free radical oxidation by 1O2 rather than free radicals oxidation by HO⋅ and SO4•−. Three SCP degradation pathways—SO2 extrusion, S-N bond cleavage and hydroxylation were proposed according to intermediate products analysis. The mechanism was found that the introduction of W improved the dual metals cycles of Fe3+/Fe2+ and Cu+/Cu2+ which could efficiently promote PMS activation. In addition, the magnetic FeWO4/Cu2S was easy to separate after reaction, which had great application potential in the water treatment.

Core-Shell Design of Metastable Phase Catalyst Enables Highly-Performance Selective Hydrogenation.

Highly selective semihydrogenation of alkynes to alkenes is a highly important reaction for catalytic industry. Developing non-noble metal based catalysts with platinum group metal-like activity and selectivity is extremely crucial yet challenging. Metastable phase catalysts provide a potential candidate to realize high activity, yet the control of selectivity remains an open question. Here, this work first reports a metastable phase core-shell: face-centered cubic (fcc) phase Ag (10 at%) core-metastable hexagonal closest packed (hcp) phase Ni (90 at%) shell catalyst, which represents high conversion rate, high selectivity, and remarkable universality for the semihydrogenation of phenylacetylene and its derivatives. More impressively, a turnover frequency (TOF) value of 8241.8 h-1 is achieved, much higher than those of stable phase catalysts and reported platinum group metal based catalysts. Mechanistic investigation reveals that the surface of hcp Ni becomes more oxidized due to electron transfer from hcp Ni shell to fcc Ag core, which decreases the adsorption capacity of styrene on the metastable phase Ni surface, thus preventing full hydrogenation. This work has gained crucial research significance for the design of high performance metastable phase catalysts.

Solution combustion synthesis of Ce-free high entropy fluorite oxides: Formation, oxygen vacancy and long-term thermal stability

High-entropy oxides have gained more attention in recent years due to their excellent performance. In this work, five new Ce-free high entropy fluorite oxides ((Zr0.2Ti0.2Y0.2Nd0.2Sc0.2)O2-δ, (Zr0.2Ti0.2Y0.2La0.2Sc0.2)O2-δ, (Zr0.2Ti0.2La0.2Nd0.2Sc0.2)O2-δ, (Zr0.2Ti0.2Y0.2Nd0.2La0.2)O2-δ and (Zr0.2Ti0.2Dy0.2Nd0.2La0.2)O2-δ) were successfully synthesized by solution combustion synthesis with glycine as fuel. Their formation, oxygen vacancy, and long-term thermal stability were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. XRD results show that single fluorite phase was observed in (Zr0.2Ti0.2Y0.2La0.2Sc0.2)O2-δ, (Zr0.2Ti0.2Y0.2Nd0.2La0.2)O2-δ and (Zr0.2Ti0.2Dy0.2Nd0.2La0.2)O2-δ samples when sintering at 300, 600 and 900 °C, respectively, but (Zr0.2Ti0.2Y0.2Nd0.2Sc0.2)O2-δ sample with single-phase fluorite structure can only obtain by sintering at 900 °C and 1200 °C. For (Zr0.2Ti0.2La0.2Nd0.2Sc0.2)O2-δ sample, single fluorite phase can be obtained at 300 °C using calculated fuel and at 900 °C with using excess fuel. In addition, all the samples may have lower crystallinity due to excess glycine. XPS results indicate that factors of sintering temperature, fuel ratio and cationic radii strongly affect the generation of oxygen vacancy, especially for the sintering temperature. Morphology of the high entropy fluorite oxides presents in sponge-like microstructure. Superior long-term stability at high temperature was found in samples (Zr0.2Ti0.2Y0.2Nd0.2Sc0.2)O2-δ and (Zr0.2Ti0.2Y0.2Nd0.2La0.2)O2-δ. The findings in this work may have great potential applications in oxygen-deficient catalyst and high temperature catalyst.

