Coordination Sites Research Articles

Precise Synthesis of Dual‐Single‐Atom Electrocatalysts through Pre‐Coordination‐Directed in Situ Confinement for CO2 Reduction

AbstractDual‐single‐atom catalysts (DSACs) are the next paradigm shift in single‐atom catalysts because of the enhanced performance brought about by the synergistic effects between adjacent bimetallic pairs. However, there are few methods for synthesizing DSACs with precise bimetallic structures. Herein, a pre‐coordination strategy is proposed to precisely synthesize a library of DSACs. This strategy ensures the selective and effective coordination of two metals via phthalocyanines with specific coordination sites, such as −F− and −OH−. Subsequently, in situ confinement inhibits the migration of metal pairs during high‐temperature pyrolysis, and obtains the DSACs with precisely constructed metal pairs. Despite changing synthetic parameters, including transition metal centers, metal pairs, and spatial geometry, the products exhibit similar atomic metal pairs dispersion properties, demonstrating the universality of the strategy. The pre‐coordination strategy synthesized DSACs shows significant CO2 reduction reaction performance in both flow‐cell and practical rechargeable Zn‐CO2 batteries. This work not only provides new insights into the precise synthesis of DSACs, but also offers guidelines for the accelerated discovery of efficient catalysts.

Six element high-entropy Prussian blue analogue cathode enabling high cycle stability for sodium-ion batteries

Prussian blue analogues (PBA) are promising cathode materials for sodium-ion batteries. However, the cycle life of PBA is limited due to its structure instability during cycling. Here, we successfully introduce six transition metals into N coordination site to increase the configurational entropy, significantly improving the structure stability and cycle life of PBA cathode materials. Electrochemical characterization methods are used to compare the behavior of hexa-, penta-, quadr-, and tri-metal PBA, exhibiting the characteristic of performance increasing with entropy. Time-resolved in situ X-ray diffraction confirms the “quasi-zero-strain” structure of H-PBA during desodiation/sodiation process. X-ray absorption spectroscopy and density functional theory calculations reveal that Mn, Fe, Co and Cu contribute the high capacity of H-PBA, while Ni and Zn stabilize the structure. The strategy will inspire new ideas in designing long life cathode materials with high capacity for sodium-ion batteries.

Hexagonal boron nitride fibers as ideal catalytic support to experimentally measure the distinct activity of Pt nanoparticles in CO2 hydrogenation

Catalytic studies aim to design new catalysts to eliminate unwanted by-products and obtain 100 % selectivity for the preferred target product without losing activity. For this purpose, understanding the role of each component building up the catalyst is essential. However, determining the intrinsic catalytic activity of pure metals, especially precious metals in the CO2 hydrogenation reaction under ambient conditions is complex. This is because the catalyst supports used thus far always influence the catalytic process either directly or indirectly due to interface formation that modifies the electronic and morphological structure of the metals. Even SiO2, regarded as inert shows some activity owing to the hydroxyl groups on its surface. In this work, we propose chemically inert and defect-free hexagonal boron-nitride fibers (BNF) synthesized via a co-precipitation method with wide band gap and robust covalent bonds as an uncommon reference catalyst support to evaluate the catalytic activity of size-controlled Pt nanoparticles (4.7 ± 0.6 nm) in the hydrogenation of CO2. The fibers alone show no catalytic activity; however, Pt/BNF exhibited low but notable activity of 377 nmol/g at 400 °C and the catalyst can achieve nearly 100 % CO selectivity. X-ray photoelectron spectroscopy, transmission electron microscopy, and diffuse reflectance infrared Fourier transform spectroscopy measurements were used to indicate that hexagonal boron-nitride affects neither the metal nanoparticles nor the reaction itself; the measured catalytic activity stems from the activity of Pt deposites without the effect of the support, as they were alone. CO vibration spectroscopy studies suggest that due to the lack of substrate-metal interaction, Pt nanoparticles adopt an ideal spherical structure, resulting in several low coordination sites capable of CO2 conversion. Thus, BNF is proposed in the present article to be used as a reference catalyst support material. It can be efficiently used in investigations involving the proposed metal and reaction or under varying conditions with different metal nanoparticles and reaction systems.

