High-efficiency Catalysts Research Articles

Flower-like NiCo2O4 spinel microspheres for efficient chlorine evolution under neutral conditions

Dimensional stability anodes (DSA), constructed using noble metal oxides like RuO2 and IrO2, is widely used in industrial chlorine production. The DSA electrode demonstrates exceptional chlorine evolution capabilities in acidic solutions and high-chloride concentrations. However, under neutral conditions, its chlorine evolution efficiency diminishes significantly. In this paper, a low-cost, high-efficiency 3D flower-like NiCo2O4 catalyst was fabricated that exhibits high catalytic activity in neutral sodium chloride solutions. The 3D flower-like NiCo2O4 catalyst exhibits good chlorine evolution efficiency, achieving 90 % at 30 mA/cm2 in NaCl solutions. Furthermore, it's chlorine evolution efficiency of the electrocatalyst surpasses that of commercial DSA electrode at various current densities, making it a highly promising candidate for electrocatalytic applications.

Unravelling the role of work function difference on supported Ru nanoclusters for alkaline hydrogen evolution reaction

Fine tuning the work function difference (ΔΦ) between support and Ru which in turn affects the electron distribution of Ru is an effective method for the design of high-performance alkaline hydrogen evolution reaction (HER) catalysts. However, it remains a challenge to understand the intrinsic relationship between HER activity and ΔΦ at the atomic level. Herein, taking N doped graphene supported Ru nanoclusters (Ru/CxNy) as the theoretical model, we demonstrate that the HER activity can be correlated with the variation of ΔΦ. For Ru/C50 with smaller ΔΦ, we find that the Ru atoms located at the top layer of Ru nanoclusters (Ru-t) with lower coordination numbers are the main reaction sites. For Ru/C30N20 with larger ΔΦ, the stronger charge redistributions of Ru is observed, and the electron-deficient Ru atoms closing to the interface (Ru-i) are the main reaction sites with significant improvement HER activity. Our findings demonstrate the role of ΔΦ on Ru/CxNy systems for the alkaline HER, which can provide valuable theoretical guidance for the design of high efficient HER catalysts.

Synthesis and HER properties of honeycomb Mo2WS6/NF nanorod array solid solution alloys

The electrolytic water-based hydrogen production demonstrates exceptional selectivity, minimal environmental impact, and superior purity of the generated hydrogen, thereby presenting promising prospects for a wide range of applications. The scarcity and high cost of Pt-based catalysts for industrial applications necessitate the development of low-cost, stable, and efficient transition metal electrocatalysts for hydrogen electrochemical precipitation (HER). In this paper, Mo2WS6 nanorod array with honeycomb structure was successfully synthesized via one-step hydrothermal vulcanisation of transition metals W and Mo on nickel foam (NF) substrate. The honeycomb nanorod array structure exhibits enhanced specific surface area and abundant active sites, and the well-defined pore structure facilitates the transport of electrolyte and reactive substances. The intrinsic activity of the active sites is significantly enhanced by the synergistic effect of MoS2 and WS2, facilitated by the formation of solid solution alloys. Excellent HER performance (η10=63 mV, η100=183 mV) was demonstrated in alkaline electrolyte (1.0 M KOH) with a corresponding Tafel slope of 93 mV dec−1. Furthermore, Mo2WS6 exhibited excellent stability after undergoing 5000 cycles of charge/discharge and a constant voltage test lasting for 96 hours. This study provides a novel approach for facile synthesis of high-efficiency HER catalysts by a one-step hydrothermal method.

Synergistic Effects of Amine Functional Groups and Enriched-Atomic-Iron Sites in Carbon Dots for Industrial-Current-Density CO2 Electroreduction.

