Pyrrolic Nitrogen Research Articles

Biochar–goethite composites inhibited/enhanced degradation of triphenyl phosphate by activating persulfate: Insights on the mechanism

In this study, the biochar–goethite composites (MBC@FH) were synthesized through co–ball milling and the degradation of triphenyl phosphate (TPhP) was compared in persulfate (PDS) alone system and MBC@FH&PDS systems. The results showed that TPhP can be effectively degraded in PDS alone system and degradation efficiency reached up to 90 % within reaction of 8 h, at a PDS concentration of 10 mM, a reaction temperature of 30 °C and a system pH of 6.12. The obvious degradation can be ascribed to the reactive oxygen species (ROS) generated by self–decompose of PDS, among which 1O2, ∙OH and O2∙− play a major role in the degradation process. Although 350 °C biochar–goethite composites (MBC35@FH) and 800 °C biochar–goethite composites (MBC80@FH) facilitated PDS activation to produce more ROS, the catalytic degradation of TPhP was different in their systems. The degradation of TPhP was inhibited by MBC35@FH due to its stronger adsorption for TPhP, while MBC80@FH promoted TPhP degradation and degradation efficiency was up to 100 % within 6 h. 1O2 and SO4∙− played a stronger degradation role than ∙OH and O2∙− in above systems. The transformation of Fe species, functional groups (oxygen–containing functional groups, pyrrolic nitrogen) and persistent free radicals (PFRs) on the MBC@FH were involved in the PDS activation to produce ROS. Furthermore, MBC80@FH was more capable of activating PDS than MBC35@FH due to its abundant defect sites, larger specific surface area, more PFRs, higher Fe content and stronger electron transfer capability. In addition, seven possible TPhP intermediates were identified and possible degradation pathways of TPhP were proposed accordingly. This study illustrated that not all metallic carbon catalysts are necessarily beneficial for organic contaminants degradation.

Synthesis, Structure, and Optical Properties of a Bis-Macrocycle Derived from a Highly Emissive 1,3,6,8-Tetra(1H-pyrrol-2-yl)pyrene.

A tetra-functionalized pyrene precursor 4b is prepared using the Suzuki-Miyaura coupling of 1,3,6,8-tetrabromopyrene with N-Boc-2-pyrroleboronic acid. 4b displayed a blue emission with a high quantum yield (ϕF = 0.89). 4b is subjected to [3 + 2] Lewis acid-catalyzed condensation with 2,2'-bithiophene-dialcohol 5, affording a planar bis-N2S2 internally linked with pyrene. The single-crystal X-ray structure of bis-N2S2 revealed a planar conformation with all of the pyrrolic nitrogens and thiophenic sulfurs pointing toward the macrocyclic core. Further, the reduction of bis-N2S2 was attempted in the presence of Zn/NH4Cl at room temperature in CHCl3. A sharp color change from pink to brown was observed presumably due to the formation of its reduced congener bis-N2S2-2H. However, the reduced species was found to revert back to its oxidized form over a period of 25 min in CHCl3. Density functional theory (DFT) studies reveal that the two monocyclic halves of bis-N2S2-2H exhibit differences in aromaticity depending on amino and imino pyrroles present inside each individual core. Such a conversion was also monitored by ultraviolet-visible (UV-vis) absorption spectral studies, and the exact composition of bis-N2S2-2H was confirmed by High-resolution/mass spectrometry (HR/MS) analysis. Experimental and theoretical studies reveal a weak aromatic character of bis-N2S2 due to the absence of global conjugation.

Rational Design of Carbon-Based Porous Aerogels with Nitrogen Defects and Dedicated Interfacial Structures toward Highly Efficient CO2 Greenhouse Gas Capture and Separation.

