Electron Transfer Number Research Articles

Construction of Biosensing System for Glycated Albumin Using an Electron Transfer Peptide-Modified Protein Probe.

Glycated albumin (GA) is one of the proteins that replaces several sugar moieties and can be used as an indicator of diabetes mellitus. We developed a sensing system that uses GA in the early detection of diabetes mellitus. In this study, H6Y4C acetylated (Ac-) at the N-terminals of the peptide was combined with wheat germ agglutinin (WGA) to recognize glucose moieties. The Ac-H6Y4C-WGA was constructed as a GA-sensing probe. The tyrosine residues of Y4C exhibited an oxidation peak, and His-tag moieties were introduced to separate Ac-H6Y4C-WGA in the synthesis of the probe. The Ac-H6Y4C-WGA probe binds with the 1-2 molecules of Ac-H6Y4C per WGA using matrix assisted laser desorption/ionization-time of flight (MALDI-TOF)-MS. Next, the functions of Ac-H6Y4C-WGA were evaluated using voltammetry. The number of electron-transfers was calculated based on the relationship between the peak potential and logarithm of scan rate and was 3.03. In the electrochemical measurements with mannose and bovine serum albumin, the peak currents were similar to that of GA alone. By contrast, a decrease in the peak current was suppressed when glucose was added to the solution containing the probe. As a result, Ac-H6Y4C-WGA was selectively bound to the glucose moieties of GA. The calibration curve via differential pulse voltammetry was proportional to the concentrations of GA and ranged from 1.0 × 10-12 to 2.0 × 10-11 M with a detection limit of 3.3 × 10-13 M.

Formation Mechanism of Environmentally Persistent Free Radicals on Alkaline Earth Oxide Surfaces.

The formation of environmentally persistent free radicals (EPFRs) is usually related to transition-metal oxides in particulate matter (PM). However, recent studies suggest that alkaline-earth-metal oxides (AEMOs) in PM also influence EPFRs formation, but the exact mechanism remains unclear. Here, density functional theory calculations were performed to investigate the formation mechanism of EPFRs by C6H5OH on AEMO (MgO, CaO, and BaO) surfaces and compare it with that on transition-metal oxide (ZnO and CuO) surfaces. Results indicate that EPFRs can be rapidly formed on AEMOs by dissociative adsorption of C6H5OH, accompanied by electrons transfer. As the alkalinity of AEMOs increases, both adsorption energy and the number of electron transfers gradually increase. Also, the stability of the formed EPFRs is mainly attributed to the electrostatic and van der Waals interactions between the phenoxy radical and surfaces. Notably, the formation mechanism of EPFRs on AEMOs is similar to that on ZnO but differs from that on CuO, as suggested through geometric structure and charge distribution analyses. This study not only elucidates the formation mechanisms of EPFRs on AEMOs but also provides theoretical insights into addressing EPFRs pollution.

Quantitative characterization of the contribution of electrogenerated active species for NH+ 4-N oxidation on Ti/RuO2-IrO2 anode

The contribution of active species for ammonia nitrogen (NH4+-N) oxidation has received much attention in recent decades through electrocatalytic oxidation (EO) technology. Here we describe the strong NH4+-N removal capacity (more than 98 %) with NaCl as electrolyte of Ti/RuO2-IrO2 anode. Electrochemical tests were used to characterize the excellent NH4+-N degradation performance of Ti/RuO2-IrO2 anode in presence of chlorides. The values of electron transfer number (n = 1.02) and transfer coefficient (α = 0.42) show that the reaction is in the diffusion control stage, which is more conducive to the degradation of NH4+-N. Additionally, three active species (•OH, Cl•, and ClO•) formation is related to the adsorption energy (obtained by density functional theory (DFT) calculation) during the electrolysis process. The difference charge density and density of state (DOS) calculation indicate that the O − in ClO• is more likely to break and react with pollutants in water, which is consistent with the results of active species detection experiments. The combination of kinetics (Tafel) and thermodynamics (adsorption energy) shows that the variation of Tafel slope is affected by the coverage of active species on the electrode surface.