Metal phthalocyanine molecules with Me-N4 centers have shown promise in electrocatalytic CO2 reduction (eCO2R) for CO generation. However, iron phthalocyanine (FePc) is an exception, exhibiting negligible eCO2R activity due to a higher CO2 to *COOH conversion barrier and stronger *CO binding energy. Here, amine functional groups onto atomic-Fe-rich carbon dots (Af-Fe-CDs) are introduced via a one-step solvothermal molecule fusion approach. Af-Fe-CDs feature well-defined Fe-N4 active sites and an impressive Fe loading (up to 8.5wt%). The synergistic effect between Fe-N4 active centers and electron-donating amine functional groups in Af-Fe-CDs yielded outstanding CO2-to-CO conversion performance. At industrial-relevant current densities exceeding 400mA cm-2 in a flow cell, Af-Fe-CDs achieved >92% selectivity, surpassing state-of-the-art CO2-to-CO electrocatalysts. The in situ electrochemical FTIR characterization combined with theoretical calculations elucidated that Fe-N4 integration with amine functional groups in Af-Fe-CDs significantly reduced energy barriers for *COOH intermediate formation and *CO desorption, enhancing eCO2R efficiency. The proposed synergistic effect offers a promising avenue for high-efficiency catalysts with elevated atomic-metal loadings.

Efficient catalytic combustion of propane at low temperature based on ignition effect caused by amorphous atomic-layer Pt clusters

Developing highly active catalysts for hydrocarbon combustion at low temperatures is paramount but yet challenging. The crystal form of carrier and the dispersion degree of active species have great influence on propane combustion catalysts, but its internal mechanism is still unclear. In this study, the amorphous atomic-layer Pt clusters (AL) and Pt single atoms (SA) on TiO2 with various crystal phases were prepared and used as propane combustion catalysts, where the as-synthesized Pt/a-TiO2 catalyst with atomic-layer Pt clusters exhibited better catalytic performance. The Pt/a-TiO2-AL could achieve a 90 % propane conversion (T90) at 230 °C, with the highest reaction rate (39.57 × 10−7 mol g−1 s−1) and TOF value (7.72 × 10−2 s−1) at 240 °C. Kinetic studies showed that oxygen had a lower inhibitory effect on Pt/a-TiO2-AL compared to that on the Pt/p-TiO2-AL and Pt/r-TiO2-AL catalysts; simultaneously, the Pt/a-TiO2-AL catalyst presented lower apparent activation energy compared with Pt/a-TiO2-SA. DFT results showed that atomic-layer Pt clusters on TiO2 had the lower formation energy of oxygen vacancy than Pt single atoms due to the synergistic effect between adjacent exposed Pt atoms in the fully exposed atomic-layer Pt clusters, which had a higher activation capacity for oxygen and thus accelerated propane combustion through the ignition effect (rapid activation of oxygen and rapid combustion of propane). Our primary results provide a promising approach for the creation of high-efficiency Pt-based catalysts, specifically tailored for the catalytic combustion of volatile organic compounds (VOCs).

Separation and reutilization of heavy metal ions in wastewater assisted by p-BN adsorbent

Extracting heavy metal ions from wastewater has significant implications for both environmental remediation and resource preservation. However, the conventional adsorbents still suffer from incomplete ion removal and low utilization efficiency of the recovered metals. Herein, we present an extraction and reutilization method assisted by porous boron nitride (p-BN) containing high-density N atoms for metal recovery with simultaneous catalyst formation. The p-BN exhibits stable and efficient metal adsorption performance, particularly for ultra-trace-level water purification. The distribution coefficients towards Pb2+, Cd2+, Co2+ and Fe3+ can exceed 106 mL g−1 and the residual concentrations that reduced from 1 mg L−1 to 0.8–1.3 μg L−1 are much lower than the acceptable limits in drinking water standards of World Health Organization. Meanwhile, the used p-BN after Co ion adsorption can be directly adopted as a high-efficiency catalyst for activating peroxymonosulfate (PMS) in organic pollutant degradation without additional post-treatment, avoiding the secondary metal pollution and the problems of neglected manpower and energy consumption. Moreover, a flow-through multistage utilization system assisted by p-BN/polyvinylidene fluoride (PVDF) membrane is constructed for achieving both metal ion separation and reutilization in the removal of organic pollutants, providing a new avenue for sustainable wastewater remediation.