Melting-dissolving kinetics and mechanism of high silica-alumina coal ash particles deposited to liquid slag wall in entrained flow gasification

The depositing and subsequent physicochemical behaviors of coal ash particles to the liquid slag wall in an entrained flow gasifier are essential to the wall reaction, slag flow and discharge. In this study, the melting-dissolving behavior and kinetics of high silica-alumina ash on the typical molten slag surface were investigated at a particle scale through in-situ melting experiments. The multifactorial effect on the ash fusibility was further evaluated. Experimental results revealed that the presence of molten slag significantly reduced the melting temperatures of high silica-alumina ash particles, with an initial melting temperature of around 1270 ℃. Dissolvability was linearly correlated with temperature, and the melting rate increased with increasing temperature or decreasing particle size. However, complete melting was difficult to achieve at 1400 ℃. Consequently, the effect of adding flux (CaO) in the molten slag on the ash fusibility was further evaluated. The ash particles achieved complete melting at a 4 wt% CaO addition, and the flux addition increased the melting rate and solubility. Besides, the mechanism-level explanation of the melting-dissolving process showed that Ca ion migration led to the transformation of aluminum to higher coordination sites, which destabilized the silica-aluminium tetrahedra structure and manifested in the generation of Bytownite macroscopically. Comparative analysis showed the melting rate depended on the diffusion process, and the melting-dissolution kinetics was established to predict the dissolution rate, which could provide a reference for the slag discharge of coals with high ash fusion temperatures in the industry.

A study on complexation of Zn(II) salts with 4-aryl-2-(pyridin-2-yl)quinolines: The influence of anions on the complex structures and their luminescent properties

A novel ligand, 6‑methoxy-4-(4-methoxyphenyl)-2-(pyridin-2-yl)quinoline (PQ) was synthesized and studied for its interaction with ZnX2.nH2O (X: Cl-, OAc-,NO3−) to form three complexes of the type [Zn(X2)(PQ)(H2O)n] (Zn1-Zn3) with high yields, ranging from 75 to 94 %. The structures of Zn1–Zn3 were fully characterized using ESI mass spectrometry, IR and 1H NMR spectroscopy, and single-crystal X-ray diffraction (for Zn1 and Zn3). Spectroscopic analyses revealed that Spectroscopic analyses revealed that the central atom Zn(II) in Zn1, Zn2, and Zn3 has the coordination numbers of 4, 5, and 6, respectively. In these complexes, Zn(II) coordinates with the PQ ligand through its two nitrogen atoms, while the remaining coordination sites are occupied by anions such as Cl-, OAc, NO3−, or by H₂O. The results also indicate that the optical properties of the Zn(II) complexes depend not only on the primary organic ligand QP but also on the secondary inorganic ligands. In THF, the complexes Zn1 and Zn3, which contain chlorido and nitrato ligands exhibit intense fluorescence blue emissions at 443 and 462 nm with quantum yields of 0.66 and 0.70, respectively. Although the complex Zn2 has the weakest emission in THF, it exhibited the strongest blue emission intensity in solid state. In addition, computational studies provided insights into the structural and electronic properties, showing a strong correlation with experimental data. The calculated absorption and emission spectra were promarily based on the transition between HOMO and LUMO (π-π*) with high oscillator strength.

BOATMAP: Bayesian Optimization Active Targeting for Monomorphic Arrhythmia Pace-mapping

Recent advances in machine learning and deep learning have presented new opportunities for learning to localize the origin of ventricular activation from 12-lead electrocardiograms (ECGs), an important step in guiding ablation therapies for ventricular tachycardia. Passively learning from population data is faced with challenges due to significant variations among subjects, and building a patient-specific model raises the open question of where to select pace-mapping data for training. This work introduces BOATMAP, a novel active learning approach designed to provide clinicians with interpretable guidance that progressively assists in locating the origin of ventricular activation from 12-lead ECGs. BOATMAP inverts the input–output relationship in traditional machine learning solutions to this problem and learns the similarity between a target ECG and a paced ECG as a function of the pacing site coordinates. Using Gaussian processes (GP) as a surrogate model, BOATMAP iteratively refines the estimated similarity landscape while providing suggestions to clinicians regarding the next optimal pacing site. Furthermore, it can incorporate constraints to avoid suggesting pacing in non-viable regions such as the core of the myocardial scar. Tested in a realistic simulation environment in various heart geometries and tissue properties, BOATMAP demonstrated the ability to accurately localize the origin of activation, achieving an average localization accuracy of 3.9±3.6mm with only 8.0±4.0 pacing sites. BOATMAP offers real-time interpretable guidance for accurate localization and enhancing clinical decision-making.