Co‑MOF-Derived Flake-Like Co3O4 Supported Pd Nanoparticles as High-Performance Hydrogen Peroxide Electroreduction Catalysts

Development of highly efficient catalysts for the hydrogen peroxide reduction reaction (HPRR) has been a focus of research for fuel cells using hydrogen peroxide (H2O2) as an alternative cathode oxidant. The carbon-doped flake-like cobalt oxide electrode (Co3O4@C NF) was prepared on nickel foam (NF) by annealing the metal organic framework (MOF). A Co3O4@C/Pd NF (CPNF) electrode was derived from Co3O4@C NF by supporting Pd nanoparticles. Half-cell tests demonstrated that the CPNF electrode exhibited outstanding catalytic performance. The CPNF electrode displayed a high current density of 932 mA cm−2 at −0.8 V (vs Ag/AgCl). This aligns with its low activation energy (7392.8 J mol−1). The electron transfer numbers for the Co3O4@C NF and CPNF electrodes were 2.97 and 3.32, respectively. Incorporating CPNF as the cathode of Direct borohydride-hydrogen peroxide fuel cell (DBHPFC) yielded notable catalytic performance, with a peak power density of 68 mW cm−2. The CPNF electrode exhibited remarkable stability, sustaining continuous current discharge for over 20 h. These electrochemical properties result from the structural characteristics obtained through MOF annealing, which increases the number of exposed active sites and enhances ion transport. Therefore, CPNF stands as a promising cathode catalyst for DBHPFC.

The first-principles study on the magnetic and electronic properties of Janus Cr-based MXene

Using the first-principles calculations, the geometric, magnetic and electronic properties of two-dimensional Janus MXenes Cr2CAB (A/B = F, O, OH) were investigated. The results show that Cr2COF, Cr2CO(OH) and Cr2CF(OH) all exhibit A-type antiferromagnetic. The Janus MXene Cr2CO(OH) and Cr2COF are half metals with the atomic orbital of Cr-d and O-p states contributing to the metal states at the Fermi level in spin up channel. However, Cr2CF(OH) is a semiconductor. Bader charge and geometric structure analyses show that the electron transfer number difference between the O2- and F-/OH- groups and the bond length difference between Cr-O and Cr-OH/F lead to an unequal interaction at the two ends, resulting in a transition from semiconductor properties of Cr2CT2 (T = F, OH) to half metal of Cr2CAB (A = O; B = F, OH). These findings highlight the importance of surface groups on tuning the magnetic and electronic properties of MXene, which benefits to the applications of two-dimensional Janus MXenes in spintronics.

Metal-organic framework-derived two-dimensional in-plane Janus catalysts promoting oxygen electroreduction to hydrogen peroxide.

We use MOFs material as precursor to synthesize carbon based two-dimensional (2D) materials loaded with In2 S3 -In2 O3 (In-S-O) nanoparticles. The In-S-O nanoparticles have exhibited Janus architecture composed of two compounds with different crystal structures that are combined in-plane on 2D carbon material surface. The excellent properties of this in-plane Janus material include 2D nanoarchitecture and its Janus properties formed by combining two different crystal structures. It has exhibited excellent electrochemical performances due to its abundant electrochemical active sites and large specific surface area. According to experiments, the electron transfer number of the material for two-electron oxygen reduction is about 2.4, and the hydrogen peroxide yield is 32 mg/h cm2 . In the further test of liquid flow electrolytic cell, the yield can reach up to 172 mg/h cm2 .

