Lower Electronegativity Research Articles

Insights into Hydrogen Bonding Effect as Well as Excited State Intramolecular Proton Transfer Associated with Solvent Polarity and Atomic Electronegativity for 2‐Phenyl‐3‐Hydroxybenzo[g]quinolone

AbstractInspired by the excellent photochemical properties of 3‐hydroxyflavone and its derivatives, in this work, the novel 2‐phenyl‐3‐hydroxybenzo[g]quinolone (2P3HBQ) fluorophore is explored about its photo‐induced behaviors. By investigating the photoexcitation characteristics in different solvents as well as the substituted atomic electronegativity (O→S→Se), the solvent‐polarity‐related and atomic‐electronegativity‐dependent photo‐induced hydrogen bond of 2P3HBQ and its derivatives (2P3HBQ‐O, 2P3HBQ‐S and 2P3HBQ‐Se) indicates the S1‐state hydrogen bonding interactions could be enhanced. Particularly, the nonpolar solvent environment and low atomic electronegativity substitution play large roles in strengthening hydrogen bonding effects. Charge reorganization stemming from photoexcitation, strengthening excited state hydrogen bond effects, and the intramolecular charge transfer (ICT) via frontier molecular orbitals (MOs) further reveals the excited state intramolecular proton transfer (ESIPT) tendency. Via the manner of constructing potential energy curves (PECs) with restricted optimization, we elaborate and reveal the novel solvent‐polarity‐regulated and the atomic‐electronegativity‐controlled ESIPT dynamical behaviors.

High-entropy transition metal disulfide colloid clusters: synergistic atomic scale interaction and interconnected network for ultra-stable potassium ion storage

High-entropy metal disulfide (HES2) colloid clusters were synthesized through a two-step templated solvothermal method for used as anode materials for potassium-ion storage devices. HES2’s large configuration entropy stabilizes its crystal structure and promotes chemical diversity by introducing multiple cations, thus reducing the impact of the shuttle effect, retaining active materials and extending cycling life up to 1800 cycles. During cycling, crystalline-amorphous grain boundaries formed in situ enhance electrochemical reaction activities and ensure the exposure of active sites. Elements with lower electronegativity allow S to bring more negative charges, improving the electrostatic force between S and K+ and enabling better anchoring of potassium polysulfide. Meanwhile, the retained close-packed cluster structure of HES2 provides a large contact area to accelerate the reduction reaction of the electrolyte in the sphere during the repeating K+ insertion/extraction. We further demonstrate the excellent performance of HES2 anodes on practical potassium-ion full battery and hybrid capacitor applications. The pioneering concept in atomic compositional engineering and structural design of transition metal sulfide electrodes presented in this work marks a significant step forward in the development of chalcogenide electrode systems for energy storage devices.

Three dimensional hollow sulphide nanocomposites for supercapacitor electrodes

The transition metal sulphides have gained sufficient attraction due to their high theoretical capacitance, low electronegativity, good thermal and electrical conductivity and good redox behaviour. In the present work, nanocomposites of nickel cobalt sulphide (NiCoS), zinc cobalt sulphide (ZnCoS), copper cobalt sulphide (CuCoS) and nickel-zinc-copper cobalt sulphide (NiZnCuCoS) have been prepared, by hydrothermal synthesis method, for their use as the supercapacitor electrode material. The X-ray diffraction analysis, Field Emission Scanning Electron Microscopy images and UV–Visible studies suggest the formation of quantum dots (as the crystallite size is in the range of 3.5 nm–6.0 nm) in all the nanocomposites. The aim of this study is to observe the change in the electrochemical properties of the transition metal sulphides by multi-metal doping. The electrochemical measurements reveal that among all the prepared nanocomposites, highest specific capacitance (150 F g−1 at 5 mV s−1) has been exhibited by CuCoS nanocomposites (nanowires like structure) whereas highest potential window (1.7 V) and hence highest energy density (16.5 W h kg−1 at 0.1 A g−1) has been exhibited by NiZnCuCoS nanocomposites. Presently, the main goal of supercapacitors is to provide high energy density. It is observed that multi-metal sulphides (NiZnCuCoS), when used as the supercapacitor electrode, provide better electrochemical performance which may be owing to the specific nanosheets like structures as well as good synergism between Ni, Zn, Cu and Co transition metals. Hence it is observed that by multi-metal doping, the supercapacitive behaviour of transition metal sulphides has improved.

