High Catalytic Activity Research Articles

Atomically Dispersed Iridium on Polyimide Support for Acidic Oxygen Evolution.

Designing a high-performing iridium (Ir) single-atom catalyst is desired for acidic water electrolysis, which shows enormous potential given its high catalytic activity toward acidic oxygen evolution reaction (OER) with minimum usage of precious Ir metal. However, it still remains a substantial challenge to stabilize the Ir single atoms during the OER operation without sacrificing the activity. Here, we report a high-performing OER catalyst by immobilizing Ir single atoms on a polyimide support, which exhibits a high mass activity on a carbon paper electrode while simultaneously achieving outstanding stability with negligible decay for 360 h. The resulting electrode (denoted as Ir1-PI@CP) reaches a 49.7-fold improvement in mass activity compared to the counterpart electrode prepared without polyimide support. Both our experimental and theoretical results suggest that, owing to the strong metal-support interactions, the polyimide support can enhance the Ir 5d states of Ir single atoms in Ir1-PI@CP, which can tailor the adsorption energies of intermediates and decrease the thermodynamic barrier at the rate-determining step of the OER, but also facilitate the proton-electron-transfer process and improve the reaction kinetics. This work offers an alternative avenue for developing single-atom catalysts with superior activity and durability toward various catalytic systems and beyond.

Novel Insight into the Synergistic Mechanism for Pd and Rh Promoting the Hydro-Defluorination of 4-Fluorophenol over Bimetallic Rh-Pd/C Catalysts.

This study explores the synergistic effect between the Rh and Pd of bimetallic Rh-Pd/C catalysts for the catalytic hydro-defluorination (HDF) of 4-fluorophenol (4-FP). It was found that 4-FP could not be efficiently hydro-defluorinated over 6% Pd/C and 6% Rh/C due to the inherent properties of Pd and Rh species in the dissociation of H2 and the activation of C-F bonds. Compared with 6% Pd/C and 6% Rh/C, bimetallic Rh-Pd/C catalysts, especially 1% Rh-5% Pd/C, exhibited much higher catalytic activity in the HDF of 4-FP, suggesting that the synergistic effect between the Rh and Pd of the catalyst was much more positive. Catalyst characterizations (BET, XRD, TEM, and XPS) were introduced to clarify the mechanism for the synergistic effect between the Rh and Pd of the catalyst in the HDF reaction and revealed that it was mainly attributed to the bifunctional mechanism: Pd species were favorable for the dissociation of H2, and Rh species were beneficial to the activation of C-F bonds in the HDF reaction. Meanwhile, the interaction between Rh and Pd species enabled Rh and Pd to exhibit a more positive synergistic effect, which promoted the migration of atomic H* from Pd to Rh species and thus enhanced the HDF of 4-FP. Furthermore, 1% Rh-5% Pd/C prepared using 20-40 equiv NaBH4 exhibited the best performance in the catalytic HDF of 4-FP. Catalysis characterizations suggested that appropriate Rh3+/Rh0 and Pd2+/Pd0 ratios were beneficial to the dissociation of H2 and the activation of C-F bonds, which caused the more positive synergistic effect between the Rh and Pd of Rh-Pd/C in the HDF reaction. This work offers a valuable strategy for enhancing the performance of catalytic HDF catalysts via promoting synergistic effects.

Sensitive electrochemical determination of quercetin and folic acid with cobalt nanoparticle functionalized multi-walled carbon nanotube.

A nanocomposite of cobalt nanoparticle (CoNP) functionalized carbon nanotube (Co@CNT) was prepared and used to modifyaglassy carbon electrode (Co@CNT/GCE). Characterization indicates the morphology of Co@CNT is CoNPs adhering on CNTs.With the nano-interface, Co@CNT provideslarge surface area, high catalytic activity, and efficient electron transfer, which makes Co@CNT/GCE exhibiting satisfactory electrochemical response toward quercetin (QC) and folic acid (FA).The optimumpH values for the detection of FA and QC are 7.0 and 3.0, respectively. The saturated absorption capacity (Γ*) and catalytic rate constant (kcat) of Co@CNT/GCE for QC and FA are calculated as 1.76 × 10-9, 3.94 × 10-10mol∙cm-2 and 3.04 × 102, 0.569 × 102M-1∙s-1. The linear range for both FA and QC is estimated to be 5.0nM-10μM, and the LODs (3σ/s) were 2.30nM and 2.50nM, respectively. The contents of FA and QC in real samples determined by Co@CNT/GCE are comparable withthe results determined by HPLC. The recoveries were in the range 90.5 ~ 114% and the total RSD was lower than 8.67%, which further confirms the reliability of the proposed electrode for practical use.