Copper Catalysts Anchored on Cysteine-Functionalized Polydopamine-Coated Magnetite Particles: A Versatile Platform for Enhanced Coupling Reactions

Cysteine plays a crucial role in the development of an efficient copper-catalyst system, where its thiol group serves as a strong anchoring site for metal coordination. By immobilizing copper onto cysteine-modified, polydopamine-coated magnetite particles, this advanced catalytic platform exhibits exceptional stability and catalytic activity. Chemical modification of the polydopamine (PDA) surface with cysteine enhances copper salt immobilization, leading to the formation of the Fe3O4@PDA-Cys@Cu platform. This system was evaluated in palladium-free, copper-catalyzed Sonogashira coupling reactions, effectively catalyzing the coupling of terminal acetylenes with aryl halides. Additionally, the Fe3O4@PDA-Cys@Cu platform was employed in click reactions, confirming the enhanced catalytic efficiency due to increased copper content. The reusability of the platform was further investigated, demonstrating improved performance, especially in recyclability tests in click reaction, making it a promising candidate for sustainable heterogeneous catalysis.

Synthesis of Ru‐PNPC Pincer Complexes and Applications in Catalytic Hydrogenation and Dehydrogenation Reactions

The reaction of N,N‐bis(2‐(diisopropylphosphaneyl)ethyl)prop‐2‐yn‐1‐amine 1 with [Ru(CO)ClH(PPh3)3] leads to the formation of a new class of cyclometallated PNPC pincer complexes. Several examples of this class of compounds are synthesized and characterized. They, specifically complexes 2 and 3, show good to excellent activity and selectivity in additive‐free formic acid dehydrogenation, and transfer (de)hydrogenation reactions of different functional groups (ketone, alkyne, alcohol). Theoretical and experimental studies reveal two competing pathways for the dehydrogenation of formic acid. The Ru‐H pathway proceeds via the coordination site trans to the propylene arm of the ligand, whereas in the Ru‐C pathway, a decoordination of the propylene arm is observed.

Synthesis, Electrochemistry and Density Functional Theory of Osmium(II) Containing Different 2,2′:6′,2″-Terpyridines

In coordination chemistry, 2,2′:6′,2″-terpyridine is a versatile and extensively studied tridentate ligand. Terpyridine forms stable complexes with a variety of metal ions through coordination sites provided by the three nitrogen atoms in its pyridine rings. This paper presents an electrochemical study on various bis(terpyridine)osmium(II) complexes, addressing the absence of a systematic investigation into their redox behavior. Additionally, a computational chemistry analysis was conducted on these complexes, as well as on eight previously studied osmium(II)-bipyridine and -phenanthroline complexes, to expand both the experimental and theoretical understanding. The experimental redox potentials, Hammett constants, and DFT-calculated energies show linear correlations due to the electron-donating or electron-withdrawing nature of the substituents, as described by the Hammett constants. These substituent effects cause shifts to lower or higher redox potentials, respectively.

Realizing Dual-Mode Zinc-Ion Storage of Generic Vanadium-Based Cathodes via Organic Molecule Intercalation.

Intercalation engineering is a promising strategy to promote zinc-ion storage of layered cathodes; however, is impeded by the complex fabrication routes and inert electrochemical behaviors of intercalators. Herein, an organic imidazole intercalation strategy is proposed, where V2O5 and NH4V3O8 (NVO) model materials are adopted to verify the feasibility of the imidazole intercalator in improving the zinc storage capabilities of vanadium-based cathodes. The intercalated imidazole molecules could not only expand interlayer spacing and strengthen structural stability by serving as extra "pillars" but also provide extra coordination sites for zinc storage via the coordination reaction between Zn2+ and the C═N group. This gives rise to a dual-mode ion storage mechanism and favorable electrochemical performances. As a result, imidazole-intercalated V2O5 delivers a capacity of 179.9 mAh g-1 after 5000 cycles at 20 A g-1, while the imidazole-intercalated NVO harvests a high capacity output of 170.2 mAh g-1 after 700 cycles at 2 A g-1. This work is anticipated to boost the application potentials of vanadium-based cathodes in aqueous zinc-ion batteries.