Preparation of P-doped biochar and its high-efficient removal of sulfamethoxazole from water: Adsorption mechanism, fixed-bed column and DFT study

Heteroatom doping technology is of great significance for adsorption. However, the effect of P with relatively lower electronegativity (2.19) doped in the π-electron system and phosphorus-containing functional groups on the adsorption has always been neglected. Herein, P-doped biochar (PBC) was successfully synthesized via the in-situ activation method and applied in a bath experiment and a long-term fixed-bed dynamic adsorption for sulfamethoxazole (SMX) removal. Compared to pristine BC, the pHpzc, ash content and graphitization degree of PBC would be reduced significantly after phosphoric acid (H3PO4) was treated, but it gained a large specific surface area (SSA = 233 m2 g−1), as well as abundant surface functional groups. In the adsorption process, the behavior of SMX adsorbed onto PBC conformed to pseudo-second-order kinetic and Langmuir models in batch experiments. Its excellent adsorption capacity (148.62 mg g−1) benefited from a large number of functional groups. DFT calculation indicates that the C3-P-O configuration mainly promoted the adsorption of SMX. It is speculated that the hydrogen-bond interaction between SMX and C3-P-O was the main adsorption mechanism, and electrostatic and π-π EDA interaction also contributed. Various parameters during the dynamic process were thoroughly explored. The saturated adsorption capacity of the column would be promoted when influent SMX concentration and bed depth increased, but negatively correlated with solution pH and influent rate. Moreover, PBC fixed-bed column for SMX removal was well fitting Thomas, Yoon-Nelson and BDST models, which provided a predictable strategy for practical application.

Ca2+ doped metal organic frameworks for enhanced photocatalytic ammonia synthesis

Photocatalytic NH3 synthesis from N2 is a clean and sustainable approach, however, the efficiency of this process is low due to the difficult activation of NN triple bonds. Herein, we propose a metal-doping strategy to facilitate the interfacial charge transfer for promoting the photocatalytic NH3 yield. Ca2+ with low electronegativity was doped in UiO-66-NH2, a kind of Zr-based MOFs, to increase the electron donor capacity of Zr active sites. The X-ray photoelectron spectroscopy (XPS) spectra and density functional theory (DFT) calculations show that the Ca2+ doping enhances the electron density of Zr active sites. Moreover, the diamino ligand is incorporated to tune the bandgap structure of MOFs to expand its light absorption range. By adjusting the ratio of metals and organic ligands, the optimal photocatalyst UN(Zr-0.30Ca)-4 reaches a high NH3 evolution rate of 759.3 μmol g−1 h−1 under full spectrum. This study may provide some inspiration for the design of advanced photocatalysts for diverse chemical reduction reactions.

Insights into atomic‐electronegativity‐controlled excited state intramolecular proton transfer behavior for the novel oxazolonapthoimidazo[1,2‐a]‐pyridine (ONIP) compound: A time‐dependent density functional theory study

AbstractIn this work, we mainly focus on probing into the effects of atomic electronegativity on photo‐induced hydrogen bond (i.e., O–H···N) effects and excited state intramolecular proton transfer (ESIPT) processes for a novel fluorescent chemical probe ONIP derivatives (i.e., ONIP‐O, ONIP‐S, and ONIP‐Se). First, insights into optimized structural geometries and related infrared vibrational spectra, we clarify that the hydrogen bond O–H···N interaction could be strengthened via photoexcitation. Further, via predicting hydrogen bonding energy EHB, we quantificationally present that the S1‐state hydrogen bonding strengthening behavior should be more distinct with lower atomic electronegativity. When it comes to vertical photo‐induced excitation, the intramolecular charge transfer process happens and the charge redistribution plays roles in promoting ESIPT behavior. It is worth mentioning the energy gap between highest occupied molecular orbital and lowest unoccupied molecular orbital show that low atomic electronegativity should be more favorable to ESIPT process. Finally, based on the restricted optimization method, we construct the potential energy curves along with hydrogen bond wire for ONIP‐O, ONIP‐S, and ONIP‐Se. By exploring the conformation of potential energy curves and potential energy barriers, we disclose the detailed atomic‐electronegativity‐controlled ESIPT dynamical behaviors for ONIP system.