Synthesis and characterization of azo cross‐linked polymer as a new catalyst for the production of hydrogen gas by methanolysis of NaBH4

AbstractThe intensive use of fossil fuels has profound impacts on all ecosystems, primarily contributing to global warming through greenhouse gas emissions. To mitigate these impacts, alternative energy sources like hydrogen are crucial. In this study, azo cross‐linked polymer with 4‐aminophenyl sulfone and resorcinol were synthesized by a green synthesis method. The polymer was extensively characterized by Fourier‐transform infrared spectroscopy, Brunner‐Emmett‐Teller analysis, thermogravimetric analysis, and scanning electron microscopy‐energy dispersive x‐ray spectroscopy analyses. Subsequently, the catalytic performance of the polymer in hydrogen production from NaBH4 via methanolysis was investigated. At this stage, the parameters affecting hydrogen production (catalyst and NaBH4 amounts, MeOH volume and temperature) were systematically studied to determine optimum conditions. The maximum HGR values of the polymer was 13,100 and 27,000 mL min−1 gcat−1 at 30 and 60°C, respectively and its activation energy was 10.45 kJ mol−1. After optimization, the reusability of azo polymer was tested with 5 cycles. The theoretical volume of hydrogen was produced in all 5 cycles. But with each cycle, the hydrogen production time increased. The main purpose of this study was to demonstrate novel azo‐linked polymers with high catalytic activity in hydrogen production. The results revealed significant potential of the polymer for hydrogen generation. Overall, this research highlights the promising role of azo cross‐linked polymers as effective catalysts for hydrogen production, offering new perspectives and pathways towards sustainable energy solutions.

Enhanced CO2 Methanation over Nickel‐Based Unsupported Catalyst Synthesized by Chemical Precipitation Method

AbstractThis study investigated the catalytic CO2 methanation using nickel oxide (NiO) nanoparticles and nickel oxalate (NiC2O4) as catalysts. The NiC2O4 precursor was synthesized through a chemical precipitation reaction between nickel (II) nitrate hexahydrate (Ni(NO3)2.6H2O) and oxalic acid (H2C2O4.2H2O). Nickel oxide (NiO) nanoparticles were synthesized through thermal decomposition of NiC2O4 precursor at 450 °C in air. The samples were characterized by XRD, FTIR, BET, SEM, and EDX. The XRD and FTIR analyses revealed that the NiO nanoparticles were well‐crystallized having size 17.30 nm. The BET analysis of the NiO sample revealed mesoporous NiO nanoparticles with a specific surface area (SBET) of 29.08 m2/g and a narrow distribution of pore sizes. The catalytic performance of NiO and NiC2O4 catalysts studied for the CO2 methanation in tubular packed bed reactor at 150–550 °C and 1 atm. The reduced NiO nanoparticles exhibited more catalytic activity than the decomposed NiC2O4 catalyst. At 380 °C, 1 atm, and gas hourly space velocity (GHSV) of 9000 mL g−1 h−1, the reduced NiO nanoparticle catalyst showed high catalytic activity, with a maximum CO2 conversion of 85.54 %, 99 % CH4 selectivity, and 84.69 % CH4 yield. Furthermore, the NiO nanoparticle catalyst demonstrated excellent stability after 12 h of streaming at 380 °C.

Diiron Complexes with Rigid and Conjugated S-to-S Bridges for Electrocatalytic Reduction of CO2.

