Boosting Thermal and Mechanical Properties: Achieving High-Safety Separator Chemically Bonded with Nano TiN Particles for High Performance Lithium-Ion Batteries.

Currently, the commercial separator (Celgard2500) of lithium-ion batteries (LIBs) suffers from poor electrolyte affinity, mechanical property and thermal stability, which seriously affect the electrochemical performances and safety of LIBs. Here, the composite separators named PVDF-HFP/TiN for high-safety LIBs are synthesized. The integration of PVDF-HFP and TiN forms porous structure with a uniform and rich organic framework. TiN significantly improves the adsorption between PVDF-HFP and electrolyte, causing a higher electrolyte absorption rate (192%). Meanwhile, XPS results further demonstrate the tight link between PVDF-HFP and TiN due to the existence of TiF bond in PVDF-HFP/TiN, resulting in a strong impediment for the puncture of lithium dendrites as a result of the improved mechanical strengths. And PVDF-HFP/TiN can effectively suppress the growth of lithium dendrites by means of uniform lithium flux. In addition, the excellent heat resistance of TiN improves the thermal stability of PVDF-HFP/TiN. As a result, the LiFePO4 ||Li cells assembled PVDF-HFP/TiN-12 exhibit excellent specific capacity, rate performance, and capacity retention rate. Even the high specific capacity of 153 mAh g-1 can be obtained at the high temperature of 80 °C. Meaningfully, a reliable modification strategy for the preparation of separators with high safety and electrochemical performance in LIBs is provided.

Photocatalytic Oxidative Coupling of Methane over Au1 Ag Single-Atom Alloy Modified ZnO with Oxygen and Water Vapor: Synergy of Gold and Silver.

C-H dissociation and C-C coupling are two key steps in converting CH4 into multi-carbon compounds. Here we report a synergy of Au and Ag to greatly promote C2 H6 formation over Au1 Ag single-atom alloy nanoparticles (Au1 Ag NPs)-modified ZnO catalyst via photocatalytic oxidative coupling of methane (POCM) with O2 and H2 O. Atomically dispersed Au in Au1 Ag NPs effectively promotes the dissociation of O2 and H2 O into *OOH, promoting C-H activation of CH4 on the photogenerated O- to form *CH3 . Electron-deficient Au single atoms, as hopping ladders, also facilitate the migration of electron donor *CH3 from ZnO to Au1 Ag NPs. Finally, *CH3 coupling can readily occur on Ag atoms of Au1 Ag NPs. An excellent C2 H6 yield of 14.0 mmol g-1 h-1 with a selectivity of 79 % and an apparent quantum yield of 14.6 % at 350 nm is obtained via POCM with O2 and H2 O, which is at least two times that of the photocatalytic system. The bimetallic synergistic strategy offers guidance for future catalyst design for POCM with O2 and H2 O.

Local Photothermal Effect Enabling Ni3 Bi2 S2 Nanoarray Efficient Water Electrolysis at Large Current Density.

In terms of the large-scale hydrogen production by water electrolysis, achieving the bifunctional electrocatalyst with high efficiency and stability at high current densities is of great significance but still remains a grand challenge. To address this issue, herein, one unique hybrid electrode is synthesized with the local photothermal effect (LPTE) by supporting the novel ternary nickel (Ni)bismuth (Bi)sulfur (S) nanosheet arrays onto nickel foam (Ni3 Bi2 S2 @NF) via a one-pot hydrothermal reaction. The combined experimental and theoretical observations reveal that owing to the intrinsic LPTE action of Bi, robust phase stability of Ni3 Bi2 S2 as well as the synergistic effect with hierarchical configuration, upon injecting the light, the as-prepared Ni3 Bi2 S2 exhibits remarkably improved efficiency of 44% and 35% for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Such enhanced values are also comparable to those performed in working media heated to 80 °C. In addition, the overall water splitting system by using Ni3 Bi2 S2 @NF as bifunctional electrodes only delivers an ultralow voltage of 1.40 V at 10 mA cm-2 under LPTE, and can be stable more than 36 h at 500-1000 mA cm-2 . More broadly, even worked at 0-5 °C, alkaline simulated seawater and high salt seawater, the electrodes still show apparent LPTE effect for improving catalytic efficiency.

Effects of a Pd/Pt bimetal supported by a γ-Al2O3 surface on methane activation.

The catalytic removal of methane (CH4) in exhaust emissions of natural gas-fueled vehicles is still a major challenge for automotive manufacturers because of the high CH3-H bond energy and high concentrations of water (H2O). Density functional theory (DFT) calculations were employed to investigate the adsorption of CH4 and H2O, as well as the activation of CH4, on the surface of a Pd-Pt bimetal supported by γ-Al2O3. These are significant factors for catalytic combustion. Pt addition weakened the bonding of the intermediates and increased the availability of electrons on the surface. Besides this, the γ-Al2O3 surface and Pt were both beneficial for preventing the aggregation of clusters. CH4 and H2O adsorption, as well as the detailed mechanism of CH4 activation on the Pd-Pt/γ-Al2O3 surfaces were simulated. The results showed that a Pt/Pd ratio of three resulted in the best catalytic activity among the different ratios examined in the presence of H2O.