Selenium in Peptide Chemistry

In recent years, researchers have been exploring the potential of incorporating selenium into peptides, as this element possesses unique properties that can enhance the reactivity of these compounds. Selenium is a non-metallic element that has a similar electronic configuration to sulfur. However, due to its larger atomic size and lower electronegativity, it is more nucleophilic than sulfur. This property makes selenium more reactive toward electrophiles. One of the most significant differences between selenium and sulfur is the dissociation of the Se-H bond. The Se-H bond is more easily dissociated than the S-H bond, leading to higher acidity of selenocysteine (Sec) compared to cysteine (Cys). This difference in acidity can be exploited to selectively modify the reactivity of peptides containing Sec. Furthermore, Se-H bonds in selenium-containing peptides are more susceptible to oxidation than their sulfur analogs. This property can be used to selectively modify the peptides by introducing new functional groups, such as disulfide bonds, which are important for protein folding and stability. These unique properties of selenium-containing peptides have found numerous applications in the field of chemical biology. For instance, selenium-containing peptides have been used in native chemical ligation (NCL). In addition, the reactivity of Sec can be harnessed to create cyclic and stapled peptides. Other chemical modifications, such as oxidation, reduction, and photochemical reactions, have also been applied to selenium-containing peptides to create novel molecules with unique biological properties.

Theoretical insights into atomic-electronegativity-regulated ESIPT behavior for B-bph-fla-OH fluorophore

Inspired by the potential applications for detecting cysteine and the novel phototriggered CO release molecule (photoCORM) property, B-bph-fla-OH is explored in this work about its excited state behaviors. In view of significance of atomic electronegativity in photochemical reactions, we mainly focus on decoding photo-induced hydrogen bonding interactions and atomic-electronegativity-dependent excited state intramolecular proton transfer (ESIPT) behavior for Bbph-O, Bbph-S and Bbph-Se derivatives. Combining optimized geometrical changes and infrared (IR) stretching vibration related to hydrogen bond Oa-Hb···Oc, the photo-induced hydrogen bonding strengthening can be confirmed. Via predicting bond energy (EHB), we find low atomic electronegativity is in favor of enhancing hydrogen bonding interactions in both S0 and S1 states. Charge reorganization stemming from photoexcitation and atomic-electronegativity energy gap between HOMO and LUMO orbitals further reveals the ESIPT tendency. Insights into potential energy surfaces (PESs) and constructing energy profiles via searching transition state (TS) for Bbph-O, Bbph-S and Bbph-Se, we present the atomic-electronegativity-regulated ESIPT mechanism and spectral behaviors. We sincerely wish the specific and controlled excited state dynamical behavior could pave the ways for designing and developing novel fluorescent sensors based on B-bph-fla-OH derivatives in future.

Well-defined double hysteresis loop in NaNbO3 antiferroelectrics

Antiferroelectrics (AFEs) are promising candidates in energy-storage capacitors, electrocaloric solid-cooling, and displacement transducers. As an actively studied lead-free antiferroelectric (AFE) material, NaNbO3 has long suffered from its ferroelectric (FE)-like polarization-electric field (P-E) hysteresis loops with high remnant polarization and large hysteresis. Guided by theoretical calculations, a new strategy of reducing the oxygen octahedral tilting angle is proposed to stabilize the AFE P phase (Space group Pbma) of NaNbO3. To validate this, we judiciously introduced CaHfO3 with a low Goldschmidt tolerance factor and AgNbO3 with a low electronegativity difference into NaNbO3, the decreased cation displacements and [BO6] octahedral tilting angles were confirmed by Synchrotron X-ray powder diffraction and aberration-corrected scanning transmission electron microscopy. Of particular importance is that the 0.75NaNbO3−0.20AgNbO3−0.05CaHfO3 ceramic exhibits highly reversible phase transition between the AFE and FE states, showing well-defined double P-E loops and sprout-shaped strain-electric field curves with reduced hysteresis, low remnant polarization, high AFE-FE phase transition field, and zero negative strain. Our work provides a new strategy for designing NaNbO3-based AFE material with well-defined double P-E loops, which can also be extended to discover a variety of new lead-free AFEs.

