Nitrogen-containing Functional Groups Research Articles

Tailoring the surface functional groups of biochar for enhanced adsorption and degradation of pharmaceutically active compounds

In this study, orange peel biochar (OPBC) was synthesized through a pyrolysis process. Decoration with two specific functional groups (i.e., –COOH and NH2) was performed through a ball milling-assisted modification process to yield the respective biochars (i.e., OPBC-COOH and OPBC-NH2). Both OPBC-COOH and OPBC-NH2 demonstrated excellent adsorption capacities for sulfamethoxazole (SMX) and carbamazepine (CBZ), and hydrogen bonding between the pharmaceuticals and BCs followed the primary adsorption mechanism. In addition, both OPBC-COOH and OPBC-NH2 (0.3 g/L) exhibited high degradation efficiencies for SMX (10 mg/L, 87 %; 92 %) and CBZ (10 mg/L, 73 %; 83 %) when peroxymonosulfate (PMS, 1 mM) was present. The scavenging experiments confirmed that electron transfer and radical/non-radical pathways (·OH and 1O2) are mainly responsible for the degradation of SMX and CBZ, respectively. It was also proven that the oxygen- and nitrogen-containing surface functional groups on BC are important for activating PMS for the degradation of organic pollutants. These findings provide new insights into the effects of functional groups on BC for the degradation of contaminants of emerging concern.

Enhanced activity and durability of Pt nanoclusters catalyst by using nitrogen-doped carbon layer coated carbon nanotubes as anchors and nanowires for ORR

Platinum-based catalysts remain the top choice for oxygen reduction reaction (ORR) in fuel cells. However, their activity and durability in the acidic medium are still under improvement. In this work, the Pt nanoclusters anchored the nitrogen-doped carbon nanotubes (Pt-NCNTs) have been synthesized by using a series process of pyrrole coating on the CNTs and subsequent pyrolysis to the chemical immersion reduction of Pt ions. The inner CNTs of Pt-NCNTs function as the nanowires offering a high-speed pathway for electron transport, and the Pt nanoclusters increases the active sites. The theoretical calculation demonstrates that the local structural defects and the uneven charge distribution induced by nitrogen-containing functional groups and porous structure are favorable to capture Pt ions for the nucleation of Pt nanoclusters. Compared with the commercial 40wt% Pt/C (0.94 and 0.80V), the Pt-NCNTs-1000 with Pt loading amount of 33.0wt% owns the more positive onset potential and half-wave potential of 0.97 and 0.81V in the sulfuric acid medium. Meanwhile, the strong attachment of Pt nanoclusters on the nitrogen-doped porous carbon layer results in a stable interface to effectively prevent the metallic species from migration and agglomeration during the electrode reactions. Therefore, the ORR current of Pt-NCNTs-1000 retained 84.3% of the initial value after 50000s operation superior to the commercial Pt/C (64.6%).

Innovative Approach to Chiral Polyurethanes: Asymmetric Copolymerization with Isocyanates.

The introduction of nitrogen-containing functional groups to chiral polymer backbones enables the tailoring of physical properties and offers opportunities for further post-polymerization modification. However, the substrate scope of such polymers is extremely limited because monomers having nitrogen-containing groups can change coordination state with respect to the metal centers, thus decreasing the activity and enantioselectivity and even poisoning the catalyst completely. In this paper, we report our attempts to carry out the asymmetric copolymerization of meso-epoxide with highly reactive isocyanates. In particular, we found that biphenol-linked bimetallic Co(III) complexes with multiple chiral centers are very efficient in catalyzing this asymmetric copolymerization reaction, affording optically active polyurethanes with a completely alternating nature and a high enantioselectivity of up to 94% ee. Crucially, we identified that the steric hindrance at the phenolate ortho position of the ligand strongly influences the catalytic activity and product enantioselectivity. In addition, density functional theory calculations revealed that the highly sterically bulky substituents change the mechanism from bimetallic to monometallic, and result in the unexpected inversion of the chiral induction direction. Moreover, the high stereoregularity of the produced polyurethanes enhances their thermal stability. This study offers a versatile methodology for the synthesis of chiral polymers containing nitrogen functionalities.