Exploring Fibrin Protein Hydrogels for the Production of Heteroatom‐Doped Porous Carbon Nanoarchitectures as Efficient Metal‐Free Oxygen Reduction Reaction Catalysts

Although protein hydrogels are excellent carbonization precursors for synthesizing carbon nanoarchitectures as efficient metal‐free oxygen reduction reaction (ORR) catalysts, research on this topic has rarely been conducted. In this study, fibrin protein hydrogels templated with sodium chloride (NaCl) crystals are proposed as novel precursors for the manufacture of heteroatom‐doped planar carbon nanostructures containing internal pores. By systematically adjusting the carbonization conditions, it is revealed that their effects on material properties and ORR characteristics. The catalyst carbonized at 900°C for 12 hr demonstrated excellent performances in an alkaline solution, including onset potential (Eon; 0.86 V vs. reversible hydrogen electrode), diffusion‐limited current (–4.0 mA cm−2 at 0.05 V), electron transfer number (2.84), and durability (–18 mV shift in Eon after 30,000 cycles). This is attributed to the synergistic action of fast out‐of‐plane electron transport, sufficient adsorption sites, enhanced activity by heteroatom doping, and effective mass transfer through interconnected pores.

Изменение состава твердых нестехиометрических соединений методом ионного переноса

The paper presents results of measuring electron and ion transfer numbers of titanium hydride, carbide and nitride. It is shown that these compounds had mixed electron-ionic (anionic) conductivity. The dependences of the ion transfer number on the non-metal content in titanium carbide and nitride were obtained, and the change of the non-metal content under the influence of an electric field was studied. The non-metal atoms in non-stoichiometric titanium carbide and nitride were located in the octahedral voids of the titanium cubic lattice, forming a non-metal sublattice. Non-stoichiometric titanium hydride had a fluorite-type cubic crystal lattice, and the hydrogen atoms were located in the tetrahedral voids of the cubic titanium lattice. In titanium boride, ionic conductivity appeared near compounds of stoichiometric composition. It is shown that the formation of interstitial phases corresponded to the Hegg criterion. Due to the existence of vacancies in the non-metal sublattice, ion transfer was possible under the influence of an electric field, resulting in a chemical composition change of non-stoichiometric compounds. Analysis of the physicochemical properties of non-stoichiometric transition metal compounds was carried out as an opportunity to detect the ionic conductivity of carbides, nitrides and oxides.

Preparation and characterization of palladium nanoparticle-embedded carbon nanofiber membranes via electrospinning and carbonization strategy.

Carbon nanofiber membranes (CNMs) are expected to be used in many energy devices to improve the reaction rate. In this paper, CNMs embedded with palladium nanoparticles (Pd-CNMs) were prepared by electrospinning and carbonization using polyimide as the raw material. The effects of carbonization temperature, carbonization atmosphere, and heating rate on the physicochemical properties of the as-obtained Pd-CNMs were studied in detail. On this basis, the electrocatalytic performance of Pd-CNMs prepared under optimal conditions was characterized. The results showed that highly active zero-valent palladium nanoparticles with uniform particle size could be distributed on the surface of carbon nanofibers. Under vacuum conditions, at a carbonization temperature of 800 °C and a heating rate of 2 °C min-1, Pd-CNMs have lower H2O2 yield, lower Tafel slope (73.3 mV dec-1), higher electron transfer number (∼4), and superior durability, suggesting that Pd-CNMs exhibit excellent electrocatalytic activity for ORR in alkaline electrolyte. Therefore, polyimide-derived CNMs embedded with Pd nanoparticles are expected to become an excellent cathode catalyst layer for fuel cells.

Synthesis of MnOOH and its application in a supporting hexagonal Pd/C catalyst for the oxygen reduction reaction.