Electroreduction of CO2 to value-added low-carbon chemicals is a promising way for carbon neutrality and CO2 utilization. It was found that the diiron complex [(μ-bdt)Fe2(CO)6] (bdt = benzene-1,2-dithiolate) has high catalytic activity for electrocatalytic CO2 reduction. To further study the effect of the S-to-S bridge on the catalytic performances of diiron complexes for electrochemical CO2 reduction, four diiron complexes 1-4 with different rigid and conjugated S-to-S bridges were either selected or designed. The electrocatalytic studies showed that under optimal conditions, 2 with a 2,3-naphthalenedithiolato bridge exhibited the lowest catalytic onset potential (Eonset = -1.75 V vs Fc+/0), while 4 with a diphenyl-1,2-vinylidene bridge displayed the highest catalytic activity (TOFmax = 295 s-1), which is 1.5 times that of [(μ-bdt)Fe2(CO)6]. The controlled potential electrolysis experiments of 4 in 0.1 M MeOH/MeCN at -2.35 V vs Fc+/0 gave a total faradaic yield close to 100%, with selectivities of 77%, 9%, and 14% for HCOOH, CO, and H2, respectively. The mechanism for CO2 reduction was studied using density functional theory, IR spectroelectrochemistry, and electrochemical methods. The results indicate that modifying the structure of the S-to-S bridge is an effective strategy to improve the catalytic performance of diiron complexes for electrocatalytic CO2 reduction.

Chitosan Nanocomposites-Based Electrochemical Sensors: A Review

Chitosan nanocomposites represent a promising class of materials formed by combining chitosan with various nanomaterials. This innovative approach leverages the advantageous properties of both chitosan—a biopolymer known for its biocompatibility, natural abundance, high film-formability, and tunable functionality—and nanomaterials, which exhibit enhanced properties such as high surface area, electrical conductivity, and catalytic activity. While chitosan alone is limited by its low electrical conductivity and mechanical strength, its integration with nanomaterials addresses these shortcomings, enhancing its utility in electrochemical sensing applications. This review comprehensively summarizes recent advancements in chitosan-based nanocomposites, mainly focusing on their application in electrochemical sensors. It discusses the various nanocomposites combined with metals, metal oxides, carbon-based materials, and other nanostructures. The review highlights the synthesis methods, performance metrics, and potential applications of these sensors across fields such as environmental monitoring, food safety, medical diagnostics, and pharmaceuticals. Emphasis is placed on the advancements over the past five years, with a discussion on the significant impact these sensors have had in detecting critical analytes like heavy metals, neurotransmitters, glucose, and reactive oxygen species.

Effect of Li-Na sorbent phase in Ru/Al2O3 dual function materials for the Integrated CO2 capture and methanation

The design of highly performing dual functional materials (DFMs) is the key to the successful deployment of Integrated Carbon Capture and Methanation (ICCM) process that combines both steps into a single unit operation with high energy efficiency. Intending to enhance the CO2 working capacity while preserving high catalytic methanation activity, herein we set out to investigate the effect of combining Li and Na as the CO2 sorbent phase in Ru/Al2O3 DFMs. ICCM tests in a fixed bed reactor operated with alternate feeds indicated that combining Na with Li (or partially substituting it for Li) effectively increases the CO2 capture capacity and methane production of the DFM. However, this generally requires higher temperatures to properly activate the catalytic methanation and to regenerate the DFM compared to a pure Li-based formulation. Transient operando DRIFTS and catalytic kinetic experiments provided mechanistic insights into the activation/inhibition of different reaction paths on those DFMs containing only Li and/or Na.

Eco-friendly and large-scale fabrication of NiMoN/Ni(OH)2/NF as highly efficient and stable alkaline hydrogen evolution reaction electrode

Bimetallic nickel-molybdenum nitride (NiMoN) catalysts have attracted great attention due to their remarkable similarity to group VIII noble metals in terms of electronic structure, good electron conductivity, and durability for the hydrogen evolution reaction (HER). However, the existing approaches for fabricating NiMoN catalysts usually entail a series of multiple steps and hazardous ammoniated ingredient. As a result, these methods are difficult to be scaled up for large-area fabrication towards industrial water splitting. Herein, a hierarchical composite NiMoN@Ni(OH)2@NF composite electrode with a sheet morphology was synthesized based on a rational combination of seawater etching and magnetron sputtering. This method is easily scalable for producing large-area electrodes with minimal pollution. The incorporation of Ni(OH)2@NF nanoarray carriers enhances the exposure of additional active sites on the NiMoN layer, thereby augmenting the electrochemically active specific surface area of the electrode.The as-synthesized NiMoN@Ni(OH)2@NF electrode demonstrates excellent HER activity, with an overpotential of 57 mV at 10 mA cm−2, and exhibits remarkable long-term catalytic stability for over 100 h at a current density of 100 mA cm−2.This study presents an eco-friendly and straightforward method for preparing large-scale transition metal nitride catalysts with high catalytic activity.