Azobenzene-Bridged Expanded "Texas-sized" Box: A Dual-Responsive Receptor for Aryl Dianion Encapsulation.

We report an expanded "Texas-sized" molecular box (AzoTxSB) that incorporates photoresponsive azobenzene bridging subunits and anion recognition motifs. The shape of this box can be switched through light induced E ↔ Z photoisomerization of the constituent azobenzenes. This allows various anionic substrates to be bound and released by using different forms of the box. Control can also be achieved using other environmental stimuli, such as pH and anion competition.

Synergetic promotion by oxygen doping and Ca decoration on graphene for CO2 selective adsorption.

The selective adsorption of CO2 by alkali earth metal (AEM)-decorated double vacancy graphene (DVG) was investigated with the first principles method. It is found that Be, Ca, Sr and Ba can be anchored stably on the DVG (whereas Mg cannot), and the Ca-decorated sample (Ca_DVG) possesses the strongest CO2 adsorption with a heat release of -0.45 eV per CO2. Furthermore, the doping of oxygen atoms on Ca_DVG (denoted as Ca_PyODVG) can remarkably increase the adsorption energy to -0.74 eV per CO2. This considerable promotion is ascribed to a synergetic effect of Ca decoration and O doping, which boosts extra electrons to transfer from the Ca_PyODVG substrate to the adsorbed CO2 molecule via the Ca 3p-O 2s hybridization. Notably, the obtained Ca_PyODVG is demonstrated to have a more practical CO2 desorption temperature, as well as a broader window for the selective adsorption of CO2 over CH4 and H2. Our theoretical results imply that Ca_PyODVG should be a promising candidate for CO2 capture. Additionally, the adsorption energy of CO2 is linearly correlated to the work function of a substrate, which may be used to accelerate the experimental screening of promising adsorbents.

Double graphitic-N doping for enhanced catalytic oxidation activity of carbocatalysts.

Graphitic N (GrN) doping is an effective way to promote the catalytic oxidation activities of pristine graphene, but a low doping density still limits its practical use. Based on DFT calculations, a double graphitic N (GrN) doping method is proposed. When the two GrN atoms are located at two different but nearby hexatomic rings, the dissociation of O2 molecules is significantly facilitated and the subsequently formed oxygen groups remain active for SO2 oxidation. In contrast, if the two GrN atoms are located at the same hexatomic rings of graphene, sluggish carbonyl groups will be formed in spite of the dissociation of O2 molecules being extraordinarily preferred.

A computational study of supported Cu-based bimetallic nanoclusters for CO oxidation.

In this study, we used DFT calculations to investigate the bi-functional nature of Cu-based alloy nanoclusters (NCs) supported on CeO2(111) for CO oxidation. More specifically, we studied the reaction pathways on Cu3Pt7 and Cu3Rh7via the O2 associative (OCOO) and dissociative mechanisms. We find that CO oxidation on Cu3Pt7 proceeds via the O2 dissociation pathway, while Cu3Rh7 prefers the OCOO mechanism. Combined with our previous results on Cu3Au7, we find that bi-functional CO oxidation on Cu-based alloys follows a Brønsted-Evans-Polanyi relationship, which provides a useful metric for the design of bi-functional alloyed catalysts.

Highly Efficient Performance and Conversion Pathway of Photocatalytic NO Oxidation on SrO-Clusters@Amorphous Carbon Nitride.

This work demonstrates the first molecular-level conversion pathway of NO oxidation over a novel SrO-clusters@amorphous carbon nitride (SCO-ACN) photocatalyst, which is synthesized via copyrolysis of urea and SrCO3. The inclusion of SrCO3 is crucial in the formation of the amorphous carbon nitride (ACN) and SrO clusters by attacking the intralayer hydrogen bonds at the edge sites of graphitic carbon nitride (CN). The amorphous nature of ACN can promote the transportation, migration, and transformation of charge carriers on SCO-ACN. And the SrO clusters are identified as the newly formed active centers to facilitate the activation of NO via the formation of Sr-NOδ(+), which essentially promotes the conversion of NO to the final products. The combined effects of the amorphous structure and SrO clusters impart outstanding photocatalytic NO removal efficiency to the SCO-ACN under visible-light irradiation. To reveal the photocatalytic mechanism, the adsorption and photocatalytic oxidation of NO over CN and SCO-ACN are analyzed by in situ DRIFTS, and the intermediates and conversion pathways are elucidated and compared. This work presents a novel in situ DRIFTS-based strategy to explore the photocatalytic reaction pathway of NO oxidation, which is quite beneficial to understand the mechanism underlying the photocatalytic reaction and advance the development of photocatalytic technology for environmental remediation.