With the expansion of global energy problems and the deepening of research on oxygen reduction reaction (ORR) in alkaline media, the development of low cost and high electrocatalytic performance catalysts has become a research hotspot. In this study, a hexagonal Pd-C-MnOOH composite catalyst was prepared by using the triblock copolymer P123 as the reducing agent and protective agent, sucrose as the carbon source and self-made MnOOH as the carrier under hydrothermal conditions. When the Pd load is 20% and the C/MnOOH ratio is 1 : 1, the 20% Pd-C-MnOOH-1 : 1 catalyst obtained by the one-step method has the highest ORR activity and stability in the alkaline system. At 1600 rpm, the limiting diffusion current density and half-wave potential of the 20% Pd-C-MnOOH-1 : 1 electrocatalyst are -4.78 mA cm-2 and 0.84 V, respectively, which are better than those of the commercial 20%Pd/C catalyst. According to the Koutecky-Levich (K-L) equation and the linear fitting results, the electron transfer number of the 20%Pd-C-MnOOH-1 : 1 electrocatalyst for the oxygen reduction reaction is 3.8, which is similar to that of a 4-electron process. After 1000 cycles, the limiting diffusion current density of the 20%Pd-C-MnOOH-1 : 1 catalyst is -4.61 mA cm-2, which only decreases by 3.7%, indicating that the 20%Pd-C-MnOOH-1 : 1 catalyst has good stability. The reason for the improvement of the ORR performance of the Pd-C-MnOOH composite catalyst is the improvement of the conductivity of the carbon layer formed by original carbonization, the regular hexagonal highly active Pd particles and the synergistic catalytic effect between Pd and MnOOH. The method of introducing triblock copolymers in the synthesis of oxides and metal-oxide composite catalysts is expected to be extended to other electrocatalysis fields.

Preparation of honeycomb perovskite-type La1−xSmxMn0.8Co0.2O3 and its electrochemical performance

A series of perovskite oxides La1-xSmxMn0.8Co0.2O3 (x = 0.2, 0.4, 0.6, 0.8) were prepared using the carbon microsphere template method, and the prepared samples have a loose porous structure with a large specific surface area. Among them, the sample La0.8Sm0.2Mn0.8Co0.2O3 with doping amount x = 0.2 has higher half-wave potential, onset potential and limiting current density, which has the highest electron transfer number during the oxygen reduction reaction and is more favorable for the 4 e- reaction to occur. In addition, it has the lowest overpotential and the smallest ΔE. It has excellent bifunctional catalytic activity and shows good application prospects.

Advancing alkaline fuel-cells cathode through synergistic catalyst design: Integrated LDH-derived ternary mixed metal oxide with N/Co multi-doped reduced graphene oxide

The fabrication of efficient and affordable nanomaterials is the bottleneck in the advancement of energy conversion/storage technologies. This study presents the synthesis and performance assessment of a novel hybrid nanostructure comprising LDH-calcinated Ternary Mixed Metal Oxide (3MMO) nanoflakes, incorporated on multi-doped (Nitrogen and single atom cobalt) Reduced Graphene Oxide (CoNG), as a ptoficient electrocatalyst for Oxygen Reduction Reaction (ORR) in an alkaline environment. The synthesized nanocomposites underwent a comprehensive analysis and discussion, employing several physicochemical and electrochemical characterization methods. The physiochemical analyses collectively affirmed the successful incorporation of the 3MMO onto the CoNG lattice forming a mesoporous structure. In terms of electrochemical characterization, the 3MMO-CoNG nanocomposite displayed the most favorable electrochemical attributes, including an onset potential of −0.04 V vs. Ag/AgCl, an electron transfer number of 3.8, remarkable current retention (85 %) after an extended period of 18000 s, and the lowest charge transfer resistance (29 Ω) among the synthesized samples. The synergistic interaction between the 3MMO nanoparticles and the CoNG lattice contributes to the improved electrochemical performance of 3MMO-CoNG. The results of this investigation demonstrate that the developed catalyst displays exceptional electrochemical performance, rivaling the most effective catalysts documented in existing literature.

Metal−Organic Framework CPO-27 Derivatives As Non-Precious Metal Catalyst for Anion Exchange Membrane Fuel Cell