CO2 capture from flowing flue gases through adsorption technology is essential to reduce the emission of CO2 to the atmosphere. The rational design of highly efficient carbon-based absorbents with interfacial structures containing interconnected porous structures and abundant adsorption sites might be one of the promising strategies. Here, we report the synthesis of nitrogen-doped carbon aerogels (NCAs) via prepolymerized phenol-melamine-formaldehyde organic aerogels (PMF) by controlling the addition amount of ZnCl2 and the precursor M/P ratio. It has been revealed that NCAs with a higher specific surface area and interconnected porous structures contain a large amount of pyridinic nitrogen and pyrrolic nitrogen. These would act as the intrinsic adsorption sites for highly effective CO2 capture and further improve the CO2/N2 separation efficiencies. Among the prepared samples, NCA-1-2 with a high micropore surface area and high nitrogen content exhibits a high CO2 adsorption capacity (4.30 mmol g-1 at 0 °C and 1 bar) and CO2/N2 selectivity (36.5 at 25 °C, IAST). Under typical flue gas conditions (25 °C and 1.01 bar), equilibrium gas adsorption analysis and dynamic breakthrough measurement associated with a high adsorption capacity of 2.65 mmol g-1 at 25 °C and 1.01 bar and 0.81 mmol g-1 at 25 °C and 0.15 bar. This rationally designed N-doped carbon aerogel with specific interfacial structures and high CO2 adsorption capacity, high selectivity, and adsorption performance remained pretty stable after multiple uses.

Nitrogen doping in porous biochar from cotton stalk with H3PO4 activation for reduction of NOx with NH3-SCR at low temperatures: Characteristics and catalytic activity analysis

This study aimed to prepare a series of nitrogen-doped modified biochar using the cotton stalk as the raw material and examine the effect of different nitrogen-containing groups on the NH3-selective catalytic reduction (SCR) reaction. The X-ray photoelectron spectroscopy results and denitration activity analysis revealed that the pyridine nitrogen (N-5) and pyrrole nitrogen (N-6) were the main nitrogen-containing groups determining the denitration activity of the biochar. The NO-temperature-programmed desorption results showed that the surface basicity of the biochar after nitrogen doping increased, and its adsorption capacity for NO improved. The results of the NO oxidation test indicated that the SCR reaction on the biochar existed as both a “fast-SCR” reaction and a “standard-SCR” reaction. That is, the NH3-SCR reaction mainly depended on the “fast-SCR” reaction at low temperatures (50–150℃). The main reaction at high temperatures (150–260℃) was the “standard-SCR” reaction. The O2-TPD results showed that the biochar doped with nitrogen produced a large number of oxygen holes, increasing the O2 activation ability of the biochar. Both E-R and L-H mechanisms existed in the denitrification process of the nitrogen-doped cotton stalk-based biochar, and both gaseous and adsorbed NO were obtained by •NH2 reduction.

Preparation of Carbon Dots with Ultrahigh Fluorescence Quantum Yield Based on PET Waste.

Environmentally friendly polyethylene terephthalate-based carbon dots (PET-CDs) with ultrahigh fluorescence quantum yield were prepared with waste PET textiles as raw materials. First, oligomers were prepared from the reaction of waste PET textile and ethylene glycol by the microwave method. Then, the mixture without isolation and purification as well as pyromellitic acid and urea were adopted as precursors for the preparation of PET-CDs by the hydrothermal method. It was found that the as-prepared PET-CDs had a spherical structure with an average particle size of 2.8 nm. The carbon core of PET-CDs was a graphene-like structure doped with nitrogen atoms in the form of pyrrole nitrogen and the surface contained −NH2, which is convenient for modification and functionalization with various materials in the form of chemical bonds. The as-prepared PET-CDs exhibit excitation-independent emission properties in the range from 340 to 440 nm, and the best excitation and emission wavelengths of PET-CDs are 406 and 485 nm, respectively, while the fluorescence quantum yield is 97.3%. In terms of the application, the as-prepared PET-CDs could be adopted as a fluorescence probe for the detection of Fe3+, and the limit of detection is as low as 0.2 μmol/L. The mechanism of PET-CDs by Fe3+ was found to be the static quenching mechanism. In addition, PET-CDs can be used in LEDs and fluorescent anticounterfeiting.