Invigorating active sites for amorphous/crystalline heterophased co-based oxyhydroxide/tungstate toward enhanced electrocatalytic oxygen evolution: Trimetallic codoping-achieved synergistic regulation

Designing high-efficiency multimetal-based catalysts for oxygen evolution reaction at low overpotential is a grand challenge in alkaline water splitting due to the elusive synergistic effect between metal atoms. Blind pursuit of polymetallic miscibility cannot linearly enhance catalytic activity; instead, it incurs increased costs. Herein, we reported a facile trimetallic (Cu, Fe and La) codoping approach to tailor the electronic structure of Co-based oxyhydroxide/tungstate for boosting OER reaction. It was found that a better synergistic effect with Co can be exhibited only when Cu, Fe and La were coexisted in the catalyst. By virtue of this, the catalyst developed numerous oxygen vacancies, enhancing favorability for OER reaction and demonstrating high intrinsic activity. Systematic experiments additionally verified its improved reaction kinetics and optimized adsorption to intermediates. Ultimately, the prepared CoCuFeLa significantly reduced overpotential, decreasing by a minimum of 50 mV compared to monometallic doping. The alkaline electrolyzer based on the CoCuFeLa anode exhibited a low cell voltage of 1.53 V for water splitting. Remarkably, it experienced a substantial attenuation of 3.54 % after 150 h of continuous operation, attributing to the changes in the surface structure of the catalyst. This work provides a viable pathway for improving catalytic activity through multimetallic codoping, further promoting the design of more valuable multimetallic catalysts for hydrogen market.

Co8NiS8/Ni3S2 heterostructure anchored on 3D carbon nanofiber networks as a high-efficiency polysulfide catalyst for lithium-sulfur batteries

The polar Co8NiS8/Ni3S2 heterostructures anchored on 3D carbon nanofiber networks (CNFs) were prepared as catalysts modifying the separator of lithium-sulfur batteries. The Co8NiS8/Ni3S2combining the synergistic chemisorption and catalysis effect, can effectively alleviate the shuttle effect, while the CNFs further accelerate the transfer of ions and electrons through the separator. Based on the synergistic effect, the modified Li-S battery delivers a high initial specific capacity of 1532.6 mA h g−1 at 0.1C and a high reversible discharge capacity of 519.7 mA h g−1 at 2C over 500 cycles with 0.061 % decay per cycle.

Engineering of single atomic Fe-N4 sites on hollow carbon cages to achieve highly reversible MoS2 anodes for Li-ion batteries

Although the single atom electrocatalysts have been demonstrated as efficient catalysts for promoting Li2S/Na2S formation and decomposition in Li-S/Na-S batteries, the functional morphological and structural engineering capable of exposing more active sites is regarded as an essential factor to further enhance the catalytic activity. Here, we have synthesized a single atomically dispersed Fe sites embedded within hollow nitrogen doped carbon cages (Fe-N-HCN) using Fe3O4 spheres as an oxidant and sacrificial template, which is used as a high-efficiency catalyst for boosting the reversible capacity of MoS2 anode in lithium-ion batteries (LIBs). As expected, the electrochemical reaction of MoS2/Fe-N-HCN anode exhibits higher reversibility than pure MoS2 electrodes. Moreover, density functional theory is also employed to reveal that Fe-N-HCN can be effectively adsorbed and catalyze the rapid decomposition of Li2S. The hollow carbon cage structure can facilitate the exposure of the active Fe-N4 sites and favor the mass transfer during the electrochemical reactions, thus the synergistic effect of the Fe-N4 site and the hollow carbon cage structure together improve the catalytic activity for the conversion reaction of MoS2 anode.

Construction of unique oxygen vacancy defect through various metal-doping (Cu, Mn, Zr) of Ce2Co1Ox nanoparticles towards boosting the catalytic oxidation toluene performance

Achievement of catalytic oxidation of volatile organic compounds (VOCs) at low temperature is still a challenge to be addressed. Promoting catalytic activity via constructing oxygen vacancy defect is an attractive strategy in heterogeneous catalysis. Herein, a series of Ce2Co1M1 (M = Cu, Mn, Zr) catalysts were prepared by modified co-precipitation method and their catalytic oxidation performance of toluene was measured. Activity results suggested that the introduction of doping-metals significantly enhanced the catalytic performance of Ce2Co1Ox, with Ce2Co1Cu1 possessed the optimal catalytic activity (T90 = 210 ℃), robust stability, water resistance, GHSV tolerance and anti-aging ability. It has been demonstrated that Cu-doping resulted in the formation of Cu-Ce solid solution and constructed a Cu2+-O-Ce4+ complex active site. Benefiting from this, the redox and gaseous oxygen molecule capture & activation capabilities of the catalyst are tremendously improved via constructing abundant oxygen vacancies. The in-situ DRIFTS results revealed that Ce2Co1Cu1 exhibited a better C=C breaking of aromatic rings ability, a faster consumption rate of benzoate and maleic anhydride, and is less prone to accumulation of by-products, the above account for its enhanced low-temperature catalytic performance for toluene. This work may provide a new strategy to design the high-efficiency toluene oxidation catalysts.