Obtaining target dietary fats in the technology of step-by-step hydrogenation and their use

Introduction: Fats are an important component of a number of food products and affect their consistency, shelf life, taste, and nutritional qualities. Step-by-step hydrogenation is one of the main methods of modifying dietary fats, which allows for influencing their chemical structure and properties. The purpose of this study was to establish the main approaches to the step-by-step hydrogenation of dietary fats, the problems of the method, the main areas of use, and prospects for improving the technology. Material and Methods: A search to identify relevant papers was conducted for sources using open electronic databases, such as Google Scholar, Scopus, and Web of Science. Results and Discussion: During the study, the most common conditions of the hydrogenation reaction were established. The most important characteristics of the catalyst were determined by the activity, durability, selectivity, and stability of the formation of isomers. The formation of trans isomers of fatty acids, which reduces the quality of fat, has been identified as the main disadvantage of step-by-step hydrogenation. Factors contributing to the formation of trans isomers included high temperature, catalyst properties, and high content of unsaturated fatty acids in the feedstock. Step-by-step hydrogenation was identified to be the most characteristic of the soybean industry and for the production of confectionery and baking fats with specified properties. Conclusion: The results obtained indicate the potential of step-by-step hydrogenation to produce edible fats with a certain melting point and organoleptic characteristics after solving the cis/trans-isomerisation problem.

Curing Behavior of Sucrose with p-Toluenesulfonic Acid.

With respect to the fossil resources shortage, the development of bio-based wood adhesives is an important research topic in wood science. There has been research on using sucrose for bio-based adhesives. However, a high acid catalyst content and a high hot-pressing temperature are required when manufacturing particleboards. In this study, to explore the possibility of p-toluenesulfonic acid (PTSA) as a promising acid catalyst for sucrose-based adhesives, the curing behavior of sucrose with PTSA (Suc-PTSA) was clarified. The thermal analysis results showed that the thermal properties of sucrose decreased significantly with the addition of PTSA. Based on the results of the insoluble matter rate, the optimal mixture ratio and heating conditions were determined to be 95:5 and 180 °C for 10 min, respectively. According to the results of FT-IR, the heat-treated Suc-PTSA contained furan compounds. In the context of the dynamic viscoelasticity, the onset temperature at which the storage modulus (E') begins to rise was significantly lower than those of the other sucrose-based adhesives. PTSA has the potential to cure sucrose more efficiently and at lower temperatures than previous sucrose-based adhesives, making it a promising acid catalyst for sucrose.

Enhanced dry reforming of methane over NixCoy-HAP catalysts: Insights into the effect of Co species on carbon deposition and RWGS

Co and Ni are widely used to prepare bimetallic catalysts for dry reforming of methane (DRM) due to their comparable electronic configurations. In this study, a series of NixCoy-HAP catalysts were prepared, and by combining the characterization with XRD, H2-TPR, XPS, and TEM, the influence of Co incorporation on the redox properties, catalytic activity, catalytic stability, carbon deposition resistance and side reactions of the catalysts was evaluated. The results showed that both Ni and Co are homogeneously dispersed in the HAP structure by ion-exchange. The addition of Co enhances the reducibility of NixCoy-HAP and significantly improves the catalytic activity in the initial stage. Ni5Co1-HAP exhibits best catalytic stability in a 100-h long-term reaction accompanied by the deactivation of CH4 and CO2 with only 0.09% h−1 and 0.10% h−1, respectively. Characterization of the spent catalysts demonstrates that the decrease in activity of high Co content catalysts (Ni1Co5-HAP and Ni1Co10-HAP) is not due to carbon deposition, but rather that the addition of Co facilitates the RWGS side reaction. Process characterization of the catalysts in the CH4 one-component reaction indicates that an increase in the concentrates of one promotes a faster reduction of the other metal due to the strong electronic coupling of Ni and Co. These insights revealed here can pave the way for the preparation of Ni–Co bimetallic catalysts with high catalytic activity, robust resistance to carbon deposition and inhibition of a RWGS side reaction.

From the Glovebox to the Benchtop: Air-Stable High Performance Molybdenum Alkylidyne Catalysts for Alkyne Metathesis.

Molybdenum alkylidynes endowed with tripodal silanolate ligands belong to the most active and selective catalysts for alkyne metathesis known to date. This paper describes a new generation that is distinguished by an unprecedented level of stability and practicality without sacrificing the chemical virtues of their predecessors. Specifically, pyridine adducts of type 16 are easy to make on gram scale, can be routinely weighed and handled in air, and stay intact for many months outside the glovebox. When dissolved in toluene, however, spontaneous dissociation of the stabilizing pyridine ligand releases an active species of excellent performance and functional group tolerance. Specifically, a host of polar and apolar groups, various protic sites, and numerous basic functionalities proved compatible. The catalysts are characterized by crystallographic and spectroscopic means, including 95Mo NMR; their activity and stability are benchmarked in detail, and the enabling properties are illustrated by advanced applications to natural product synthesis. For the favorable overall application profile and ease of handling, complexes of this new series are expected to replace earlier catalyst generations and help encourage a more regular use of alkyne metathesis in general.