Amphiphilic Janus Particles for Aerobic Alcohol Oxidation in Oil Foams.

Amphiphilic Janus silica particles, tunable with oleophobic-oleophilic properties and low fluorine content (8 wt % F), exhibited prominent foamability for a variety of aromatic alcohols at low particle concentrations (<1 wt %) compared to randomly functionalized silica particles. When selectively loaded with Pd nanoparticles on the oleophilic hemisphere, the particles displayed more than a 2-fold increase in catalytic activity for the aerobic oxidation of benzyl alcohol compared to nonfoam bulk catalysis under ambient O2 pressure. The particles were conveniently recycled with high foamability and catalytic activity maintained for at least five consecutive runs.

Ppb-level H2 Gas-sensor based on Porous Ni-MOF derived NiO@CuO Nanoflowers for Superior Sensing Performance

Nickel oxide (NiO) is an optimal material for precise detection of hydrogen (H2) gas due to its high catalytic activity and low resistivity. However, the solid structure of NiO imposes limitations on the gas response kinetics of H2 gas molecules, resulting in a slower electron-hole transit and reduced gas response value. Herein, a unique NiO@CuO NFs with porous sharp-tip and nanospheres morphology was successfully synthesized by using a metal-organic framework (MOF) as a precursor. The fabricated porous 2 wt% NiO@CuO NFs describes outstanding selectivity towards H2 gas, including a high sensitivity of response value (170 to 20 ppm at 150°C), is almost 28.3% higher than that of porous Ni-MOF, low detection limit (300 ppb) with a notable response (21), short response and recovery times at (300 ppb, 40/63 s and 20 ppm, 100/167 s), exceptional long-term stability and repeatability. The study also explored the impact of relative humidity to evaluate the sensor performance under real-world conditions. The boosted hydrogen dioxide sensing properties may be attributed to synergistic effects of numerous factors including p-p heterojunction at the interface between NiO and CuO nanoflowers, especially a porous sharp-tip MOF structure and rough surface of nanospheres as well as the chemical sensitization effect of NiO. This research offers a viable method for creating unique MOS heterostructures from Ni-MOF and CuO that have unique morphologies and compositions that could be used for H2 gas sensing applications.

The application of a novel biomimetic enzyme p-BEs cascade catalytic platform for the rapid detection of glucose

The blood glucose concentration in aquatic organisms, a crucial indicator reflecting their health status, holds significant importance for detecting glucose levels in serum in terms of processing and quality monitoring. In this study, a novel POD biomimetic enzyme (p-BEs) with horseradish peroxidase catalytic properties was designed, optimized, and its mechanism was discussed in detail. Based on this, a portable system has been developed capable of determining glucose levels in three ways: quantitatively analyzed through UV–Vis/MD, quantitatively analyzed on-site using a mobile phone RGB, and semi-quantitatively analyzed through a drip plate. Meanwhile, compared with other catalytic methods for detecting glucose, we achieved a lower limit of detection (0.03 μM) and shorter detection time (12 min), with high catalytic activity. This study provides new insights into the design of efficient and reliable cascade catalytic systems responsive to glucose, offering a low-cost, simplicity of operation method for glucose detection.

The methane dry reforming reaction was conducted using a combination of lamellar vermiculite molecular sieve and highly active perovskite catalyst

Dry reforming of methane (DRM) enables the conversion of two greenhouse gases, CH4 and CO2, into syngas, offering remarkable environmental and economic benefits. The primary challenge in this process lies in maintaining the catalyst's high catalytic activity and stability. In this study, natural vermiculite (VMT) was employed to modify the layer carrier with a large specific surface area and suitable pore size. By combining the structural characteristics of perovskite, we synthesized the LaNiO3/VMT-SiO2 perovskite catalyst using the citric acid complex method for methane dry reforming reaction. The results demonstrate that at T = 750 °C and GHSV = 36,000 mL/(h·gcat), the catalyst exhibits excellent activity (achieving maximum conversions of 82% for CO2 and 90% for CH4) as well as stability (up to 24 h). Characterization techniques such as XRD and TEM revealed that the catalyst possesses exceptional catalytic activity and stability due to its horizontally distributed active component Ni within perovskite. Through pretreatment, we obtained an active component Ni with small particle size and uniform dispersion along with a carrier featuring a large specific surface area. Furthermore, alkaline La2O3 in the reduced catalyst enhances its carbon resistance.