Skeleton design engineering of covalent organic frameworks to enable in situ incorporation of coordination sites for improved extraction of uranyl ions

The development of advanced porous materials for effectively separating uranium from nuclear wastewater or seawater is a highly coveted yet formidable task. However, the importance of the covalent organic frameworks (COFs) skeletons and the specific arrangement of adjacent atoms is often disregarded when configuring coordination settings for chelating molecules. In this study, a novel material for oxygen-enriched COFs was developed. The optimized oxygen-rich COFs showed aligned neighboring bonds and triazine groups along the skeletons, resulting in an increase in uranyl binding sites and a threefold rise in the total number of binding sites. The synergistic interaction of ether bonds and triazine groups in the π-conjugated skeletons significantly reduced the energy band gap, leading to improved uranium affinity and recovery. The adsorption capacity reached an impressive 660 mg/g, surpassing that of most COF-based adsorbents using a chemical coordination mechanism in uranium-containing aqueous solutions. This study provides valuable insights into designing novel adsorbents for uranium separation.

Evaluating a virtual facilitation workshop with antimicrobial stewardship teams within a cluster randomized stepped-wedge trial

BackgroundAntimicrobial stewardship programs (ASP) often function naturally as facilitators within clinical hospital settings, by working with individuals and teams to reduce unnecessary antibiotics. Within implementation science, facilitation has been studied and evaluated as an implementation strategy that can accelerate and improve fidelity to implementation efforts. This study describes a novel, virtual facilitation strategy developed and served as an intervention within the optimizing perioperative antibiotics for children trial (OPERATIC trial). This paper: (1) describes ASP team’s preferences for and use of a facilitation workshop and (2) describes sustained use of facilitation skills throughout the study period.MethodsStudy participants included antimicrobial stewardship team members from the nine children’s hospitals that participated in this study and completed facilitation training. All individuals who completed facilitation training were asked to evaluate the training through an online survey. Additionally, site leads were interviewed by the site coordinator every other month and asked about their team’s use of facilitation skills throughout the rest of the study period. Survey data were managed and coded in R, and qualitative interview data were analyzed using rapid methodology.Results30 individuals, including both physicians and pharmacists, completed the evaluation. Individuals largely rated themselves as novice facilitators (53%). Individuals reported satisfaction with virtual facilitation and identified different components of the workshops as valuable. An additional 108 interviews were performed throughout the study period. These interviews found that facilitators reported using all skills throughout the study period and described varied use of skills over time. All nine sites applied facilitation strategies, team building techniques, and communication/conflict skills at some point during the intervention phase.ConclusionWe describe the use of virtual facilitation as an acceptable and appropriate strategy to enhance facilitation skills for ASP teams working to reduce unnecessary postoperative antibiotics. Participants reported different useful components of facilitation training and described using differing facilitation skills throughout the trial. Overall, the use of facilitation skills continued throughout the duration of the study period. This paper outlines how facilitation training can be conducted virtually in a way that is feasible and acceptable to clinicians.Trial registrationNCT04366440, April 24, 2020.

Six-Membered Ring Directed Assembly of a Zirconium Zeolitic Metal-Organic Framework for Efficient Separation of Hexane Isomers.