Fuel cell stands as an environmentally friendly technology harnessing the power of hydrogen to generate clean water. In the range of fuel cell types, the anion exchange membrane fuel cell (AEMFC) stands out, effectively converting chemical energy to electricity without relying on platinum catalyst. Nonetheless, platinum catalyst is still used in addressing the sluggishness of the oxygen reduction reaction (ORR) during AEMFC operation. The scarcity and expense of platinum, however, hinder its widespread adoption. Furthermore, in the alkaline environment, platinum surface is covered with OH species, impeding active sites and diminishing electrochemical activity. Consequently, seeking an efficient, stable, and abundant platinum substitute is a primary target in the development of fuel cell.This study focuses on the development of the non-precious metal catalyst for the ORR in AEMFC. The catalyst, denoted as NiCo2-CPO-27/PCN, is derived from a carbon nanorod structure obtained from the metal-organic framework (CPO-27). Through the optimized process, the catalyst demonstrates the distinct carbon nanorod configuration. Additionally, the NiCo2-CPO-27/PCN catalyst exhibits enhanced ORR activity, achieving the electron transfer number of 3.99, which closely approaches the ideal four-electron transfer number. This improvement in activity is attributed to factors such as the specific structure, heteroatom contribution, and coordination arrangement of the catalyst.

Tungstosilicic Acid: A Promising Electrolyte for Redox Flow Battery

Large-scale energy-storage systems are vital for the integration of renewable energy technologies. Vanadium redox flow battery (VRFB) is one of the most developed and mature energy storage technologies available today. However, VRFB suffers from low energy density and non-availability of active materials. [1]. Recently, polyoxometalates are emerging as promising electrolyte materials with high energy density owing to their capability of multi-electron-transfer per molecule and faster redox reactions [2-3]. From the number of polyoxometalates which are available, tungstosilicic acid (TSA) is a good candidate as a negative electrolyte and is investigated in RFB. The equilibrium redox potential and the corresponding electron-transfer number of all the three redox peaks of TSA are determined. One electron-transfer in the first two redox peaks (0.008 V vs. RHE and –0.248 V vs. RHE) and approximately 14 electrons in the third redox reaction (-0.374 V vs. RHE) are determined using chronoamperometry. The equilibrium redox potential of the third redox peak is comparable to that of the V2+/3+ redox couple (−0.295 V vs. RHE), which is commonly used as a negative electrolyte in VRFB. There is a significant potential difference between the third redox peak of TSA (−0.374 V vs. RHE) and VO2 +/ VO2+ redox couple (1.118 V vs. RHE). The current loss due to parasitic hydrogen evolution at the third redox peak potential is very less in comparison to TSA reduction current and the same is confirmed by chronoamperometry and linear sweep voltammetry. Thus, multi-electron-transfer, optimum redox potential and negligible HER current is the motivation to fabricate a TSA-VO2+ RFB with vanadyl sulfate (VOSO4) as positive electrolyte. The high-electron transfer per TSA molecule leads to higher power density at relatively low concentrations of TSA. Power density of 100 mM TSA – 1 M VO2+ flow battery is higher than that of 1 M all vanadium RFB and the impact of concentration ratio between the electrolytes on the power density is studied. Higher concentration of vanadium electrolyte for a given TSA concentration gives better power density and charge capacity of the flow battery. On over-charging of the battery, TSA changes to irreversible state and further may precipitate [4]; thus, charging potential of RFB is optimized. The improvement in performance is also validated by the two-electrode cell electrochemical impedance spectroscopy results. Figure: Cyclic Voltammograms of 100 mM TSA in 0.5 M H2SO4 (black) over bare glassy carbon electrode, equimolar (1 M each) VO2 +/VO2+ (blue) and equimolar V3+/V2+ (red) in 3M H2SO4 over Vulcan-C coated GC electrode recorded at scan rate of 20 mV s-1.

Influence of phase structure of MnO2 for enhancing the electrochemical sensitivity of environmental pollutant chlortetracycline