Construction of a food waste biochar model and determination of contaminant adsorption sites: Combining experimental characterisation with quantum chemical calculations

Increasing urbanization has made it a serious challenge to deal with food waste (FW) from people and wastewater with pollutants from industry. Biochar from FW pyrolysis(FWB) can be used as an adsorbent to adsorb pollutants from wastewater, but its molecular structure is still unknown, limiting the understanding of its adsorption mechanism and its application in industry. In this paper, a series of combined methods of experimental characterization and quantum chemical calculations, such as solid-state 13C nuclear magnetic resonance spectroscopy (13C NMR), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to investigate and successfully construct a model of the molecular structural features of FWB under the optimal contaminant adsorption preparation conditions. Based on the electrostatic potential distribution and adsorption experiments, the adsorption sites of the pollutants were elucidated. The results showed that the FWB prepared at different temperatures, 450 °C had a variety of oxygen-containing functional groups and polarity favorable for adsorption. In the molecular structure of FWB with the molecular formula C60H49N7O8, oxygen is present in the form of carboxyl, carbonyl, ether, alcohol hydroxyl, and phenol hydroxyl groups with numbers 1, 1, 1, 1, 2, 1, 2. Nitrogen is present in the form of pyridinyl nitrogen, pyrrolidinyl nitrogen, and primary amines with numbers 1, 1, and 5, respectively. In addition, nitrogen-containing and oxygen-containing functional groups are possible adsorption sites for pollutants on FWB, and alcohol hydroxyl and amino groups can bind better to Cu2+, which provides scientific guidance for improving the adsorption performance of biochar. This provides a solid foundation for the study of the microscopic adsorption mechanism of FWB and a method for the modeling of biochar from other biomasses.

Low-cost pyrolysis of biomass-derived nitrogen-doped porous carbon: Chlorella vulgaris replaces melamine as a nitrogen source.

Porous carbon generated from biomass has a rich pore structure, is inexpensive, and has a lot of promise for use as a carbon material for energy storage devices. In this work, nitrogen-doped porous carbon was prepared by co-pyrolysis using bagasse as the precursor and chlorella as the nitrogen source. ZnCl2 acts as both an activator and a nitrogen fixer during activation to generate pores and reduce nitrogen loss. The thermal weight loss experiments showed that the pyrolysis temperatures of bagasse and chlorella overlap, which created the possibility for the synthesis of nitrogen-rich biochar. The optimum sample (ZBC@C-5) possessed a surface area of 1508 m2g-1 with abundant nitrogen-containing functional groups. ZBC@C-5 in the three-electrode system exhibited 244.1F/g at 0.5A/g, which was extremely close to ZBC@M made with melamine as the nitrogen source. This provides new opportunities for the use of low-cost nitrogen sources. Furthermore, the devices exhibit better voltage retention (39%) and capacitance retention (96.3%). The goal of this research is to find a low cost, and effective method for creating nitrogen-doped porous carbon materials with better electrochemical performance for highly valuable applications using bagasse and chlorella.

Eco-friendly aqueous binder derived from waste ramie for high-performance Li-S battery

Even the sulfur cathode in lithium-sulfur (Li-S) battery has the advantages of high theoretical energy density, wide source of raw materials, no pollution to the environment, and so on. It still suffers the sore points of easy electrode collapse due to large volume expansion during charge and discharge and low active materials utilization caused by the severe shuttle effect of lithium polysulfides (LiPSs). Therefore, in this work, ramie gum (RG) was extracted from ramie fiber degumming liquid and used as the functional binder to address the above problems and improve the Li-S battery's performance for the first time. Surprisingly, the sulfur cathode using RG binder illustrates a high initial capacity of 1152.2 mAh/g, and a reversible capacity of 644.6 mAh/g after 500 cycles at 0.5 C, far better than the sulfur cathode using polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose (CMC) binder. More importantly, even if the active materials loading increased to as high as 4.30 mg/cm2, the area capacity is still around 3.1 mAh/cm2 after 200 cycles. Such excellent performances could be attributed to the abundant oxygen- and nitrogen-containing functional groups of RG that can effectively inhibit the shuttle effect of LiPSs, as well as the excellent viscosity and mechanical properties that can maintain electrode integrity during long-term charging/discharging. This work verifies the feasibility of RG as an eco-friendly and high-performance Li-S battery binder and provides a new idea for the utilization of agricultural biomass resources.