Optimization and regulation of catalytic activity and stability: Pt–Ni diamond-shaped pearl nanochains with core-shell structure as high-efficient oxygen reduction reaction catalysts

The low utilization efficiency and poor stability of carbon-supported Pt nanoparticles (Pt/C) catalyst are two main problems of proton exchange membrane fuel cells (PEMFC), which can improve the catalytic performance by forming alloys and precisely regulating morphology and structures. Here, we introduced a simple and direct method for synthesizing Pt–Ni diamond-shaped pearl nanochains (Pt–Ni DP-NCs) as efficient electrocatalyst for oxygen reduction reaction (ORR). The alloying with Ni could enhance the catalytic activity, but because of leaching out of Ni during the cathodic reaction process, which causes a poor stability. To achieve the optimal point for both high activity and robust stability, a portion of Ni is selectively etched from Pt–Ni DP-NCs precursor in advance. During the process of de-alloying, Pt atoms with high catalytic activity are exposed to the surface of the nanochain after atomic rearrangement, thus obtaining Pt–Ni etched diamond-shaped pearl nanochains (Pt–Ni EDP-NCs) with 1D core-shell structure, which consisted of Pt–Ni as the core and Pt as the shell. Benefitting from the unique 1D core-shell structure and composition, Pt–Ni EDP-NCs-9 (etched for 9 h) exhibits high catalytic activity and robust stability for ORR. The mass activity of the sample Pt–Ni EDP-NCs-9 is 0.43 A/mgPt, which is 1.65 times higher than that of the Pt–Ni DP-NCs (0.26 A/mgPt), and 2.05 times higher than that of commercial Pt/C (0.21 A/mgPt). In addition, the 1D core-shell structure enables Pt–Ni EDP-NCs to be highly stable, which only lost by 8.6% of mass activity after 10,000 long cycles, whereas Pt–Ni DP-NCs suffers from a 34% loss under the same conditions. This work provides a strategic approach for designing efficient Pt-based catalysts that simultaneously modulate activity and stability.

Hydrogen storage properties of MgH2 modified by efficient Co3V2O8 catalyst

Developing medium temperature hydrogen storage materials is important for the practical application of the Studies have demonstrated that V-based catalysts exhibit exceptional catalytic activity in the dehydrogenation of MgH2 at medium levels. However, the V-base catalysts primarily concentrates on hydrogen desorption, and there is a necessity for further enhancement of hydrogen absorption properties. To solve this problem, herein we prepared a bimetallic oxide. Co can enhance the hydrogen absorption and desorption properties of MgH2 as the catalyst and it influences the performance of hydrogen absorption more obviously than the hydrogen desorption performance. It is found that MgH2 catalyzed by Co3V2O8 can absorb 1.31 wt% hydrogen within 30 min even under room temperature and can release 3.41 wt% hydrogen within 120 min at temperatures as low as 225 °C. The activation energy of MgH2-6 wt.%Co3V2O8 is determined to 68.5 kJ/mol, which is 50.2 % lower than that of Ball-MgH2. XRD combined with TEM measurements revealed that the in-situ formed Co and V2O3 can weaken the HH and MgH bonds respectively to improve the hydrogen storage properties of MgH2. These discoveries provide guideline of the further design of high efficiency catalysts for Mg-based hydrogen storage materials.