Analysis of the high‐pressure steam import behaviour of an integrated ethylene oxide/ethylene glycol petrochemical plant under different production scenarios

AbstractIntegrated ethylene oxide/ethylene glycols (EO/EG) plants are prominent energy consumers in the petrochemical sector, particularly concerning high‐pressure steam (HPS) usage which holds the potential for substantial energy savings. This study focuses on an unexplored territory: Examining the impact of EO catalyst type, selectivity, and glycols production capacity on HPS import in a plant in the Pars Special Economic Energy Zone (PSEEZ). Utilizing Python3 for data preprocessing and ordinary least squares linear regression analysis, we evaluate how varying catalyst loads and production scenarios influence HPS import. Regression models are created, encompassing normal and efficient HPS import scenarios, yielding positive outcomes in terms of correlation, mean error percentage, and R2 analysis. Comparing normal and efficient HPS import models highlights potential savings, uncovering opportunities to conserve between 45 and over 200 tonnes per day of HPS. We also explore the plant's HPS behaviour under 1% selectivity and production capacity reductions. Notably, catalyst activity decline markedly escalates HPS import for hybrid catalysts, while selectivity decline decreases HPS import for high‐activity catalysts. The models demonstrate that HPS import is ~150 tonnes per day more sensitive to a 1% change in selectivity compared to production capacity. Moreover, when comparing high activity and hybrid catalyst scenarios in normal and efficient cases, the most substantial HPS import difference arises under conditions of low selectivity, amounting to nearly 200 tonnes per day. Our methodology applies to other EO/EG plants. It is incorporated into our plant's energy management system, enabling continuous monitoring of steam import behaviour relative to catalyst and plant performance.

High Lewis acidity catalyst for direct depolymerization of microcrystalline cellulose to 5- hydroxymethylfurfural: Reaction optimization by central composite design

In direct conversion process of cellulose to 5-hydroxymethylfurfural (5-HMF), undesirable degradation inevitably occurs in the presence of Brønsted acid. Here, a carbonaceous catalyst was synthesized by grafting phosphotungstic acid to directly depolymerize microcrystalline cellulose (MCC) to 5-HMF. This catalyst exhibits high Lewis acidity (43.10 μmol g⁻1) and low Brønsted acidity (4.15 μmol g⁻1) with pyridine as reference compound. To comprehensively analyze the factors affecting MCC depolymerization, central composite design and response surface methodology techniques, incorporating variables such as reaction time, reaction temperature, catalyst dosage and MCC dosage. The highest yield of 5-HMF, 5.88 %, was obtained after 4.90 h at 171 °C using 45 mg of catalyst and 50 mg of MCC in biphasic system consisting of 1-butyl-3-methylimidazole chloride ([BMIM]Cl) and 2-sec-butylphenol. The catalyst was easily recovered and reused five times without a significant loss of catalytic activity. This work highlights the promise of efficient biomass refining by synergizing catalysts with high Lewis acidity and low Brønsted acidity in the biphasic system.

The performance improvement method of g-C3N4 based catalyst for hydrogen production from ammonia borane: A DFT investigation

In the study, based on the purpose of efficient catalytic AB for hydrogen production, the photochemical properties influence of metal(Ru, Ni) and nonmetal(B,P) elements doping on the g-C3N4 are studied systematacially. The design method of high performance bifunctional catalyst of photocatalysis and metal catalysis are provided. The results have proved that both non-metals B, P and metal Ru, Ni have an efficient regulatory effect on the band structure of g-C3N4, which make the band gap of the clean monolayer g-C3N4(001) decrease from 1.175 eV to 0.261eV(B-g-C3N4(001)) and 0.671eV(P-g-C3N4(001)), 0.164 eV(Ni-g-C3N4(001)) and 0.260 eV(Ru-g-C3N4(001)), respectively. B element have the better modification effect compared with the P element. The reduction of band gap is attributed to the electronic orbit modification effect of impurity element B, P, Ni, Ru in g-C3N4. Ru metal doped g-C3N4 is reduces the barrier of OH bond breakage of CH3OH(reduced from 4.551 eV to 1.530 eV), which is beneficial to the hydrogen-producing reaction of AB alcoholysis. The construction and design of a new bifunctional catalyst(photocatalysis and metal catalysis) RuNiB@g-C3N4 is an efficient route in catalyze AB for hydrogen production. The process of molecule NH3BH3, CH3OH and H2O adsorbed on the B-g-C3N4 are exothermic process, the adsorption energy are -1.562 eV, -1.392 eV and -1.443 eV, respectively. AB is preferentially adsorbed on the B-g-C3N4 catalyst, increasing the adsorption energy of CH3OH and H2O on B-g-C3N4-based catalysts is beneficial to the hydrogen production from AB. The study provides a theoretical method for the research on the technology of the coupling of metal catalysis/photocatalysis ammonia borane to produce hydrogen.