Engineering Nitrogen-Doped Carbon Quantum Dots: Tailoring Optical and Chemical Properties through Selection of Nitrogen Precursors.

The process of N-doping is frequently employed to enhance the properties of carbon quantum dots. However, the precise requirements for nitrogen precursors in producing high-quality N-doped carbon quantum dots (NCQDs) remain undefined. This research systematically examines the influence of various nitrogen dopants on the morphology, optical features, and band structure of NCQDs. The dots are synthesized using an efficient, eco- friendly, and rapid continuous hydrothermal flow technique. This method offers unparalleled control over synthesis and doping, while also eliminating convention-related issues. Citric acid is used as the carbon source, and urea, trizma base, beta-alanine, L-arginine, and EDTA are used as nitrogen sources. Notably, urea and trizma produced NCQDs with excitation-independent fluorescence, high quantum yields (up to 40%), and uniform dots with narrow particle size distributions. Density functional theory (DFT) and time-dependent DFT modelling established that defects and substituents within the graphitic structure have a more significant impact on the NCQDs' electronic structure than nitrogen-containing functional groups. Importantly, for the first time, this work demonstrates that the conventional approach of modelling single-layer structures is insufficient, but two layers suffice for replicating experimental data. This study, therefore, provides essential guidance on the selection of nitrogen precursors for NCQD customization for diverse applications.

Investigation of phenol adsorption performance and mechanism using Na2EDTA-modified activated biochars produced from a fluidized bed pyrolysis system

The study investigated the characteristics and mechanisms of phenol adsorption in three types of modified activated biochars (rice straw, rice husk, and sawdust) obtained through fluidized bed pyrolysis system, particularly focusing on biochars activated with KOH and modified with Na2EDTA. The experimental comprehensively analyzed the morphology of biochars through nitrogen adsorption-desorption (BET), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), while employed mathematical descriptions with isotherm, adsorption kinetics, and thermodynamics models. The adsorption process could be better described by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating the spontaneous and exothermic reaction. After being activated by KOH, results showed that KOH could generate potassium vapor for etching carbon layers at high temperatures, forming a microporous structure. With the KOH activation and Na2EDTA modification, the amino (-NH2) and carboxyl (-COOH) groups were effectively loaded on the adsorbents. Especially, after Na2EDTA modification, an N1s peak appeared in the XPS spectrum, the peak area ratios of pyrrolic-N and graphitic-N drop from 54.20 % to 21.45%–49.15% and 16.62%, while that of pyridinic-N and nitrogen oxides correspondingly increased, indicating the presence and alteration of nitrogen-containing functional groups, promoting the formation of π-π bonds, and strengthening of π-π dispersion effects. Meanwhile, the specific surface area reaches 1143.60 m2/g to 1337.20 m2/g, the maximum adsorption capacities reach 156.29 mg/g to 195.17 mg/g, which outperform the commercial activated biochars. This finding suggests that Na2EDTA -modified biochars by fluidized bed could enhance the adsorption capacity for phenol, and offer economic feasibility and high production technical for the environmental protection and wastewater treatment.

Efficient degradation of phenol in water by ball-milling modulated nitrogen-doped structured biochar