Ultrafine CoRu alloy nanoclusters densely anchored on Nitrogen-Doped graphene nanotubes for a highly efficient hydrogen evolution reaction

Designing highly efficient and stable electrocatalysts for hydrogen evolution reactions (HER) is essential to the production of green and renewable hydrogen. Metal-organic framework (MOF) precursor strategies are promising for the design of excellent electrocatalysts because of their porous architectures and adjustable compositions. In this study, a hydrogen-bonded organic framework (HOF) nanowire was developed as a precursor and template for the controllable and scalable synthesis of CoRu-MOF nanotubes. After calcination in Ar, the CoRu-MOF nanotubes were converted into N-doped graphene (NG) nanotubes with ultrafine CoRu nanoclusters (hereon called Co-xRu@NG-T; x = 0, 5, 10, 15, 25 representing the Ru content of 0–0.25 mmol; T = 400 °C to 700 °C) that were densely encapsulated and isolated on the shell. Taking advantage of the synergistic effects of the porous, one-dimensional hollow structure and ultrafine CoRu nanoclusters, the optimized Co-15Ru@NG-500 catalyst demonstrated superior catalytic performance for HERs in alkaline electrolytes with an overpotential of only 30 mV at 10 mA cm−2 and robust durability for 2000 cycles, which outperforms many typical catalytic materials, such as commercial Pt/C. This work introduces a novel high-efficiency and cost-effective HER catalyst for application in commercial water-splitting electrolysis.

Calcium-, magnesium-, and yttrium-doped lithium nickel phosphate nanomaterials as high-performance catalysts for electrochemical water oxidation reaction

Abstract Electrochemical water oxidation reaction (WOR) lies among the most forthcoming approaches toward eco-conscious manufacturing of green hydrogen owing to its environmental favors and high energy density values. Its vast commoditization is restricted by high-efficiency and inexpensive catalysts that are extensively under constant research. Herein, calcium, magnesium, and yttrium doped lithium nickel phosphate olivines (LiNi1−x M x PO, LNMP; x = 0.1–0.9; M = Ca2+, Mg2+, and Y3+) were synthesized via non-aqueous sol-gel method and explored for catalytic WOR. Lithium nickel phosphates (LNP) and compositions were characterized via Fourier transform infrared, scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray diffraction techniques for the structural and morphological analyses. Glassy carbon electrode altered with the LNMPs when studied in a standard redox system of 5 mM KMnO4, displayed that yttrium doped LNP, i.e. LNYP-3 exhibits the highest active surface area (0.0050 cm2) displaying the lowest average crystallite size (D avg) i.e. ∼7 nm. Electrocatalytic behavior monitored in KOH showed that LNMP-2 offers the highest rate constant “k o,” value, i.e. 3.9 10−2 cm s−1 and the largest diffusion coefficient “D o,” i.e. 5.2 × 10−5 cm2 s−1. Kinetic and thermodynamic parameters demonstrated the facilitated electron transfer and electrocatalytic properties of proposed nanomaterials. Water oxidation peak current density values were indicative of the robust catalysis and facilitated water oxidation process besides lowering the Faradic onset potential signifying the transformation of less LNP into more conducive LNMP toward water oxidation.

Synergistic Modulating Interlayer Space and Electron-Transfer of Covalent Organic Frameworks for Oxygen Reduction Reaction.

Covalent organic frameworks (COFs) are an ideal template to construct high-efficiency catalysts for oxygen reduction reaction (ORR) due to their predictable properties. However, the closely parallel-stacking manner and lacking intramolecular electron transfer ability of COFs limit atomic utilization efficiency and intrinsic activity. Herein, COFs are constructed with large interlayer distances and enhanced electronic transfer ability by side-chain functionalization. Long chains with electron-donating features not only enlarge interlayer distance, but also narrow the bandgap. The resulting DPPS-COF displays higher electrochemical surface areas to provide more exposed active sites, despite <1/10 surface areas. DPPS-COF exhibits excellent electrocatalytic ORR activity with half-wave potential of 0.85V, which is 30 and 60mV positive than those of Pt/C and DPP-COF, and is the record among the reported COFs. DPPS-COF is employed as cathode electrocatalyst for zinc-air battery with a maximum power density of 185.2mW cm-2, which is superior to Pt/C. Theoretical calculation further reveals that longer electronic-donating chains not only facilitate the formation of intermediate OOH* from O2, but also promote intermediates desorption , and thus leading to higher activity.