The synthesis of zirconium MOFs with zeolite net is quite challenging due to the high connectivity of Zr6 clusters, which is far from tetrahedral connection, a requisite for zeolite net. In this work, we demonstrate a six-membered ring (6MR) strategy through mimicking of mineral zeolites with mixed ditopic and tritopic carboxylate linkers. With this strategy, the ditopic linker cross-links Zr6 clusters to form 4-connected zeolite-like nets, while the tritopic one is used to direct the formation of 6MR and simultaneously consumes extra coordination sites on the cluster. The feasibility of this strategy is shown by one zeolitic metal-organic framework (NNM-5) and this strategy has also led to the synthesis of the other dia-type zirconium MOF (NNM-6). Interestingly, as the tritopic linker not only directs the formation of 6MR but also partitions 6MR into small segments, NNM-5 with SOD topology shows a structural feature of small aperture and big cage, which has led to efficient separation of hexane isomers. With both exceptionally high n-hexane uptake (65.9 cm3 g-1) and size-exclusion selectivity, an exceptional separation capability is verified by breakthrough experiments. Calculation results demonstrate that the large difference of diffusion energy barrier due to the small aperture accounts for the underlying separation mechanism.

Performance of Cobalt-Doped C3N5 Electrocatalysis Nitrate in Ammonia Production

In this experiment, C3N5 was synthesized by pyrolysis of 3-amino-1,2,4 triazole material, and then 1% Co-C3N5, 3% Co-C3N5, 5% Co-C3N5, 7% Co-C3N5, and 9% Co-C3N5 were synthesized by varying the mass ratio of cobalt chloride to C3N5 by stirring and ultrasonic shaking. SEM, XPS, and XRD tests were performed on the synthesized materials. The experimental results showed that Co atoms were successfully doped into C3N5. The electrocatalytic reduction experiments were performed to evaluate their NH3 yields and electrochemical properties. The results showed that the ammonia yield obtained by the electrolysis of the 9% Co-C3N5 catalyst as the working electrode in a mixed electrolytic solution of 0.1 mol/L KNO3 and 0.1 mol/L KOH for 1 h at a potential of −1.0 V vs. RHE was 0.633 ± 0.02 mmol∙h−1∙mgcat−1, and the Faraday efficiency was 65.98 ± 2.14%; under the same experimental conditions, the ammonia production rate and Faraday efficiency of the C3N5 catalyst were 0.049 mmol∙h−1∙mgcat−1 and 16.41%, respectively, and the ammonia production rate of the C3N5 catalyst was nearly 13-fold worse than the 9% Co-C3N5, which suggests that Co can improve the Faraday efficiency and ammonia yield of the electrocatalytic reduction of NO3−. This is due to the strong synergistic effect between the cobalt and C3N5 components, with C3N5 providing abundant and homogeneous sites for nitrogen coordination and the Co-N species present in the material being highly efficient active sites. The slight change in current density after five trials of 9% Co-C3N5 and the decrease in ammonia yield by about 12% in five repetitions of the experiment indicate that 9% Co-C3N5 can be recycled and work stably in electrocatalytic reactions and has good application prospects.

Synthesis, Structures, and Properties for PIII-Doped Hetero-Buckybowls and Their Phosphonium Salts.

Doping polycyclic aromatic hydrocarbons with heteroatoms enables manipulation of their electronic structures. Herein, the structures and properties of phosphorus (P) doped heterosumanenes (HSEs) are regulated by varying the valence states of P-dopant. The phosphine sulfide (PV) and chalcogens (S, Se, Te) co-doped HSEs (1-3) are reduced to trivalent phosphorus (PIII) doped analogues 4-6. Then, the PIII-dopants on 4-6 are converted to phosphonium salts (R4P+), giving 7-9. The valence states of P-dopant show great influence on molecular geometries and electronic structures. Taking P and S co-doped HSEs as example, bowl-depths increase in the order of 1 (PV)<7 (R4P+)<4 (PIII), and the HOMO energy levels and HOMO-LUMO gaps increase to be 7<1<4. Consistent with the theoretical calculation, the first oxidation potentials decrease and the absorption/emission bands show blue shift from 7 to 1 to 4. The transformation of PV to PIII leads to large variations on the coordination with Ag+, owing to the alteration of coordination site from P=S to PIII. The phosphonium salts show ring-opening of phosphole rings under electrochemical reduction. It is found that chalcogen atoms play pivotal roles on coordination patterns of coordination complexes and the conversion rates of ring-opening reactions.