Presently, most kinds of biochar rely on the addition of transition metals to improve their electron transport capacity, thereby boosting the activation of oxidants. However, challenges such as the precipitation of transition metals and the chemical inertness of biochar are commonly encountered. Biochar with nitrogen-containing functional groups has emerged as a promising solution as oxidant activators. The nitrogen doping of biochar through ball milling is a straightforward, cost-effective, and efficient preparation method. To optimize the activation properties, a multi-step process involving roasting, ball milling, and tempering was employed to produce biochar. Sesame dregs was chosen as the precursor for this biochar. By optimizing the roasting temperature to 900 °C and using urea as the nitrogen source, biochar derived from sesame residue was successfully prepared. This biochar featured pyridine nitrogen as the primary functional group, exhibiting improved crystallinity and aromaticity. The activation of sodium persulfate (3.0 mM) with biochar eliminated phenol from wastewater with an initial concentration of 50 mg/L in just 15 minutes, achieving a remarkable mineralization rate of 96.77%. Even after undergoing six cycles of repeated use, the system consistently removed 97.73% of phenol within the same timeframe, maintaining a high mineralization rate of 86.77%. Notably, it was found that N-CN, N-6, and N-q were instrumental in stimulating reactive oxygen species (ROS), while ·OH, SO4·-, and 1O2 served as the primary ROS responsible for degrading phenol. The research also revealed a linear relationship between active oxygen sites and oxidized substances, offering insights into the mechanism of phenol degradation.

Efficient removal of U(VI) from aqueous solution using poly(amidoxime-hydroxamic acid) functionalized graphene oxide.

The efficient development of selective materials for uranium recovery from wastewater and seawater is crucial for the utilization of uranium resources and environmental protection. The potential of graphene oxide (GO) as an effective adsorbent for the removal of environmental contaminants has been extensively investigated. Further modification of the functional groups on the basal surface of GO can significantly enhance its adsorption performance. In this study, a novel poly(amidoxime-hydroxamic acid) functionalized graphene oxide (pAHA-GO) was synthesized via free radical polymerization followed by an oximation reaction, aiming to enhance its adsorption efficiency for U(VI). A variety of characterization techniques, including SEM, Raman spectroscopy, FT-IR, and XPS, were employed to demonstrate the successful decoration of amidoxime and hydroxamic acid functional groups onto GO. Meanwhile, the adsorption of U(VI) on pAHA-GO was studied as a function of contact time, adsorbent dosage, pH, ionic strength, initial U(VI) concentration, and interfering ions by batch-type experiments. The results indicated that the pAHA-GO exhibited excellent reuse capability, high stability, and anti-interference ability. Specially, the U(VI) adsorption reactions were consistent with pseudo-second-order and Langmuir isothermal adsorption models. The maximum U(VI) adsorption capacity was evaluated to be 178.7mg/g at pH 3.6, displaying a higher U(VI) removal efficiency compared with other GO-based adsorbents in similar conditions. Regeneration of pAHA-GO did not significantly influence the adsorption towards U(VI) for up to four sequential cycles. In addition, pAHA-GO demonstrated good adsorption capacity stability when it was immersed in HNO3 solution at different concentrations (0.1-1.0mol/L) for 72h. pAHA-GO was also found to have anti-interference ability for U(VI) adsorption in seawater with high salt content at near-neutral pH condition. In simulated seawater, the adsorption efficiency was above 94% for U(VI) across various initial concentrations. The comprehensive characterization results demonstrated the involvement of oxygen- and nitrogen-containing functional groups in pAHA-GO in the adsorption process of U(VI). Overall, these findings demonstrate the feasibility of the pAHA-GO composite used for the capture of U(VI) from aqueous solutions.

Integrating high-throughput phenotypic profiling and transcriptomic analyses to predict the hepatosteatosis effects induced by per- and polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) is a large compound class (n > 12,000) that is extensively present in food, drinking water, and aquatic environments. Reduced serum triglycerides and hepatosteatosis appear to be the common phenotypes for different PFAS chemicals. However, the hepatosteatosis potential of most PFAS chemicals remains largely unknown. This study aims to investigate PFAS-induced hepatosteatosis using in vitro high-throughput phenotype profiling (HTPP) and high-throughput transcriptomic (HTTr) data. We quantified the in vitro hepatosteatosis effects and mitochondrial damage using high-content imaging, curated the transcriptomic data from the Gene Expression Omnibus (GEO) database, and then calculated the point of departure (POD) values for HTPP phenotypes or HTTr transcripts, using the Bayesian benchmark dose modeling approach. Our results indicated that PFAS compounds with fully saturated C-F bonds, sulfur- and nitrogen-containing functional groups, and a fluorinated carbon chain length greater than 8 have the potential to produce biological effects consistent with hepatosteatosis. PFAS primarily induced hepatosteatosis via disturbance in lipid transport and storage. The potency rankings of PFAS compounds are highly concordant among in vitro HTPP, HTTr, and in vivo hepatosteatosis phenotypes (ρ = 0.60–0.73). In conclusion, integrating the information from in vitro HTPP and HTTr analyses can accurately project in vivo hepatosteatosis effects induced by PFAS compounds.