Hydrogenation of inert aromatic compounds under mild conditions catalyzed by confined trimetal sites in porous metal silicate materials

Complete hydrogenation of aromatic compounds is an important subject in various industry fields. However, due to the high stabilization energy of aromatic compounds resulting from their high aromaticity and non-polarity, the hydrogenation reaction is usually performed under harsh reaction conditions in the presence of noble metal-based catalysts. We report herein a porous metal silicate (PMS) material PMS-58, which consists of Cu, Ce and Co trimetal active sites, demonstrating high catalytic activity and selectivity in hydrogenating of a series of aromatic compounds under mild conditions (60oC and 0.5MPa H2). PMS-58 is superior to the previously reported non-noble metal-based catalysts and could be favorably compared to noble metal-based catalysts. The unique catalytic properties of PMS-58 are derived from the synergistic work of trimetal sites with Ce species serving as strong Lewis acid sites for dissociation of dihydrogen, Co species stabilizing Cu(I) species, and Cu(I) species playing a crucial role in activating aromatic rings. Therefore, this work provides a new approach in developing highly efficient non-noble metal catalysts for complete hydrogenation of arenes under mild conditions, which could be applied in removal of aromatic compounds in petroleum products.

Front Cover: Insights into the High Catalytic Activity of Li‐Ion Battery Waste toward Oxygen Reduction to Hydrogen Peroxide (ChemElectroChem 15/2024)

Front Cover: Insights into the High Catalytic Activity of Li‐Ion Battery Waste toward Oxygen Reduction to Hydrogen Peroxide (ChemElectroChem 15/2024)

Flexible Scaffold Modulation of Spatial Structure and Function of Hierarchically Porous Nanoparticle@ZIF-8 Composites to Enhance Field Deployable Disease Diagnostics.

Catalytic nanoparticle@metal-organic framework (MOF) composites have attracted significant interest in point-of-care testing (POCT) owing to their prominent catalytic activity. However, the trade-off between high loading efficiency and high catalytic activity remains challenging because high concentrations of nanoparticles tend to cause the misjoining and collapse of the MOFs. Herein, a facile strategy is reported to encapsulate high concentrations of platinum (Pt) nanoparticles into zeolitic imidazolate framework-8 (ZIF-8) using polydopamine (PDA) as a support for Pt@ZIF-8 and as a flexible scaffold for further immobilization of Pt nanoparticles. The resulting composite (Pt@ZIF-8@PDA@Pt) exhibits ultrahigh Pt nanoparticle loading efficiency, exceptional catalytic activity, stability, and a bright colorimetric signal. Following integration with lateral flow immunoassay (LFIA), the detection limits for pre- and post-catalysis detection of B-type natriuretic peptide (NT-proBNP) are 0.18 and 0.015ng mL-1, respectively, representing a 6-fold and 70-fold improvement compared to gold nanoparticle-based LFIA. Moreover, Pt@ZIF-8@PDA@Pt-based LFIA achieves 100% diagnostic sensitivity for NT-proBNP in a cohort of 184 clinical samples.

High-temperature stable chromium complexes bearing fluorinated PNP ligands for selective ethylene tetramerization toward 1-octene

A series of new fluorinated PNP ligands of bis(ortho-fluorophenyl)-type (L1-L2) and ortho-fluorophenyl-type (L3-L4) have been synthesized and assessed for the selectivity of ethylene oligomerization. Compared to the non-fluorinated analogue ligand L6, the fluorinated ligand L1 exhibited approximately three times high catalytic activity. The bis(ortho-fluorophenyl)-type ligand L2 with a diethylphosphine substituent offered the highest catalytic performance of 3548 kg∙g−1∙h−1 and the 1-octene selectivity is 67.6 %. Both the L1 and L2 ligands exhibited excellent the activity of catalyst at a high temperature of 100 ℃, with ligand L2 providing the catalytic performance of 1587 kg∙g−1∙h−1 and good selectivity of 47.5 % for 1-C8=. The ortho-fluorophenyl substituent enhances the catalytic activity, while the para-fluorophenyl substituent reduces the catalytic activity. In addition, density functional theory (DFT) calculations and UV–vis spectroscopy have been used to rationalize the role of the fluorine effect in promoting catalytic performance. Our results indicated that the strong inductive effect of fluorine atoms and the non-covalent interaction between fluorine atoms and active centers jointly enhance the stability of the ortho-fluorophenyl-based catalyst and promote its overall activity.