Electrochemical sensing of chlortetracycline (CTC) using α and β- MnO2 nanowires has been studied. The influence of different phase structures (α and β) of MnO2 nanowires on the determination of chlortetracycline (CTC) was studied systematically. To enhance the sensitivity of MnO2, a high conductivity microporous carbon (MC) was employed as a support matrix for MnO2. The electrochemical sensing results illustrate that the α-MnO2 exhibited better electrochemical performance than β-MnO2. This better activity was correlated with its excellent properties like more exposed MnO6 edges, higher conductivity, and lowest average oxidation state . The kinetics study illustrated that the MnO2 modified electrodes perform much better than the bare electrodes. The number of electron transfer, electron transfer coefficient, and diffusion coefficient of CTC were calculated from the scan rate effect; the values are 1, 0.50, and 1.581 × 10−6 cm2 s−1 respectively. Amperometry was used to calculate the lowest detection limit (LOD) at a potential of 0.82 V. The α-MnO2/MC electrode exhibits a better linear range (1–55 µM) with a LOD value of 103 nM towards CTC. Furthermore, the proposed sensor exhibited better anti-interference ability towards KCl, kanamycin sulfate, zinc acetate, magnesium chloride, tetracycline, streptomycin sulfate, and oxytetracycline. The sensor's ability to accurately determine the level of CTC in samples of drinking water, tap water, poultry farm soil, and milk highlights its suitability for industrial applications. The developed sensor showed better reproducibility (RSD=0.45%) and repeatability (RSD=2.06%) towards CTC. Therefore, the proposed sensor can be used as a more practical platform for monitoring environmental contaminants.

Defect Engineered Ni Doped MnCO2O4 Spinel Acts as Effective Bifunctional Electrocatalyst for Rechargeable Zinc‐Air Batteries

AbstractHerein, an effective strategy using defect engineering promoted by Ni atom doping on MnCo2O4 is proposed for bifunctional catalytic activities of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A series of NixMn1‐xCo2O4 with x=0, 0.1, 0.2, and 0.3 is hydrothermally synthesized. Tuning the electronic structure by Ni‐doped MnCo2O4 results in modulating the valence states by dominating Mn4+ / Co3+ with the increase of oxygen vacancies. At optimized Ni content, Ni0.2Mn0.8Co2O4 reveals activity toward ORR with a current density of −1.02 mA cm‐2 at 0.95 V (vs. RHE), a high electron transfer number of 3.536, and the highest half‐wave potential of 0.855 V, which is comparable to Pt/C. For OER, Ni0.2Mn0.8Co2O4 demonstrates the lowest overpotential of 503 mV to achieve a current density of 10 mA cm−2. Additionally, rechargeable zinc‐air batteries (RZABs) with Ni0.2Mn0.8Co2O4 catalyst demonstrate a capacity of 808.6 mA h g−1 at 1.0 mA cm−2 with power densities of 459 mW cm−2 at 675 mA cm−2. The improved binding strength (Mn−O/Co−O bond) and the enhanced stability by Ni atom doping in MnCo2O4 for ORR/OER is proved by ex‐situ FT‐EXAFS. This work highlights defect engineering on Ni‐doped MnCo2O4 used as bifunctional ORR/OER catalysts for high‐performance RZABs.

Well-organized metal-free chemically reduced graphene oxide sheets as electrocatalysts for enhanced oxygen reduction reactions in alkaline media

Metal-free reduced graphene oxides have recently received attention as potential replacements for platinum-based electrocatalysts. In the present study, we investigated the electrochemical characteristics of chemically reduced graphene oxides (C-rGO) in oxygen reduction reactions (ORR). The C-rGO displays significantly enhanced catalytic activity towards the ORR in alkaline solutions compared to the starting graphene oxide (GO). The thermal properties of C-rGO show good thermal stability, and structural defects in C-rGO were confirmed by Raman analysis. Electrochemical impedance spectroscopy (ESI) analysis confirmed C-rGO superior electron transport capacity over GO. The onset potential (0.82 V), lower Tafel slope, and current density (-5.6 × 10-4 mA/cm2) of the C-rGO catalysts were increased compared to GO due to the majority of functional groups removed after chemical reductions. It's clear that catalysts work through four electron (e-) ORR processes bacause the C-rGO has higher electron transfer numbers (3.8 at a potential of −0.63 V).