Influence of Hf Doping on the Oxygen Behaviors on ZrCo(110) Surface Using First-Principles Calculation.

ZrCo alloy is easily poisoned by impurity gases such as O2, CO, and CO2, resulting in a deterioration in hydrogen storage performance. In this study, we conducted a comprehensive investigation into the adsorption and dissociation characteristics of oxygen on the ZrCo(110) surface using first-principles calculations. Previous studies indicated that the anti-disproportionation properties of ZrCo alloy can be significantly improved by Hf substitution, but the effect of Hf doping on the anti-poisoning properties has not been reported. We also examined the effect of Hf doping on the adsorption, dissociation, and diffusion characteristics of oxygen. It is found that on the ZrCo(110) surface, O2 molecules are easily dissociated and then stably adsorbed at the hollow site. Oxygen atoms will fill the surface preferentially and then diffuse inward. The doping of Hf has an insignificant impact on the adsorption or dissociation behavior of oxygen in comparison to the pure ZrCo surface. However, a notable observation is that the doping of Hf resulted in a reduction in the diffusion barrier for oxygen from the surface to the subsurface by 0.61 eV. Consequently, our study suggests that doping Hf is not an advisable strategy for improving the ZrCo(110) surface's resistance to O2 poisoning because of improved oxygen permeability.

Interfacial chemistries in metal-organic framework (MOF)/covalent-organic framework (COF) hybrids.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been attracting tremendous attention in various applications due to their unique structural properties. Recent interest has been focused on their combination as hybrids to enable the engineering of new classes of frameworks with complementary properties. This review gives a comprehensive summary on the interfacial chemistries in MOF/COF hybrids, which play critical roles in their hybridization. The challenges and perspectives in the field of MOF/COF hybrids are also provided to inspire more efforts in diversifying this hybrid family and their cross-disciplinary applications.

Directed regulation mechanism on chlorine substitution of PCDD/Fs isomers based on quantum chemical computation.

BACKGROUND: Chlorine substitution has been considered as one of the key steps of polychlorinated dibenzodioxin/furan (PCDD/Fs) generation. The introduction of oxygen carriers (OCs), especially in chemical looping combustion (CLC), provides the platform of directed regulation for the chlorine substitution process. METHODS: Density functional theory (DFT) calculations with code VASP 5.4 were employed to investigate the free energy of PCDD/Fs adsorption on different surfaces. 12378-PCDD, which is the product of a one-step chlorine substitution for toxic 2378-PCDD, has been selected as the calculation case, and the regulation mechanisms on the inter-isomeric conversion of 12378-PCDD were identified by calculating the energy barrier and action angle. RESULTS: It was found that the chlorine substitution of 12378-PCDD, particularly in 4# position, 9# position, and 6# position, emerged a tendency to increase the difficulty in turn, which conforms to the principle of distal preference. Besides, the influence from CaO adsorption on the crystalline surface of the iron-based oxygen carrier (OC) has been analyzed and it was verified that CaO adsorption can significantly increase the energy barrier for the chlorine substitution of 12378-PCDD. Meanwhile, the action angle was proposed to evaluate the parameters of adsorption process, and the adsorption of CaO can not only change the action angle between the 12378-PCDD molecule and the lattice surface, but also can modulate the energy barrier order of chlorine substitution among PCDD isomers. In addition, the loading component modulation was carried out to further confirm the feasibility of modulating the chloride substitution pathway, which proved the influence degree of loading component. And accordingly, the stretching analysis of the inactive component provides a theoretical basis for the subsequent study of the directional regulation of the PCDDs isomer generation pathway. Finally, the chlorine substitution rules and directed regulation mechanisms of PCDD/Fs isomers were obtained, which provides a modification direction for the structural components of OCs.

Accelerating structure reconstruction to form NiOOH in metal-organic frameworks (MOFs) for boosting the oxygen evolution reaction.

Structural reconstruction of electrocatalysts to generate metal hydroxide/oxyhydroxide species is critical for an efficient oxygen evolution reaction (OER), but the controllable regulation of the reconstruction process still remains a challenge. Given the designable nature of metal-organic frameworks (MOFs), herein, we have reported a localized structure disordering strategy to accelerate the structural reconstruction of Ni-BDC to generate NiOOH for boosting the OER. The Ni-BDC nanosheets were modified by Fe3+ and urea to form cracks, which could promote the accessibility of the Ni sites by the electrolyte and thus promote the reconstruction to form NiOOH. In addition, the interaction between Ni2+ and Fe3+ allows the electron flow from Ni2+ to Fe3+, further enhancing the NiOOH generation. As a result, the optimized sample exhibits excellent OER activity with a small overpotential of 251 mV at 10 mA cm-2, which is superior to most of the MOF-based OER catalysts reported previously. This work provides a controllable strategy to regulate the structural reconstruction for promoting the OER, which could provide important guidance for the development of more efficient OER electrocatalysts.