Simulation of the VOC Adsorption Mechanism on Activated Carbon Surface by Nitrogen-Containing Functional Groups

In this paper, the physical adsorption of volatile organic compounds (VOCs) such as methyl chloride (CH3Cl), carbon disulfide (CS2), dimethyl sulfide (C2H6S), and benzene (C6H6) by three models of activated carbon (without a functional group, with a pyridine-containing functional group, and with a pyrrole-containing functional group) was simulated. The surface electrostatic potential (ESP), physical adsorption energy, and non-covalent interaction between activated carbon and VOC molecules were analyzed based on the density functional theory (DFT). The effect mechanism of nitrogen-containing functional groups on VOC adsorption by activated carbon was determined. Our simulations showed that nitrogen-containing functional groups can change the surface ESP and polarity of activated carbon. The pyrrole functional group is conducive to CH3Cl and CS2 adsorption on the activated carbon plane, while the pyridine functional group is relatively small or even unfavorable for CH3Cl and CS2 adsorption on the activated carbon plane. The promotional effect of the pyrrole functional group on the adsorption of C2H6S is more significant than that of the pyridine functional group. The adsorption of C6H6 on activated carbon occurs through parallel-displaced π–π stacking interactions, in which functional groups have little influence on it. The adsorption energy of VOCs on the activated carbon plane is higher than that at the edge, so VOCs are more likely to be adsorbed on the activated carbon plane.

Machine-learning-aided prediction and engineering of nitrogen-containing functional groups of biochar derived from biomass pyrolysis

Biochar, derived through biomass pyrolysis, is an emerging carbonaceous material with significant potential in various applications. The performance of biochar in applications depends heavily on its surface characteristics, including its content of N-containing functional groups. In this study, machine learning (ML) was used for the prediction and engineering of biochar N-containing functional groups, specifically amine-N (N-A), pyrrolic-N (N-5), and pyridinic-N (N-6). The single-target random forest model accurately predicted N recovery in biochar (char-N yield) and N-A, N-5, and N-6 contents, achieving test R2 of 0.91–0.97. Model interpretations revealed that pyrolysis temperature was the most influential factor in predicting char-N yield, N-A, N-5, and N-6. The multi-target random forest model achieved an average test R2 of 0.93, and it was used to optimize pyrolysis parameters for designing biochar N-functional groups. This process was followed by experimental verification. Relative errors for the three N-containing functional groups were mostly within 15% (18.4% on average). The favorable results obtained from experimental verification demonstrate the significant potential of ML in biochar engineering.

Liquid-waste derived magnetic porous carbon sphere for effective removal of tetracycline from aqueous solution

Effective removal of tetracycline (TC) from wastewater is highly important while still faces challenges especially in adsorption capacity. Herein, a novel N-doped magnetic porous graphitic carbon sphere (N-MPGCS) adsorbent was fabricated by a green strategy using tannic acid (TA) as organic ligand and stainless steel pickling wastewater as metal source. Melamine was also introduced to increase nitrogen-containing functional groups. Among the obtained carbon spheres, N-MPGCS1–800 sample shows a large specific surface area (up to 922.78 m2 g−1), appropriate O/N functional groups, suitable sp2 carbon, and good magnetic responsivity. Benefiting from these merits, this optimal material exhibits a high Langmuir adsorption capacity (1005.5 mg g−1 at 45 °C) for TC, fast adsorption kinetics (5 min for adsorption equilibration time at 50 mg L−1), and good applicability towards pH (3−10) and co-existing ions. Besides, the excellent magnetism permits the convenient and rapid recovery of adsorbent from the adsorption system. Moreover, the high TC removal ratio (92.3% after three cycles) presents its outstanding regeneration. Adsorption studies and characterizations show that H-bond, π-π stacking, metal-organic complexation interactions, and pore-filling effect contribute to the adsorption together. In addition, N-MPGCS1–800 also shows good removal on enrofloxacin, moxifloxacin, and norfloxacin. This work proves that N-MPGCS material can serve as a potential adsorbent, and more importantly, it gives a new path for mining industrial waste to produce high-effective magnetic carbon materials.