A tale of two old drugs tetracycline and salicylic acid with new perspectives—Coordination chemistry of their Co(II) and Ni(II) complexes, redox activity of Cu(II) complex, and molecular interactions

Extensive use of the broad-spectrum tetracycline antibiotics (TCs) has resulted their wide spread in the environment and drive new microecological balances, including the infamous antibiotic resistance. TCs require metal ions for their antibiotic activity and resistance via interactions with ribosome and tetracycline repressor TetR, respectively, at specific metal-binding sites. Moreover, the Lewis-acidic metal center(s) in metallo-TCs can interact with Lewis-basic moieties of many bioactive secondary metabolites, which in turn may alter their associated chemical equilibria and biological activities. Thus, it is ultimately important to reveal detailed coordination chemistry of metallo-TC complexes. Herein, we report (a) conclusive specific Co2+, Ni2+, and Cu2+-binding of TC revealed by paramagnetic 1H NMR, showing different conformations of the coordination and different metal-binding sites in solution and solid state, (b) significant metal-mediated activity of Cu-TC toward catechol oxidation with different mechanisms by air and H2O2 (i.e., mono- and di-nuclear pathways, respectively), (c) interactions of metallo-TCs with bioactive salicylic acid and its precursor benzoic acid, and (d) noticeable change of TC antibiotic activity by metal and salicylic acid. The results imply that TCs may play broad and versatile roles in maintaining certain equilibria in microecological environments in addition to their well-established antibiotic activity. We hope the results may foster further exploration of previously unknown metal-mediated activities of metallo-TC complexes and other metalloantibiotics.

The application of GIS technology in building a multivariate taphonomic profile for improving PMI estimations in Greece.

Environmental conditions highly affect decomposition rates and therefore a forensic practitioner should consider context-specific information when estimating the post mortem interval (PMI). Traditional methods of collecting environmental data, however, are time-consuming and often impractical for large-scale studies or routine forensic investigations. This study developed an automated computer method by employing the technology of geographic information systems (GIS) and Python programming language to provide contextual information for bodies found outdoors in Greece. The generated coding script underwent testing on 95 bodies in various stages of decomposition, which were examined between the years 1999 and 2022 at the National and Kapodistrian University of Athens and the Forensic Medical Service of Thessaloniki. Using ArcGIS Pro software and publicly available online data, a multilayer map was developed. Individual layers included high-resolution aerial images and data on the European Nature Information System ecosystem type, the Köppen-Geiger climatic type, the population density, the elevation, and the slope. Additionally, 99 national weather stations and their corresponding meteorological data were integrated. By leveraging the geographical coordinates of the recovery site of each case and information about the decedent's disappearance and recovery dates, this script automatically generates details from each of the above layers. Additionally, it calculates the accumulated degree days (ADD) and accumulated humidity days (AHD) values by extracting data from the nearest weather station. The GIS-based approach enables rapid, objective, and reproducible taphonomic profile construction, which can greatly improve the reliability of PMI estimations. By utilizing this method, forensic practitioners can accurately evaluate environmental effects on decomposition, thus standardizing taphonomic profiling globally.

Ce-doped NiCo-layered double hydroxide based self-supporting tremella-shaped nanoflower heterostructure as efficient electrocatalyst for the oxygen evolution reaction

NiCo-layered double hydroxide (NiCo-LDH) catalysts, which indicate a profound prospect of oxygen evolution reaction (OER) under alkaline conditions, are facing great challenges in terms of low electrical conductivity, restricted by poor conductivity, limited electrochemical reaction sites, and low-density of edge sites. The authors developed a simple and convenient in-situ one-pot self-assembly method. The Ce-doped defective NiCo-LDH hexagonal nanosheets and nitrogen-doped graphene fabricated the NiCoCe-LDH/RNF electrocatalyst on the nickel foam (NF) substrate, which demonstrated excellent OER activity under alkaline conditions, only needed 299 mV overvoltage to achieve 50 mA cm−2 current intensity, could last for 6 hours at 20 mA cm−2. The highly active OER benefited from the structural advantages of the novelty three-dimensional array structure. The novel geometric structure of tremella-shaped nanoflower integrated with curved nanosheets and curled edges loaded on NF provides more electrochemical reaction sites for intermediate coordination. The nitrogen-doped reduced graphene oxide accommodated better interaction between active materials and charge carriers, enhancing the conductivity and electron transfer performance of nanostructures. The effective synergistic between the heterostructures promoted the excellent OER electrocatalytic activity of NiFeCe-LDH/RNF nanocomposites. DFT calculations at the atomic level of pristine and Ce-doped NiCo-LDH exhibited that Ce-doping can reduce the Gibbs free energy of the potential-determining step and improve the catalytic activity of OER. This work has broadened the horizons for developing simple and highly available OER electrocatalysts.