Ultrasensitive detection of mycotoxins using a novel single-Atom, CRISPR/Cas12a-Based nanozymatic colorimetric biosensor

Aflatoxin B1 (AFB1) is a typical mycotoxin in cereals, posing a significant threat to the ecology and public health. Overall, the development of nanozymatic sensors with good specificity, high sensitivity, and a clear catalytic mechanism seems to be a challenge for CRISPR/Cas detection of non-nucleic acid targets. In this study, a series of Fe-N-C single-atom enzymes (SAzymes) and Fe-Co magnetic nanoparticles (MNPs) were synthesized via pyrolysis. Fe-N-C SAzymes with high peroxidase-mimetic activity were successfully utilized as TMB chromogenic catalysts for detecting AFB1 via the CRISPR/Cas12a colorimetric aptamer sensor. In the absence of the AFB1 target, its aptamer bound to crRNA and activated the trans-cleavage activity of Cas12a, indiscriminately cutting single-stranded DNA and releasing significant amounts of Fe-N-C SAzymes into the supernatant, which catalyzed the change of TMB to blue. The synthesized Fe-Co MNPs not only effectively reduced the background signal but also significantly reduced the assay cost. This study combined SAzymes with CRISPR/Cas12a technology for the first time for non-nucleic acid target detection. The combination of Fe-N-C SAzymes’ high catalytic activity and stability, and the CRISPR/Cas12a system’s high specificity and signal amplification, significantly improved the detection system’s sensitivity and specificity, enabling the detection of other targets by substituting the aptamers. Additionally, the potential active sites and catalytic mechanism of Fe-N-C SAzymes were investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) simulations. This scheme provides a general method for constructing high-density Fe-N-C SAzymes and offers both experimental and theoretical guidance for understanding their catalytic mechanism.

P-doped MoS2 nanosheets embedded in 3D porous carbon for electrocatalytic hydrogen evolution reaction

Due to its inherent electrochemical catalytic activity, molybdenum sulfide (MoS2) is a potential electrocatalyst for hydrogen evolution reaction (HER). However, the limited exposure of its active sites resulting from the easy stacking of nanosheets and inert basal plane hampered its optimal catalytic activity. Herein, we developed a novel facile hydrothermal method to prepare phosphorus-doped MoS2 nanosheets anchored on agar-derived 3D nitrogen-doped porous carbon (P-MoS2/NC). The synthesized P-MoS2/NC electrocatalyst possesses high HER catalytic activity with a low overpotential of 167 mV at 10 mA cm−2 and a small Tafel slope of 45 mV dec−1. The excellent performance is attributed to the unique 3D network carbon structure, which avoids the stacking of the MoS2 sheets resulting in more exposed active sites. Additionally, the P atom introduced on the surface of MoS2 sheets successfully activated the in-plane inertness. This work provides an efficient strategy for designing and preparing high-quality catalysts with enhanced electrocatalytic HER activity.

Stability of Nitrogen-Doped Activated Carbon as an Electrocatalyst for the Oxygen Reduction Reaction in Various Storage Media

Besides outstanding catalytic performance, the stability of nitrogen-doped carbon materials during storage is equally crucial for practical applications. Therefore, we conducted the first investigation into the stability of highly nitrogen-doped activated carbon (AC-NC-T) obtained by modifying activated carbon with CO2/NH3 in different storage media (air, vacuum and N2). The results of the catalysis of the oxygen reduction reaction and the activation of peroxymonosulfate for degrading bisphenol A by AC-NC-T show that the catalytic activity of AC-NC-T stored in air decays most prominently, while the performance attenuated only marginally when stored in vacuum and N2. The results from N2 adsorption isotherms, Raman spectroscopy, elemental and X-ray photoelectron spectroscopy indicate that the decline in catalytic activity is due to the presence of oxygen in the environment, causing a decrease in absolute contents of pyridinic N (N-6) and graphitic nitrogen (N-Q). After being stored in an air atmosphere for 28 days, the absolute contents of N-6 and N-Q in AC-NC-950 decreased by 19.3% and 12.1%, respectively. However, when stored in a vacuum or N2, the reduction in both was less than 7%. This study demonstrates that reducing oxygen concentration during storage is crucial for preserving high catalytic activity of nitrogen-containing carbon materials.