Efficient CO2 adsorption on porous carbon with nitrogen functionalities based on polybenzoxazine: High-pressure adsorption characteristics

Ordered-interconnected porous carbon with nitrogen functionalities is a potential adsorbent for CO2 capture since it could adsorb CO2 gas through both physical and chemical mechanisms. Herein, we reported the preparation of ordered-interconnected porous carbons having nitrogen functionalities based on polybenzoxazine using a silica templating method. The CO2 adsorption measurement was performed at 30 °C and the pressure was varied from 1 to 40 bar. The results showed that the specific surface area (SSA) and pore volume showed a correlation trend indicating the increase with increasing silica templates up to 40 % and the carbon samples contained nitrogen functionalities on the surface (pyrrolic and pyridonic nitrogen, pyridinic nitrogen, and oxidized nitrogen). After CO2 activation, the nitrogen functionalities are still present on the surface of the porous carbon and the sample based on 40 wt% of silica (AC40%Si-800) exhibited the greatest SSA (1,391 m2/g) with extremely large pore volume (3.77 cm3/g). This led to the largest amount of CO2 uptake (25.07 mmol/g at 40 bar) recorded to date. For the first time, the computational study revealed that only pyridinic nitrogen (N-6) is capable of chemically adsorbing CO2 molecules via Lewis acid-base interaction, which synergistically enhanced the adsorption capability.

Simultaneously speciation of mercury in water, human blood and food samples based on pyrrolic and pyridinic nitrogen doped porous graphene nanostructure

A rapid and efficient method based on a novel nitrogen-doped porous graphene nanostructure (NDPG) was used for the speciation of mercury in water and human blood samples by the CV-AAS. The mixture of the NDPG, ionic liquid, and acetone was rapidly injected into the human blood, water, and food samples for mercury separation by the cloud point assisted dispersive ionic liquid-micro solid-phase extraction (CPA-DIL-μ-SPE) at pH 7.5. The UV-microwave accessory converted the organic mercury (R-Hg) to inorganic mercury, and total mercury (TM) was determined. Finally, the organic mercury was calculated by subtracting the inorganic and entire mercury contents. By optimizing, the linear range, LOD, and enrichment factor were obtained (0.01–6.80 µg/L; 0.005–3.60 µg/L), (2.6 ng/L; 1.2 ng/L) and (9.8; 20.2) for the mercury species in human blood and water/food samples, respectively (Mean of RSD < 1.9 %). The CRM samples obtained the validation of the procedure.

Puzzling Out the Structure of Novofumigatamide: Total Synthesis of Constitutional Isomers. Part II.

The total synthesis of several constitutional isomers showing a different connectivity of the macrolactam ring with the hexahydropyrrolo[2,3-b]indole core, as well as those arising from the positional exchange of the valine and the anthranilate units of the structure originally proposed for (−)-novofumigatamide, has been carried out. The constitutional isomers with 12-membered ring macrolactam connected with the pyrroloindoline framework through the indole nitrogen, and the acetyl group at the pyrrole nitrogen, of endo relative configuration, were prepared through the condensation between the tryptophan and valine edges derived from l- or d-tryptophan and l-valine amino acids. The corresponding exo products are highly unstable structures difficult to isolate and characterize. A second group of isomeric structures synthesized considered the positional exchange between the valine and the anthranilate residues within the macrolactam ring in the originally proposed macrocyclic structure. Comparison of the spectroscopic data allowed us to discard these alternative structures for the natural product.

Mechanism study of N2 formation from dinitrogen-containing carbonaceous materials during coal pyrolysis