An effective, recyclable, eco-friendly 3-(2-aminoethyl)-1-methyl-1H-imidazol-3-ium bromide [Aemim]Br: Solvent, base free synthesis of carbonyl compound catalyst by FeCl3/TEMPO

We first report a novel solvent, base free synthesis of carbonyl compound catalyst by FeCl3/TEMPO at 40 °C with high-rate. In this article, we examine the mechanism of this catalytic system and compare the reactivity of aromatic alcohols. Furthermore, the efficacy of 3-(2-aminoethyl)-1-methyl-1H-imidazol-3-ium bromide [Aemim]Br could be maintained after seven recycling cycles. High catalyst productivity and reaction rate (5.53 to 22.50) have been accomplished with the use of an enhanced procedure.

2D ZIF-L arrays supported on zinc foam to activate peroxymonosulfate for degrading sulfamethoxazole through both radical and non-radical pathways

The development of easy recovery and high efficiency heterogeneous catalysts for activating peroxymonosulfate (PMS) is of great significance in the treatment of environmental pollutants. In this study, we successfully immobilized 2D ZIF-L arrays on a zinc foam (ZF) through a room temperature deposition method, creating a self-supporting ZIF-L/ZF catalyst. The ZIF-L/ZF exhibited high catalytic efficiency and durable recyclability for activating PMS to degrade sulfamethoxazole (SMX). Within 10 min, a 97 % degradation efficiency of SMX was achieved, which could be attributed to the unique integrated architecture and Co2+/Co3+ redox cycle of the catalyst. Furthermore, the effects of various environmental factors on catalytic activity were evaluated. By identifying the reactive species, both radical and non-radical oxidation process occurred during PMS activation. Additionally, the ZIF-L/ZF could be easy reused over 10 cycles, demonstrating a practical application value. We also proposed a possible degradation pathway for SMX based on Fukui index calculations and HPLC-MS. Our findings provide valuable insights into the construction of self-supporting catalyst for pollutant removal.

Multiple active sites for glucose conversion identified in Sn-Beta catalysts by CPMG MAS NMR and operando UV-Vis spectroscopy

Sn-Beta is an emerging heterogeneous zeolite catalyst that displays high activity for the catalytic conversion of glucose to desirable bio-based chemicals. Due to its promising catalytic properties, the synthesis and characterisation of Sn-Beta catalysts of different composition and preparation method have been the subject of a great number of studies. However, development of structure-activity-lifetime relationships for glucose conversion chemistry has been obstructed by several challenges, making the tailored preparation of high performance Sn-Beta catalysts harder to achieve. In this manuscript, we undertake continuous kinetic studies of four different Sn-Beta catalysts for glucose conversion, and pair the kinetic insights obtained with operando UV-Vis spectroscopy and quantitative 119Sn CPMG MAS NMR. In doing so, we reveal that at least two types of Sn species that are active for glucose conversion can exist in Sn-Beta catalysts, but that the two Sn species exhibit different levels of activity, selectivity and stability. In particular, we find that a Sn species resonating at − 690 ppm is characterised by high activity and is primarily selective towards the isomerisation of glucose to fructose, whereas a second Sn species resonating at − 658 ppm is characterised by lower activity for glucose conversion, and preferential selectivity towards alkylation and β-dehydration. Our studies also demonstrate that both Sn sites also possess different levels of stability during continuous operation. Consequently, we reveal that it is the ratio amongst these species that governs the overall catalytic performances of Sn-Beta catalysts for biomass conversion processes.