Ca-doped birnessite for enhanced photocatalysis of water oxidation

Birnessite is an affordable and high-efficiency catalyst for water oxidation. In this study, we attempted to doping Ca into birnessite to investigate the influence on its photocatalytic oxidation activity. The study was carried out through a combination of experimental investigations and DFT calculations of the relevant crystal and electronic structures. The analysis of Raman spectra using 2T2D correlation and DFT indicates that Ca contributes more to the high frequency regions (400–600 cm−1) than K. DFT further reveals that the introduction of Ca leads to an increase in the number of localized electrons at the Fermi energy level and in the conduction band. Photo-electrochemical experiments demonstrate a significant reduction of 100 mV/dec in the Tafel slope, along with a 1.48-fold increase in photo-current density for Ca-birnessite when compared to K-birnessite. In general, the results demonstrate that Ca-birnessite can effectively heighten visible light absorption, reduce the band gap, and enhance water oxidation activity.

Deep dive into the underlying cause of the carbon loss and the associated chemical processes in fatty acid hydrodeoxygenation over Ni@Hβ catalyst

Identification of the underlying cause of carbon loss in fatty acid hydrodeoxygenation (HDO) on the acidic catalyst is very important to understand the reaction mechanism and design high efficiency catalyst for biomass conversion. Herein, HDO reactions of palmitic acid catalyzed by Ni supported on mesoporous Beta (HBeta-M) zeolites with different acidities were investigated. It was found that a significant carbon loss (47.5%) occurred during the entire reaction process on Ni/HBeta-M catalyst with high acid density. This is because the hexadecyl ether intermediate was formed and trapped in the porous structure of the catalyst and interacted with strong acidic sites. On the Ni/HBeta-M-0.5 catalyst with medium acid density, carbon loss occurred in the initial reaction stage because hexadecanol was trapped in the porous catalyst. Investigations further demonstrated that the hexadecyl ether intermediate can also be converted to hexadecanol and hexadecane via hydrogenolysis on Brønsted acid and Ni sites.

Effective Reduction of CO2 with Aromatic Amines into N-Formamides Triggered by Noble-Free Metal-Organic Framework Catalysts Under Mild Conditions.

The reductive transformation of carbon dioxide (CO2) into high-valued N‑formamides matches well with the atom economy and the sustainable development intention. Nevertheless, developing a noble-free metal catalyst under mild reaction conditions is desirable and challenging. Herein, a caged metal-organic framework (MOFs) [H2N(CH3)2]2{[Ni3(µ3-O)(XN)(BDC)3]·6DMF}n (1) (XN = 6″-(pyridin-4-yl)-4,2″:4″,4″'-terpyridine), H2BDC = terephthalic acid) is harvested, presenting high thermal and chemical stabilities. Catalytic investigation reveals that 1 as a renewable noble-free MOFs catalyst can catalyze the CO2 reduction conversion with aromatic amines tolerated by broad functional groups at least ten times, resulting in various formamides in excellent yields and selectivity under the mildest reaction system (room temperature and 1bar CO2). Density functional theory (DFT) theoretical studies disclose the applicable reaction path, in which the CO2 hydrosilylation process is initiated by the [Ni3] cluster interaction with CO2 via η2-C, O coordination mode. This work may open up an avenue to seek high-efficiency noble-free catalysts in CO2 chemical reduction into high value-added chemicals.

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.

Tuning the Pyridine Units in Vinylene-Linked Covalent Organic Frameworks Boosting 2e- Oxygen Reduction Reaction.

The N-doped carbon materials are supposed to be the efficient oxygen reduction reaction (ORR) catalysts with the undefined N-doped carbon ring groups. It is essential to well define the role of the nitrogen atoms of these carbon structures in active behavior. Even though, the covalent organic frameworks (COFs) with precise structures are well developed, but unable to exclude the polar linkages influence. This study presents a series of pyridine-containing COFs linked via nonpolar carbon-carbon double bonds (C = C). Their catalytic activity and selectivity for 2e- ORR are successfully modulated by locating the embedded pyridine nitrogen in the backbones through the linking modes of pyridine moieties within the frameworks. Such phenomena can be attributed to their different binding abilities toward O2, leading to the different binding strength of the intermediate OH* to the catalytic sites, also verified by the theoretical calculation. This work provides us a new insight to design high-efficiency ORR catalysts through the exact location of pyridine nitrogen.