N2 is an important nitrogen-containing product in the process of coal pyrolysis, and understanding its formation mechanism is crucial to control NOx emissions in coal combustion. In this paper, the pyrrole-pyridine dinitrogen structure and dipyridine nitrogen structure were selected as the carbonaceous surfaces to investigate effect of different nitrogen forms on N2 production. The density functional theory (DFT) was used to study the formation mechanism of N2 in the process of pyrolysis at the microscopic level. The calculation results show that the form of nitrogen does not change the process of coal pyrolysis to N2. Both of the two dinitrogen char models experienced four processes: nitrogen stripping, nitrogen migration, the second nitrogen stripping and N2 desorption. However, the different nitrogen forms would result in different charge distribution and Mayer bond order in the structure. The presence of pyrrole nitrogen endowed N8 and C9 having relatively strong positive and negative Mulliken atomic charges, respectively, which increased the Mayer bond order between C9 and N8, resulting in a higher activation energy for the stripping of N8 atom from the pyrrole ring. As a result, the char model with dipyridine nitrogen was easier to pyrolysis to N2. The theoretical calculation results also reveal that the energy barriers needed to be overcome at the rate-determining step in the pyrolysis of pyrrole-pyridine dinitrogen structure and dipyridine nitrogen structure to N2 are 552.74 kJ/mol and 492.36 kJ/mol, which are higher than those of HCN and NH3. It well explained the experimental results that higher temperature is required for N2 generation.

Microstyling of Biofluorescence in Human Hair as Sustainable and Functional Waste

Human hair is a huge untapped waste resource whose useful compounds require toxic and environmentally harmful chemicals to extract. Herein, the optical properties of human hair without using such chemicals, turning waste into a site‐selective multicolored display, and a chemical sensor with a visual indicator through tunable fluorescence are transformed. The tunable fluorescence color, which includes both visible light and infrared components, is achieved using a scanning laser beam (microscopic) and hotplate heating at a low temperature of 360 °C for 3 min (macroscopic and large‐scale production). These fluorescing hair readily detects methylene blue molecules within a concentration range of 10−12–10−21 M due to the formation of tryptophan byproducts and electron contributing pyrrolic nitrogen. This work's simple yet impactful consequence lays the foundation on which the industrial applicability of the functionalized human hair waste can be achieved, realizing a possible cyclical economy through sustainable resources.

Removal of phenylarsonic acid compounds by porous nitrogen doped carbon: Experimental and DFT study

Phenylarsonic acids are deemed as emerging contaminants, and their removal by carbonaceous materials has aroused wide attentions. However, the adsorption behaviors and mechanisms on nitrogen doped carbon still remain unclear. Herein, nitrogen doped porous carbons (NC-x) for adsorbing p-arsanilic acid and roxarsone were fabricated by hydrothermal and following activation treatment of peanut shell. The results revealed that NC-750 which was activated at 750 °C exhibited high BET surface area of 1331.11 m2/g, total pore volume of 0.97 cm3/g and average pore size of 2.91 nm, and its maximum equilibrium capacities based on Sips model for p-arsanilic acid and roxarsone were 287.3 mg/g and 462.6 mg/g, respectively. The sufficient adsorption space, rich defect structure and high affinity of nitrogen-containing groups endow NC-750 with high adsorption capacities, and the adsorption mechanisms involve with pore-filling, hydrogen bonding and π-π interactions. Density functional theory (DFT) calculation demonstrated that p-arsanilic acid was electron donor while roxarsone was electron acceptor, and graphitic nitrogen was conducive to the π-π interactions while pyrrolic nitrogen and pyridinic nitrogen were preferential for hydrogen bonding interactions. This work can provide reference for understanding the adsorption behaviors and interfacial mechanisms between phenylarsonic acid and nitrogen doped carbonaceous materials.

An oxygen reduction reaction electrocatalyst tuned for hydrogen peroxide generation based on a pseudo-graphite doped with graphitic nitrogen