Heterogeneous Cu incorporated into Ni6Fe2-LDH/rGO induces spin exchange interaction to enhance alkaline hydrogen evolution

The efficiency of hydrogen evolution reaction (HER) takes an important influence on electrochemical water electrolysis, yet it still delivers sluggish kinetics mainly due to the high kinetic energy barriers. Herein, Cu1Ni5Fe2-Layered double hydroxides/reduced graphene oxide (denoted as Cu1Ni5Fe2-LDHs/rGO) with heterogeneous Cu atoms incorporated into Ni6Fe2-LDHs/rGO is constructed through a hydrothermal method and doping strategy in this works, wherein the subtle lattice distortion is availably regulated and optimized by Cu2+ Jahn-Teller effect, offering more active sites for HER. As benefits of the subtle lattice distortion and the spin exchange interaction, Cu1Ni5Fe2-LDHs/rGO displays ferromagnetism at room temperature and shows superior alkaline HER properties with a relatively low overpotentials of 50 mV at 10 mA cm−2 in 1.0 M KOH. The low Tafel slope of 38 mV dec−1 implies Cu1Ni5Fe2-LDHs/rGO owns an ultra-fast HER kinetic. This study can offer a new strategy to construct high efficient HER catalysts based on transition metal NiFe-LDHs.

Green lignocellulosic superadsorbent for superior Pd(II) removal and cascade catalytic conversion

In this study, a lignocellulosic-based adsorbent with excellent adsorption capacity for palladium and can be used for upcycling as an eco-friendly catalyst was prepared. The palladium adsorption performance of the lignocellulosic-based adsorption material was improved by 6 times compared to that of kraft lignin before the cationization modification process using polyethyleneimine. The prepared cationized lignin was introduced into a cellulose dissolution-regeneration process to be fabricated into a bead-type adsorbent, and through a cross-linking reaction using citric acid, a natural cross-linking agent, structural stability in contaminated water was achieved and adsorbent recovery and reuse were facilitated. As a result of the adsorption isothermal study, the maximum monolayer adsorption capacity for palladium of the regenerated cellulose beads containing cationized lignin was 212.5 mg/g. Palladium was recovered and reused from the beads by reducing Pd(II) to Pd(0) using the cationized lignin-containing regenerated cellulose beads as the catalyst. After reduction, Pd(0) present on and inside the beads successfully promoted the hydrogenation reaction that reduces 4-nitrophenol to 4-aminophenol with a conversion rate of 98 %. In addition, when reused 5 times after a simple water washing process, a conversion rate of 96 % or more was maintained, and high reuse catalyst efficiency was exhibited.

Design of active phase structure with high activity and stability in residue hydrotreating reactions

The catalyst with well-dispersed (Ni)MoS2 active phase characteristic of short slab length and low stacking numbers was designed by strengthening metal-support interaction (MSI) and metal dispersion, which displayed high activity and long-term stability in real-life residue hydrodesulfurization (HDS) reactions. Furthermore, the impacts of pseudo-boehmite and catalyst calcination temperature on surface properties were thoroughly investigated. Mo equilibrium adsorption method, Al27 NMR, XRD, Raman, UV–Vis DRS, and H2-TPR characterization showed that the hydroxyl groups concentration and tetrahedral cation vacancies increased upon reducing the pseudo-boehmite extrudates calcination temperature. Increasing calcination temperature of the catalysts further strengthened MSI, resulted in well-dispersed Mo species with enhanced MSI. Therefore, well-dispersed (Ni)MoS2 active phase was acquired on novel designed catalyst. XPS coupled with HRTEM indicated that the more potential active sites, less propensity for active phase evolution and gradual increase in sulfidation degree with processing time contributed to the high HDS performance of the designed active phase. This work can deepen our understanding toward evolution pattern of active phase during residue HDS catalysts, and give guidance for developing high performance catalyst by strengthening MSI and enhancing metal dispersion.

Interfacial electronic structure modulation enables PdAg/NiOx an advanced oxygen evolution electrocatalyst

Hydrogen production by electrolysis of water is one of the solutions to energy problems and environmental pollution. The design of efficient oxygen evolution electrocatalyst remains a challenging. One way to improve catalytic performance is to change the morphology and structure of the catalyst. Herein, a two-dimensional (2D) flake nano-flower heterostructured catalyst was designed on nickel foam (NF) substrate by simple hydrothermal and thermal annealing reactions. Benefiting from the porous nanosheet structure and synergistic effect between PdAg and NiOx, which facilitates electrolyte transport, the PdAg/NiOx nanosheets deliver a low overpotential (253 mV @ 10 mA cm−2) for oxygen evolution reaction (OER) and has excellent stability. In addition, the addition of PdAg alloy regulates the electronic structure of the active component Ni, which also makes for further improving the electrocatalytic OER performance. This work not only offers a promising strategy of in situ anchoring PdAg alloy on NiOx nanosheet but also provide a new way for the application of alloy heterogeneous interfaces to high performance OER catalysts.