Tuning the interface adhesion of Ag/ZnO composites by metallic dopants: A DFT study

Ag/ZnO composites have been widely applied in various fields, whilst their poor interface adhesion limits the integrative performance of these composites. Recently, metallic doping has been considered as a versatile strategy to tune the interface adhesion of metal/ceramic interfaces. However, the relationship between interface adhesion and electronic structure induced by doping at the Ag/ZnO interface needs to be further clarified. In this work, we investigated the work of separation (Wsep, value to estimate of interface adhesion), effective bond order and charge movement of Ag/ZnO interfaces with various dopants under four typical configurations by DFT calculations. It demonstrated that the dopants with lower electronegativity could enhance the interface adhesion of Ag/ZnO due to the interfacial Ag-O bonds with higher covalency level and shorter bond-lengths induced by larger charge transfer (Δq) and a higher degree of the p-d hybridization between the interfacial Ag and O atoms, while the dopants with higher electronegativity could weaken the interface adhesion. Moreover, we found that three atomic parameters (bond-lengths, <AEBO>-the average of effective bond order, Δq) were able to quantitatively rationalize the Wsep. This work advances the understanding of doping effect on the interface adhesion of Ag/ZnO interfaces that can be extended to other metal/ceramic interfaces.

Controlling the Photocatalytic Activity and Benzylamine Photooxidation Selectivity of Bi2WO6 via Ion Substitution: Effects of Electronegativity

Doping or ion substitution is often used as an effective strategy to improve photocatalytic activities of several semiconductors. Most frequently, the dopants provide extra states to increase light absorption, alter the electronic structure, or lower the carrier recombination. This work focuses on ion substitution in Bi2WO6, where the dopants modify band-edge potentials of the catalysts. Specifically, we investigate how the electronegativity (EN) of the dopant could be used to tune the band-edge potentials and how such changes influence the photocatalytic mechanism. Compared to Te that has a lower EN, I lowers the band-edge potentials. While substitutions with both ions enhance Rh B photodegradation and benzylamine photooxidation, the modified band potentials of I-doped Bi2WO6 influence the benzylamine photooxidation pathway, resulting in higher selectivity. Additionally, substitution of I7+ in the Bi2WO6 lattice improves the morphologies, decreases the band-gap energy, and reduces the carrier recombination. As a result, I-doped Bi2WO6 shows almost 3 times higher %conversion while maintaining 100% selectivity in the oxidative coupling of benzylamine. The findings here signify the importance of the choices of dopants on the photocatalytic reactions and would benefit the design of other related materials for such applications.

Dual-reaction center catalyst based on common metals Cu-Mg-Al for synergistic peroxymonosulfate adsorption-activation in Fenton-like process

To improve the peroxymonosulfate (PMS) utilization and the catalyst stability, a dual-reaction center catalyst, Cu-Mg0.388Al2.408O4-BN, was fabricated free of expensive rare metals. The presence of Mg leads to a positive-charged surface that was highly favorable for adsorbing bisphenol A (BPA) and PMS anions under neutral pH conditions. The relatively low electronegativity of Mg, together with the electronic compensation of cation-π between Cu and boron nitride (BN), resulted in the formation of the electron-rich Cu center. The combination of the electrostatic attraction and dual-reaction center led to the rapid degradation of BPA via a fast electron transfer step from BPA to the electron-rich Cu center, and then to PMS for effective activation. This unique design renders excellent reusability and stability of the catalyst by avoiding the redox cycle of Cu(I)/Cu(II). This research work opens new horizons to use common metals for efficient activation of PMS as economical alternatives over expensive rare metal catalysts in Fenton-like processes.

Tailoring the electronic structure of ZnCo2O4 by incorporating anions with low electronegativity to improve the water oxidation activity

Electron configurations and conductivity are significant descriptors/characteristics for the oxygen evolution reaction (OER), which can be modulated with heteroatom doping. Given that metal substitution usually reduces the number of active sites of spinel electrocatalysts, the effect of anion doping on the electronic structure has been investigated by using ZnCo2O4 (ZCO) as a demonstration. Compared with Co3+-dominated ZCO, the substitution of oxygen with less electronegative sulfur raises the portion of Co2+ in the low-spin states (t2g6eg1), which is more OER-active than Co3+ (t2g6eg0). Co2+ in the sulfur-doped ZCO (ZCO-S) is associated with the redistribution of electron density from S toward Co due to the high covalent interaction of Co—S. The Co—S interaction also induces a fast charge transfer. ZCO-S outperforms pristine ZCO by 11 times in terms of specific OER activity at 1.65 V versus reversible hydrogen electrode. In contrast, doping fluorine with higher electronegativity and valence deteriorates OER activity. Our work establishes the correlation between the electronegativity of anion dopants and OER intrinsic activity in spinel oxides and provides a simple and effective method to modulate the electronic structure of spinel oxides by doping anions with different electronegativities, which can be a new avenue for the rational design of high-performance spinel electrocatalysts.