The carbon material, GUITAR (pseudo-graphite from the University of Idaho thermolyzed asphalt reaction) can be doped with nitrogen in two prevalent forms. In a previous study N(py)-GUITAR had a predominance of pyridinic and pyrrolic moieties with no graphitic nitrogen. In this study N(g)-GUITAR contains a 9.7 % N atomic abundance, with that fraction consisting of 72.3 % graphitic, 23.7 % pyridinic, and 0 % pyrrolic nitrogen. The two materials allow for the examination of hypotheses regarding the importance of the three different nitrogen moieties in the oxygen reduction reaction (ORR). In the previous investigation, the lack of graphitic nitrogen of N(py)-GUITAR gave a preferred pathway of 4e- ORR to H2O. In this investigation, N(g)-GUITAR gave a 2e- ORR pathway to H2O2. This was elucidated by current efficiency and hydrodynamic voltammetry studies. The high predominance of graphitic nitrogen confirms the hypothesis regarding 2e- vs. 4e- ORR pathways with N-doped carbon materials. N(g)-GUITAR was also evaluated for parasitic pathways for H2O2 production. At -0.95 V vs. Ag/AgCl the combination of current efficiency for H2O2 is 96 % in 0.05 M Na2SO4 with a production rate of 4.9 mg cm-2 h-1, is the highest reported in the literature. This indicates possibilities for water purification and treatment applications, which require 10 to 250 mg L-1, depending on conditions.

The Oxygen Reduction Activity of Nitrogen-doped Graphene

Abstract Graphite nitrogen, pyridine nitrogen and pyrrole nitrogen are the main nitrogen types in nitrogen-doped graphene materials. In order to investigate the mechanism of the oxygen reduction activity of nitrogen-doped graphene, several models of nitrogen-doped graphene with different nitrogen contents and different nitrogen types are developed. The nitrogen content is varied from 1.3 at% to 7.8 at%, and the adsorption energy is calculated according to the established models, then the band gaps are analyzed through the optimization results, so as to compare the magnitude of the conductivity. Finally, the oxygen reduction activity of graphite nitrogen-doped graphene (GNG) is found to be better than pyridine nitrogen-doped graphene (PDNG) and pyrrole nitrogen-doped graphene (PLNG) when the nitrogen content is lower than 2.6 at%, and the oxygen reduction activity of PDNG is the best when the nitrogen content was higher than 2.6 at%.

Carbon Nanodots with Nearly Unity Fluorescent Efficiency Realized via Localized Excitons.

Carbon nanodots (CDs) have emerged as an alternative option for traditional nanocrystals due to their excellent optical properties and low toxicity. Nevertheless, high emission efficiency is a long‐lasting pursuit for CDs. Herein, CDs with near‐unity emission efficiency are prepared via atomic condensation of doped pyrrolic nitrogen, which can highly localize the excited states thus lead to the formation of bound excitons and the symmetry break of the π–electron conjugation. The short radiative lifetimes (<8 ns) and diffusion lengths (<50 nm) of the CDs imply that excitons can be efficiently localized by radiative recombination centers for a defect‐insensitive emission of CDs. By incorporating the CDs into polystyrene, flexible light‐converting films with a high solid‐state quantum efficiency of 84% and good resistance to water, heating, and UV light are obtained. With the CD–polymer films as light conversion layers, CD‐based white light‐emitting diodes (WLEDs) with a luminous efficiency of 140 lm W−1 and a flat‐panel illumination system with lighting sizes of more than 100 cm2 are achieved, matching state‐of‐the‐art nanocrystal‐based LEDs. These results pave the way toward carbon‐based luminescent materials for solid‐state lighting technology.

Pyrrole derivatives as interlayer modifier of Li-S batteries: Modulation of electrochemical performance by molecular perturbation

The electrochemical performance of lithium-sulfur (Li-S) batteries is strongly hampered by the shuttle effect and slow redox kinetics of lithium polysulfides (LiPSs). Surface modified interlayer of a separator of Li-S batteries is demonstrated to be an effective strategy to overcome this problem. Herein, cobalt nanoparticles confined in nitrogen co-doped porous carbon framework (Co-CN) were developed from pyrolysis of ZIF-67 and used as interlayer of PP separator for Li-S batteries, and were functionalized by four pyrrole derivatives, 1-phenylpyrrole, 1-methyl pyrrole, 1-(p-toluenesulfonyl) pyrrole, and 1-pyrrole, respectively, which were screened in terms of the electron-withdrawing/donating ability of the substituent groups on the pyrrolic nitrogen. The impact of the molecular structure of pyrrole derivatives on the interaction with LiPSs and the electrochemical performance of Li-S batteries were explored by nuclear magnetic resonance and theoretical calculation. It is uncovered that 1-phenylpyrrole shows the highest enhancement of redox kinetics of LiPSs, attributing to the optimal interaction with Co nanoparticles and LiPSs. Therefore, 1-phenylpyrrole modified Co-CN interlayer enables the best electrochemical performance for the Li-S batteries, delivering a specific capacity of 562 mAh g−1 at 5 C and a capacity of 538, 526, and 449 mAh g−1 after 500 cycles at 1, 2, and 3 C, respectively. At a high sulfur loading of 5.5 mg cm−2, it achieves a capacity of 440 mAh g−1 after 500 cycles at 1 C. This work reveals the interaction mechanism among LiPSs, Co nanoparticles and the molecular modifiers in improving the electrochemical performance of Li-S batteries.