Nitrogen enriched high specific surface area biomass porous carbon: A promising electrode material for supercapacitors

In this report, a hierarchical porous activated carbon material with interconnected micro-meso-macro pores was prepared and studied with biomass waste as the starting point and transformation into high-value materials as the destination. Based on biomass hazelnut shell, a porous carbon material with a large specific surface area (3374 m2 g−1), rich pore structure, and suitable nitrogen content is constructed with polypyrrole as nitrogen source and KOH as the activator. Because of its unique pore structure, large specific surface area, and suitable nitrogen content, the prepared material as supercapacitor electrodes showed excellent capacitive performance (334 F g−1 at 0.5 A g−1), good rate capacity, and cycle stability. The experimental results show that the introduced nitrogen-containing functional groups endow the material with large pseudo-capacitance, which is conducive to increasing the specific capacitance. In addition, the symmetrical supercapacitor devices assembled on the basis of the material also showed excellent performance with an energy density of 11.4 W h kg−1 at a power density of 300.4 W kg−1. This synthetic strategy shows that the preparation of high-value electrode materials from biomass waste is promising.

The influence of nitrogen-containing functional groups and pore structure on the adsorption of per- and polyfluoroalkyl substances in ultrapure and real water

Activated carbon adsorption has been identified as an effective technique for per- and polyfluoroalkyl substances (PFAS) removal. However, the role of nitrogen-containing functional groups and pore size on PFAS elimination is uncertain. Therefore, this study prepared a series of AC with different nitrogen groups and pore structures by thermal treatment with urea under different temperatures (denoted as AC400, AC600 and AC800). Their PFAS adsorption performance in ultrapure and real water were investigated to identify the contribution of different nitrogen groups and pore structures. The adsorption experiment indicated that the modified AC800 with high proportion of pyridine nitrogen and medium pore volume achieved the best performance in ultrapure water due to the electrostatic interaction. However, in the real water contained dissolved organic matter (DOM), rather than AC800, AC600 with large mesopore volume exhibited the maximum adsorption capacity and kinetic due to its better inhabitation of pore blockage by DOM. It could be inferred that the electrostatic attraction force was more important in PFAS adsorption in ultrapure water, but in real water the mesopore volume was more critical due to the pore blockage by DOM. This study can provide guidance and implications for selection and development of future PFAS adsorption carbon-based material.

The Effect of Nitrogen Functional Groups on Pb0, PbO, and PbCl2 Adsorption over a Carbonaceous Surface.

Lead (Pb) pollution, especially from the incineration of municipal solid waste (MSW), poses a significant threat to the environment. Among all the effective methods, activated carbon (AC) injection serves as an effective approach for lead removal from flue gas, while the modification of ACs emerges as a crucial pathway for enhancing Pb adsorption capacities. Density functional theory (DFT) is employed in this study to investigate the mechanisms underlying the enhanced adsorption of Pb species (Pb0, PbO, and PbCl2) on nitrogen-functionalized carbonaceous surfaces. The results show that nitrogen-containing groups substantially enhance lead adsorption capacity, with adsorption energies ranging from -526.18 to -288.31 kJ/mol on nitrogen-decorated carbonaceous surfaces, much higher than those on unmodified surfaces (-310.35 to -260.96 kJ/mol). Additionally, electrostatic potential and density-of-states analyses evidence that pyridinic nitrogen atoms remarkably expand charge distribution and strengthen orbital hybridization, thereby augmenting lead capture. This research elucidates the role of nitrogen-containing functional groups in lead adsorption, offering valuable insights for the development of highly efficient biomass-derived activated carbon sorbents for lead removal.