Hierarchal Growth of Integrated n-MoS2/p-Black Phosphorus Heterostructures for All-Solid-State Asymmetric Supercapacitor Electrodes

MoS2 has gained more interest among two-dimensional (2D) materials due to its large surface area and low electronegativity, making it an ideal electrode material for supercapacitors. The Low intrinsic conductivity and agglomeration induced by the van der Waals interaction of MoS2 continue to impair its supercapacitive performance. To address this sluggish electrochemical performance, we synthesized an n-p-type MoS2/BP heterostructure adopting a facile hydrothermal approach and examined its electrochemical performance for the first time. An all-solid-state asymmetric supercapacitor with MoS2/BP as the negative electrode and VS2/BP as the positive electrode was constructed to evaluate the material’s electrochemical performances. The proposed all-phosphorene-based device demonstrated exceptional capacitance retention and cyclic stability, with a capacitance of around 114 F g–1 at a current density of 4 A g–1 and an energy/power density of 34.71 Wh kg–1/4031 W kg–1.

NiCo2S4 combined 3D hierarchical porous carbon derived from lignin for high-performance supercapacitors

Metal sulfides with the nature of low electronegativity and high electrochemical activity are potentially considered effective electrode materials for supercapacitors. Meanwhile, hierarchical porous carbon (HPC) materials derived from eco-friendly enzymatic hydrolysis lignin are the ideal matrix for holding nanoparticles (NP) that allows the overall NP/HPC composite to achieve outstanding electrochemical performance. In this study, NiCo2S4 nanoparticles were in-situ synthesized on the inner surface of 3D HPC that derived from enzymatic hydrolysis lignin with a simple one-step solvothermal method, thus forming a high-performance composite electrode material for supercapacitor applications. As a result, the NiCo2S4/HPC composite yields an outstanding specific capacity of 1264.2 F g−1 at 1 A g−1 and also exhibits remarkable rate performance. Such remarkable property is attributed to the effective combination of NiCo2S4 plus HPC and their strong chemical bonds, which enable excellent electronic conductivity and abundant exposed electroactive sites. The asymmetric supercapacitor assembled by utilizing NiCo2S4/HPC and active carbon as the positive and negative electrodes, respectively, provide an excellent energy density of 32.05 Wh kg−1 at a power density of 193.9 W kg−1. This work puts forward a practical optimization strategy for metal sulfides used in electrochemical energy storage devices.

The influence of oxygen and electronegativity on iron mineral chemistry throughout Earth’s history

The mineral record contains chemical signatures that reflect the evolving redox conditions of Earth’s crust, and reveal trends in the bioavailability of life's critical elements. In particular, shifting redox states of transition metal elements that are used as co-factors by enzymes across all domains of life can be tracked in preserved mineral chemistry. The transition metal iron (Fe) is one of the most abundant elements in Earth’s core, mantle, and crust, and is commonly a major constituent of rock-forming minerals. Additionally, Fe is the most widely used metal in biology, and Earth’s redox history has profoundly impacted the chemical speciation and availability of Fe in aqueous systems. The diverse mineral chemistry of Fe can therefore reveal new insights into the redox evolution of Earth’s crust and subsequent biological impacts. Here, we apply a new mineral chemistry network analysis platform, dragon, to investigate the mineral chemistry of iron (Fe) over geologic-time. We present bipartite network graphs of iron minerals linked to their constituent elements or ions for several geological time intervals. These graphs illustrate the increasing importance of oxygen (O) abundance in the atmosphere from the Paleoarchean to the Mesoproterozoic in regard to the the emergence of new Fe minerals, as well as the influence of free O on trends in element electronegativity in mineral formation and electron transfer processes. The proportion of oxygen containing Fe minerals had the sharpest increase during the time periods of the Kenorland and Columbia supercontinent assembly events. Indeed, the rise of O is associated with O becoming more centralized in the network as well as with an increase through time in the number of Fe minerals containing combinations of high and low electronegativity elements. The importance of oxygen in the expansion of Fe mineral chemical diversity, and its influence on the bioavailability of Fe in the environment, is illustrated clearly in the Fe mineral chemistry network.

Diverse CsPbI3 assembly structures: the role of surface acids.