A Computation-Guided Design of Highly Defined and Dense Bimetallic Active Sites on a Two-Dimensional Conductive Metal-Organic Framework for Efficient H2O2 Electrosynthesis.

Electrochemical synthesis of hydrogen peroxide (H2O2) via the two-electron oxygen reduction reaction (2e--ORR) provides an alternative method to the energy-intensive anthraquinone method. Metal macrocycles with precise coordination are widely used for 2e--ORR electrocatalysis, but they have to be commonly loaded on conductive substrates, thus exposing a large number of 2e--ORR-inactive sites that result in poor H2O2 production rate and efficiency. Herein, guided by first-principle predictions, a substrate-free and two-dimensional conductive metal-organic framework (Ni-TCPP(Co)), composed of CoN4 sites in porphine(Co) centers and Ni2O8 nodes, is designed as a multi-site catalyst for H2O2 electrosynthesis. The approperiate distance between the CoN4 and Ni2O8 sites in Ni-TCPP(Co) weakens the electron transfer between them, thus ensuring their inherent activities and creating high-density active sites. Meanwhile, the intrinsic electronic conductivity and porosity of Ni-TCPP(Co) further facilitate rapid reaction kinetics. Therefore, outstanding 2e--ORR electrocatalytic performance has been achieved in both alkaline and neutral electrolytes (>90 %/85 % H2O2 selectivity within 0-0.8 V vs. RHE and >18.2/18.0 mol g-1 h-1 H2O2 yield under alkaline/neutral conditions), with confirmed feasibility for water purification and disinfection applications. This strategy thus provides a new avenue for designing catalysts with precise coordination and high-density active sites, promoting high-efficiency electrosynthesis of H2O2 and beyond.

Supercapacitor electrodes based on Ru/RuO2 decorated on N,S-doped few-layer graphene

Innovatively designed flexible and high-performance shape memory polymer supercapacitors are promising next-generation energy storage devices for portable and wearable electronics. Therefore, thermally induced smart shape memory polymer polyurethane was synthesized using polycaprolactone/poly(ethylene glycol)/hexamethylene diisocyanate (PCL/PEG/HDI) in which the incorporation of PEG successfully assisted in lowering the transition temperature. The resulting polymer exhibits a remarkable transition temperature of 50 °C and a shape recovery ratio of 100 % at a strain of 300 %. The smart polymer was coated with a silver paste to ease the electron flow followed by coating with the electrode. Hybrid electrode materials are prepared in two stages. Initially, a few layers of holey-graphene were synthesized, where BET surface area reveals the presence of pores that are tuned by isothermal treatments in O2-atmosphere. Subsequently, active hybrid electrode materials nanostructured Ru/RuO2 decorated N, S-doped few layers of holey graphene were synthesized using hydrothermal methods. Here, nitrogen and sulfur doping in the basal or edge plane served as catalysts and metal coordination sites, facilitating the uniform distribution of ruthenium nanoparticles on the graphene. It is further confirmed by the density function theory (DFT) calculation using the adsorption energy. The optimized hybrid electrode material demonstrates a specific capacitance of 1297 mFcm−2 at a current density of 2 mAcm−2. A flexible-shape memory polymer supercapacitor exhibits a notable device-specific capacitance of 189 mFcm−2 at a current density of 1 mAcm−2, a high energy density of 45 µWhcm−2 at a power density of 0.25 mWcm−2, with 81 % of specific capacitance retention after eight shape programming and recovery cycle. Excellent shape recoverability and robust electrochemical performance make the as-fabricated symmetric supercapacitors a promising candidate for integration in flexible electronic applications.