Performance of nitrogen-containing functional groups on SO2 adsorption by active coke

The main aim of this study is to investigate the mechanism of the effect of the nitrogen-containing functional group of activated coke on SO2 adsorption through experiments and simulations. In this work, active coke with rich pyrrole and pyridine groups was prepared by ammonia modification. It has been found that the presence of pyrrole and pyridine groups, which can increase the surface polarity of active coke and the strength of non-covalent interactions, favors SO2 adsorption. Simulations show that the adsorption energy and non-covalent interaction strength of SO2, H2O and O2 on the surface and edge of active coke models with pyrrole group are greater than those with pyridine group, except for the adsorption of H2O on the edge of active coke. The presence of H2O reduces the adsorption capacity of SO2, mainly due to the competitive adsorption between H2O and SO2. Experimental research shows that the presence of H2O increases the content of S element on the active coke surface after adsorption. So, H2O not only promotes the adsorption of SO2, but also competes with it. Compared to O2, H2O forms stronger hydrogen bonds and dipole–dipole interactions with SO2, which can promote the adsorption of SO2.

Preparation of nitrogen-doped activated carbon used for catalytic oxidation removal of H2S

In this study, nitrogen-doped modified activated carbons were synthesized for H2S removal from Zhuxi activated carbon and 4,4′-bipyridine as raw material and nitrogen source, respectively. The synthesis strategy was hydrothermal treatment and subsequent NH3 annealing, and the formation and conversion patterns of the different N configurations were investigated. When the annealing temperatures were 500 °C and 600 °C, N-5 account for the majority. As the annealing temperature increased, the proportion of N-6 gradually increased. After the temperature increased to 1000 °C, N-5 and N-6 were converted to N-Q to a certain degree, while the amount of nitrogen doping decreased significantly. The sample H160-0.2-800 exhibited excellent H2S removal with a high sulfur capacity of up to 206.89 mg/g, significantly higher than that of the original activated carbon ZX1200 (67.56 mg/g). The reason for this is that the micropores (Vmic = 0.5155 cm3/g) and specific surface area (SBET = 1369.5 m2/g) of the modified activated carbon are more developed than those of the original activated carbon. A high nitrogen content (3.14 wt%) and N-6 configuration proportion (73.56 %) are significant reasons for the excellent adsorption properties. The mechanism of the catalytic oxidation was investigated. The introduction of surface nitrogen-containing functional groups alkalizes the activated carbon surface, enhancing the adsorption and dissociation of H2S and O2 and facilitating the formation of sulfur radicals and elemental sulfur.

Self-nitrogen-doped carbon spheres assisted CeO2 composites as a bifunctional adsorbent/photocatalyst for CO2 photoreduction

It is rather essential to increase CO2 adsorption and improve separation efficiency of photoinduced carriers by solar-driven CO2 reduction. Herein, we proposed a facile approach to synthesize millimeter-sized polyacrylonitrile-based carbon spheres (PANACSs) as a bifunctional adsorbent and self-nitrogen-doped source under a mild condition, and then embeds the highly active CeO2 to construct a CeO2@PANACSs composite with strong adsorption capacity and high reduction activity. The involved XRD, XPS, SEM, N2 adsorption/desorption, CO2 adsorption, UV–vis DRS, EIS, PL and In situ FTIR spectra were characterized. Results suggested that the obtained PANACSs can act as a catalyst to drive the reduction of CO2 into CO under visible light irradiation. CeO2@PANACSs showed the highest performance of photocatalytic reduction of CO2 for 10 h (210.65 μmol·g−1), and the yield of CO evolution is approximately 1.83 times and 17.42 times higher than that of pristine CeO2 and PANACSs, respectively. We found that the existence of nitrogen-containing functional groups further promoted the adsorption and activation of CO2. Among them, pyridinic nitrogen and pyrrolic nitrogen can be used as adsorption and activation sites to accelerate the separation and transfer of e--h+. Furthermore, Ce4+ on the surface of CeO2 acts as an electron capture agent, which captures the electrons that are not transferred in time and reduces itself to Ce3+, and then the formed Ce3+ reduces the adsorbed CO2 to CO. Finally, the possible mechanism is proposed to depict the photocatalytic CO2 reduction over the CeO2@PANACSs. Our finding provides a noteworthy promising strategy to construct bifunctional composite photocatalysts for achieving the high-efficient CO2 adsorption and photoreduction to CO.