Catalytic ozonation performance of calcium-loaded catalyst (Ca-C/Al2O3) for effective treatment of high salt organic wastewater

A novel Calcium-loaded catalyst (Ca-C/Al2O3) was prepared with a facile impregnation method, using polyethyleneimine (PEI)-polydopamine (PDA) as a coating agent and Al2O3 as supporter. The prepared Ca-C/Al2O3 catalyst showed a higher treatment performance for high salt organic wastewater, and removal rate of chemical oxygen demand (COD) was enhanced from 32.5% to 64.4% comparing with single ozonation. Besides, it also showed a good catalytic performance comparing with other catalysts reported in different literature. Catechol groups and reactive amine groups in the PEI-PDA coating worked as anchoring points for metal ions, facilitating the formation of dispersed calcium sites (Ca-O and Ca-N). Calcium sites and different types of nitrogen (graphite nitrogen, pyrrolic nitrogen, and pyridinic nitrogen) were identified as the active sites for the catalytic reaction. The analysis of electron paramagnetic resonance (EPR) and radical quenching tests revealed that hydroxyl radical (•OH) and singlet oxygen (1O2) were the reactive oxygen species (ROS) for treatment of high salt organic wastewater. According to the above results, the prepared Ca-C/Al2O3 catalysts showed a good catalytic permanence and used for advanced treatment of high salt organic wastewater.

Oil origin and migration direction in Wushi sag, Beibuwan Basin, South China Sea

The Wushi sag is one of the most important petroleum-bearing units located in the Beibuwan Basin, South China Sea. Insufficient understanding of oil origin and migration direction, and lack of characterizing oil differential accumulation distribution patterns in Wushi sag greatly restrict further hydrocarbon exploration. In this study, oil-source rock genetic relationships and migration directions were analyzed in detail by combining geochemical analysis of 45 source rock samples, 23 crude oil samples, 12 oil sandstone samples, and basin modeling results. The geochemical data show there is distinguishable heterogeneity in Liushagang Formation (Fm) source rock in Wushi sag, which is divided into two types. The first type (including the Member (Mbr) 23 and Mbr 3 of Liushagang Fm source rocks) was deposited in a weak reducing to suboxic and fresh to brackish water environment with a predominance of aquatic algal plankton input. The second type (including the Mbr 1 and Mbr 21 of Liushagang Fm source rocks) was deposited in a suboxic and fresh to brackish water environment with mixed inputs of aquatic algal plankton and terrestrial higher plants. Three groups of crude oils (A, B, and C) are identified using their physical properties and biomarker data. The group A oil is characterized by a higher abundance of oleanane, lower abundance of C30 4-methylsterane, higher values of Pr/Ph, and lighter δ13C values, and is mainly derived from the Mbr 21 of Liushagang Fm source rock. Group B and group C oils are characterized by a lower abundance of oleanane and higher abundance of C30 4-methylsterane, but present some differences in Pr/Ph and δ13C values. Both groups of oils are sourced from the Mbr 23 of Liushagang Fm source rock, and their differences in geochemical characteristics indicate the lateral heterogeneity of source rock. Oil migration directions are determined by combining maturity parameters, pyrrolic nitrogen compounds, and also basin modeling results. The preferential oil migration directions in Wushi sag are from the central to the northeast and south of the sag. The accumulation distribution of different groups of oils is mainly controlled by the vertical and lateral heterogeneity of Mbr 2 of Liushagang Fm source rock.