Reduction and precipitation of chromium(VI) using a palladized membrane biofilm reactor

H2-driven reduction of hexavalent chromium (Cr(VI)) using precious-metal catalysts is promising, but its implementation in water treatment has been restricted by poor H2-transfer efficiency and high catalyst loss. We investigated the reduction of Cr(VI) through hydrogenation catalyzed by elemental-palladium nanoparticles (PdNPs) generated in-situ within biofilm of a membrane biofilm reactor (MBfR), creating a Pd-MBfR. Experiments were conducted using a Pd-MBfR and a non-Pd MBfR. The Pd-MBfR achieved Cr(VI) (1000 μg L−1) reduction of >99% and reduced the concentration of total Cr to below 50 μg L−1, much lower than the total Cr concentration in the non-Pd MBfR effluent (290 μg L−1). The Pd-MBfR also had a lower concentration of dissolved organic compounds compared to the non-Pd MBfR, which minimized the formation of soluble organo-Cr(III) complexes and promoted precipitation of Cr(OH)3. Solid-state characterizations documented deposition of Cr(OH)3 as the product of Cr(VI) reduction in the Pd-MBfR. Metagenomic analyses revealed that the addition and reduction of Cr(VI) had minimal impact on the microbial community (dominated by Dechloromonas) and functional genes in the biofilm of the Pd-MBfR, since the PdNP-catalyzed reduction process was rapid. This study documented efficient Cr(VI) reduction and precipitation of Cr(OH)3 by the Pd-MBfR technology.

Facile synthesis of single‐nickel‐atomic dispersed mesoporous carbon nanosheets with controllable nitrogen doping for efficient electrochemical CO2 reduction

AbstractThe catalytic conversion of CO2 into high value‐added chemical products driven by electricity was an effective strategy to reduce atmospheric CO2 concentration. The development of high efficiency catalysts had always been the core for electrocatalytic reduction of CO2. The single transition metal sites anchored on nitrogen‐doped carbon showed great potential in CO2 reduction reaction (CO2RR). In this paper, the atomically dispersed Ni−N sites are constructed on the two‐dimensional mesoporous carbon nanosheets by the secondary pyrolysis method. The rich mesoporous structure of the two‐dimensional nanosheets is beneficial to CO2 diffusion and adsorption during CO2RR, and the high nitrogen contents could increase the Ni single atom loadings. The nitrogen content and type could be controlled by regulating the ratio of nitrogen source to carbon source, and the catalyst activity is improved as the proportion of nitrogen sources increases. When the ratio of nitrogen source to carbon source is four, the oxidation state of Ni single atoms Ni@NMCN4 is between 0 and +2, and Ni single atoms exists as Ni−N4 structure with pyridinic N of 32.78 %, which exhibits the best electrochemical CO2RR activity. The active site of Ni@NMCN4 is confirmed as the highly stable Ni single atoms. Moreover, the pyridinic N species are proved to play an important role in enhancing the CO2 electroreduction performance. This work provides a new perspective to adjust the nitrogen content and type in transition metal monatomic‐N‐doped carbon electrocatalysts for CO2RR.

In situ Growth of Zeolite Imidazole Frameworks (ZIF-67) on Carbon Cloth for the Application of Oxygen Reduction Reactions and Microbial Fuel Cells.

Developing high surface area catalysts is an effective strategy to enhance the oxygen reduction reaction (ORR) in the application of microbial fuel cells (MFCs). This can be achieved by developing a catalyst based on metal-organic frameworks (MOFs) because they offer a porous active site for ORR. In this work, a novel in situ growth of 2D shell nanowires of ZIF-67 as a template for N-doped carbon (Co/NC) via a carbonization route was developed to enhance the ORR performance. The effects of different reaction times and different annealing temperatures were studied for a better ORR activity. The growth of the MOF template on the carbon cloth was confirmed using scanning electron microscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared. The Co/NC-800 exhibited an enhancement in the ORR activity as evidenced by an onset potential and half-wave potential of 0.0 vs V Ag/AgCl and -0.1 vs V Ag/AgCl, respectively, with a limited current density exceeding the commercial Pt/C. Operating Co/NC-800 on MFC revealed a maximum power density of 30 ± 2.5 mW/m2, a maximum current density of 180 ± 2.5 mA/m2.