Monodispersed Co-N3 loaded carbon nitride mediated peroxymonosulfate activation for rapid degradation of trace urea via singlet oxygen

The removal of trace urea presents a significant challenge in the production of electronic-grade ultra-pure water (UPW). This study proposed a simple strategy to regulate the low-coordination of a single-atom cobalt catalyst (RyCo-CN0.20) for the efficient removal of trace urea via peroxymonosulfate (PMS) activation. The optimal R0.50Co-CN0.20 with low-coordination Co-N3 sites was constructed by in-situ reduction of NaBH4 and significantly enhanced the PMS activation. The removal efficiency of trace urea achieved 94 % within 5 mins. The kobs of trace urea degradation in R0.50Co-CN0.20/PMS system reached 0.4576 min−1, which was much higher than previous reported systems. Experiments of free radical quenching and electron paramagnetic resonance demonstrated that singlet oxygen species were the dominant free radical. The corresponding steady concentration of singlet oxygen species in the R0.50Co-CN0.20/PMS system was enhanced to be 16.361 × 10–6 μM, which was twice of Co-CN0.20/PMS. Density functional theory calculations revealed that the optimized electron distribution of the Co center in the Co-N3 sites processed a higher d band center (−1.08 eV) and richer electron transfer number (0.75 e−) compared with Co-N4 sites, hence realizing the stronger PMS activation. Continuous operation verified that R0.50Co-CN0.20/PMS could maintain the removal rate of trace urea above 80 % after 150 h operation. Moreover, R0.50Co-CN0.20/PMS in the pilot UPW production process effectively reduced the pollution caused by trace urea and ensured the quality of the terminal UPW (Total organic carbon <1 μg/L). This study provides a new approach for the removal of trace urea through PMS activation by low-coordination single-atom catalysts.

Preparation of Fe, N co-doped oxygen reduction catalysts from sacrificial templates and their application to Zn-air batteries

Fe, N co-doped non-precious metal oxygen reduction catalysts has been prepared with nitrogen-rich precursor material (g-C3N4) as a self-sacrificing template and N source. The utilization of g-C3N4 as a nitrogen-rich material could anchor the Fe source sufficiently on its surface, and form abundant active sites. The g-C3N4-derived carbon has a high specific surface area, which facilitates the more active sites to be exposed, and the suitable pore structure provides a site for the oxygen reduction reaction. The half-wave potential of the catalyst is optimized to 0.85 V by doping with different Fe-content sources, exceeding that of commercial 20% Pt/C catalysts. The prepared catalysts also exhibit excellent electron transfer numbers along with superior methanol resistance. The prepared catalysts is loaded into Zn-Air battery devices and presenting high open-circuit voltage, power density, and specific capacitance performance. This work provides an economical and feasible preparation strategy to explore nitrogen-rich precursor materials as Fe-N-C type efficient oxygen reduction catalysts.

Fast and Sensitive Detection of CO by Bi-MOF-Derived Porous In2O3/Fe2O3 Core-Shell Nanotubes.

In2O3 is an optimal material for sensitive detection of carbon monoxide (CO) gas due to its low resistivity and high catalytic activity. Yet, the gas response dynamics between the CO gas molecules and the surface of In2O3 is limited by its solid structure, resulting in a weak gas response value and sluggish electron transport. Herein, we report a strategy to synthesize porous In2O3/Fe2O3 core-shell nanotubes derived from In/Fe bimetallic organic frameworks. The fabricated porous In2O3/Fe2O3-4 core-shell nanotubes present outstanding gas sensitivities, including a response value 3.8 times (33.7 to 200 ppm CO at 260 °C) higher than that of monometallic-derived In2O3 (8.7), ultrashort response and recovery times (23/76 s) to 200 ppm CO, low detection limit (1 ppm), promising selectivity, and long-term stability. The enhanced sensing mechanisms are clarified by the combination of experiment and first-principles calculations, showing that the synergetic strategy of higher adsorption energy, increased electrical conductivity, higher electron transfer numbers, and larger specific surface area of porous core-shell structures promotes the surface activity and charge transfer efficiency. The present work paves a way to tune gas-sensing materials with special morphologies for the development of high-performance CO sensors.