MOF-derived Co nanoparticle on nitrogen-rich carbon for fatty acid hydrotreatment into green diesel

The green diesel from lipid hydrotreatment can replace directly the fossil diesel. In order to solve the problem of Co agglomeration, Co nanoparticle on nitrogen-rich carbon (Co-NP/NC) was synthesized by using the Co-MOF as precursor. After tuning the method of Co-MOF preparation and the subsequent pyrolysis temperature, the preparation parameters of Co-NP/NC were optimized. At 220 °C, the oleic acid hydrotreatment over Co-NP/NC-1:20-400 catalyst attained 99.6% conversion and 99.6% alkane yield, much higher than that over traditional Co/AC (76.8% conversion and 14.9% total alkane yield). The apparent activation energy of octadecanol hydrotreatment over Co-NP/NC-1:20-500 was much lower than Co/AC (148.86 vs. 204.01 kJ/mol), further revealing the high catalytic performance of Co-NP/NC catalyst. From the characterizations of Co-NP/NC series catalysts, the highly dispersed Co nanoparticles with 4.37 nm, abundant pyridine nitrogen and pyrrole nitrogen as well as the layered morphology providing sufficient active area contributed the decent activity in lipid deoxygenation.

Valorization of orange peel waste to tunable heteroatom-doped hydrochar-derived microporous carbons for selective CO2 adsorption and separation

Constrained by the extortionately expensive carbon sources, low carbon yields, inadequate adsorption capacities, and corrosive chemical activating agents, the commercialization of carbonaceous CO2 adsorbents remains a challenging task. Herein, potassium oxalate (K2C2O4), an activating agent with less corrosive properties, was used for the synthesis of activated carbons from inexhaustibly available “orange peel biowaste.” For the first time, a comprehensive report is presented on the effect of hydrothermal treatment, hydrochar/K2C2O4 ratio, activation temperature, and melamine modification in tailoring the porosity and surface functionalization of activated carbons. The optimized sample, OPMK-900, exhibited large specific surface area ~2130 m2/g; micropore volume ~1.1166 cm3/g, and a high pyrrolic nitrogen content (~ 46.1 %). Notably, melamine played the dual role as a promoter to K2C2O4 porosity generation and a nitrogen dopant, which synergistically led to an efficient CO2 uptake of ~6.67 mmol/g at 273 K/ 1 bar via micropore-filling mechanism and Lewis acid–base interactions. Moreover, remarkably high IAST CO2/N2 selectivity (105 at 273 K and 96 at 298 K) surpasses most of the biomass-derived carbons. Furthermore, the moderately high isosteric heat of adsorption (∆Hads ~ 38.9 kJ/mol) revealed the physisorption mechanism of adsorption with a limited energy requirement for the regeneration of the spent adsorbents.

S-Doping Promotes Pyridine Nitrogen Conversion and Lattice Defects of Carbon Nitride to Enhance the Performance of Zn–Air Batteries

The efficient operation of Zn-air batteries (ZABs) requires highly active and stable reversible air catalysts. Studies have shown that heteroatom-doped carbonaceous nanomaterials are effective metal-free electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Herein, we design a facile and scalable catalyst doping scheme to manufacture S-doped carbon nitride (S-C3N4). Surprisingly, this metal-free catalyst exhibits excellent OER and ORR electrocatalytic activities in alkaline electrolytes, being comparable to those of commercial Pt/C. For the first time, it is proved by experiments that S doping can not only effectively increase the lattice defects of C3N4 but also promote the conversion of pyrrolic nitrogen to pyridine nitrogen, thereby enhancing the bifunctional catalytic activity (OER and ORR). When the catalyst is used as an air electrode for rechargeable ZABs, its performance is obviously better than that provided by commercial Pt/C. Our findings and material design strategies are expected to provide new ideas for the synthesis of various high-performance carbon-based electrocatalysts.