Surface ligand engineering, seed introduction and external driving forces play major roles in controlling the anisotropic growth of halide perovskites, which have been widely established in CsPbBr3 nanomaterials. However, colloidal CsPbI3 nanocrystals (NCs) have been less studied due to their low formation energy and low electronegativity. Here, by introducing different molar ratios of surface acids and amines to limit the monomer concentration of lead-iodine octahedra during nucleation, we report dumbbell-shaped CsPbI3 NCs obtained by the in situ self-assembly of nanospheres and nanorods with average sizes of 89 nm and 325 nm, respectively, which showed a high photoluminescence quantum yield of 89%. Structural and surface state analyses revealed that the strong binding of benzenesulfonic acid promoted the formation of a Pb(SO3-)x-rich surface of CsPbI3 assembly structures. Furthermore, the addition of benzenesulfonic acid increases the supersaturation threshold and the solubility of PbI2 in a high-temperature reaction system, and controls effectively the lead-iodine octahedron monomer concentration in the second nucleation stage. As a result, the as-synthesized CsPbI3-Sn NCs exhibited different assembly morphologies and high PLQYs, among which the role of sulfonate groups can be further verified by UV absorption and surface characteristics. The strategy provides a new frontier to rationally control the surface ligand-induced self-assembly structures of perovskites.

Solving Strength-Toughness Dilemma in Superhard Transition-Metal Diborides via a Distinct Chemically Tuned Solid Solution Approach.

Solid solution strengthening enhances hardness of metals by introducing solute atoms to create local distortions in base crystal lattice, which impedes dislocation motion and plastic deformation, leading to increased strength but reduced ductility and toughness. In sharp contrast, superhard materials comprising covalent bonds exhibit high strength but low toughness via a distinct mechanism dictated by brittle bond deformation, showcasing another prominent scenario of classic strength-toughness tradeoff dilemma. Solving this less explored and understood problem presents a formidable challenge that requires a viable strategy of tuning main load-bearing bonds in these strong but brittle materials to achieve concurrent enhancement of the peak stress and related strain range. Here, we demonstrate a chemically tuned solid solution approach that simultaneously enhances hardness and toughness of superhard transition-metal diboride Ta1-x Zr x B2. This striking phenomenon is achieved by introducing solute atom Zr that has lower electronegativity than solvent atom Ta to reduce the charge depletion on the main load-bearing B-B bonds during indentation, leading to prolonged deformation that gives rise to notably higher strain range and the corresponding peak stress. This finding highlights the crucial role of properly matched contrasting relative electronegativity of solute and solvent atoms in creating concurrent strengthening and toughening and opens a promising avenue for rational design of enhanced mechanical properties in a large class of transition-metal borides. This strategy of concurrent strength-toughness optimization via solute-atom-induced chemical tuning of the main load-bearing bonding charge is expected to work in broader classes of materials, such as nitrides and carbides.

Sustainable and Scalable Approach for Enhancing the Electrochemical Performance of Molybdenum Disulfide (MoS2)

Molybdenum disulfide (MoS2), the second most thoroughly investigated two-dimensional material after graphene, has attracted considerable interest in energy storage applications owing to its exceptional qualities, including its unique crystal structure, low electronegativity, and high specific capacity. In this study, we showed that a simple ball-milling procedure causes significant improvement in the capacitive properties of the bulk MoS2 (BL-MoS2). We characterized the material before and after the milling process using X-ray diffraction (XRD) and a BET surface area analyzer to find the material’s structural, crystalline features, and surface area, respectively. We prepared electrodes of BL-MoS2 and ball-milled MoS2 (BM-MoS2) for electrochemical investigation. The charge storage characteristics were examined using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The BM-MoS2 and BL-MoS2 have a specific capacitance of 114 F/g and 96 F/g, respectively.

Electron promoted palladium-cobalt active sites for efficient catalytic combustion of methane

Catalytic combustion of methane is a promising technology to abate unburnt methane from the expanding natural gas industry, and the catalytic performance depends on the electronic structure of active sites. Herein, designated dopants (yttrium, magnesium, zinc, nickel, or tin) with different electron affinity were facilely incorporated into alumina supported palladium-cobalt catalysts (Pd/C-A) to realize the efficient methane combustion. The incorporation of dopants effectively tuned the microstructure, surface property and electronic state of catalysts, and their catalytic activity showed an inverted volcano trend with the increased electronegativity of dopants. The Mg dopant with a relatively low electronegativity provided additional electrons to participate in the Pd–Co interaction, which not only increased the ratio of active Pd4+ and Co2+ species, but also promoted the conversion of Pd↔PdOx and depressed the accumulation of –OH species. Consequently, the Mg doped catalyst presented a remarkably higher catalytic activity, stability and water-resistance than Pd/C-A. The proposed electron modification strategy can be further extended to rationally screen dopants and construct active sites for catalytic applications.