A theoretic insight into the catalytic activity promotion of CeO2 surfaces by Mn doping.

In this paper, we investigated the primary reduction and oxygen replenishing processes over Mn substitutionally doped CeO(2)(111) surfaces by density functional theory with the on-site Coulomb correction (DFT + U). The results indicated that Mn doping could make the surface much more reducible and the adsorbed O(2) could be effectively activated to form superoxo (O(2)(-)) and/or peroxo species (O(2)(2-)). The Mn doping induced the Mn 3d-O 2p gap state instead of Ce 4f acting as an electrons acceptor and donor during the first oxygen vacancy formation and O(2) replenishing, which helped to lower the formation energy of the first and second oxygen vacancies to -0.46 eV and 1.40 eV, respectively. In contrast, the formation energy of a single oxygen vacancy in the pure ceria surface was 2.08 eV and only peroxo species were identified as the O(2) molecule adsorbed. Our work provides a theoretical and electronic insight into the catalytic redox processes of Mn doped ceria surfaces, which may help to understand the enhanced catalytic performances of MnO(x)-CeO(2) oxides, as reported in previous experimental works.

Nitrogen/oxygen codoped hierarchical porous Carbons/Selenium cathode with excellent lithium and sodium storage behavior.

A nitrogen/oxygen codoped carbon derived from sweet potato (SPC) with interconnected micro-mesopores is applied to encapsulate selenium composite (SPC/Se) with a high Se loading (74.3%). As a cathode for advanced Li-Se and Na-Se batteries, the SPC/Se exhibits superior electrochemical behavior in low-cost carbonate electrolyte. Including the hierarchically porous structure of SPC and the chemical bonding between Se and carbon, the strong binding energy between SPC and Li2Se/Na2Se is also proved by DFT method, which results in the effective mitigation of shuttle reaction and volume change for SPC/Se cathode. For Li-Se batteries, the SPC/Se composite shows the initial specific charge capacity of 668 mAh g-1 with a high initial coulombic efficiency of 78%, and maintains a stable reversible capacity of 587 mAh g-1 after 1000 cycles with a weak capacity decay of 0.082% at 0.2C. It still retains a reversible specific capacity of 375 mAh g-1 even at 20C. For Na-Se battery, the SPC/Se composite displays the initial specific charge capacity of 671 mAh g-1 at 0.2C and maintains a reversible specific capacity of 412 mAh g-1 after 500 cycles with a capacity retention of 61.4%. When the current density increases to 20C, it still delivers a high reversible specific capacity of 420 mAh g-1. Finally, the transformation mechanism of Se molecule is illustrated detailedly in (de)lithi/sodiation process.

Uniform H-CdS@NiCoP core-shell nanosphere for highly efficient visible-light-driven photocatalytic H2 evolution.

Constructing highly efficient and cost-effective photocatalyst system has been a big challenge for photocatalysis. Herein, CdS nanosphere (N-CdS), hollow CdS (H-CdS) and a series of H-CdS@NiCoP core-shell nanospheres have been successfully prepared via a facile hydrothermal method. The activity test showed that H-CdS exhibited higher photocatalytic activity (3.34 mmol g-1h-1) compared with N-CdS (0.99 mmol g-1h-1) under visible light irradiation (λ ≥ 420 nm), suggesting that hollow structure could effectively improve photocatalytic activity. Moreover, the H-CdS@NiCoP-7 wt% displayed a maximum photocatalytic H2 evolution rate of 13.47 mmol g-1h-1, which was about 4 times and 2.5 times higher than that of pristine H-CdS and H-CdS@Pt-3 wt%, respectively. Furthermore, H-CdS@NiCoP-7 wt% exhibited a good stability during 20 h test. The physicochemical properties were characterized by XRD, SEM, TEM, XPS, UV-vis DRS, PL and photoelectrochemical technique. The results showed that NiCoP addition can construct p-n junction with H-CdS and effectively promote the charge transfer from CdS to NiCoP, which improved the photocatalytic hydrogen evolution activity. This work revealed that NiCoP could react as an excellent co-catalyst for enhancing H-CdS photocatalytic activity.

Thermal activation significantly improves the organic pollutant removal rate of low-grade manganese ore in a peroxymonosulfate system.

Low-cost, eco-friendly and effective catalysts are essential for activating peroxymonosulfate (PMS) to purify water. Hence, we investigated using thermal activation natural low-grade manganese ore (CNMO) as an effective catalyst to activate PMS for the removal of Acid Orange 7 (AO7), a harmful azo dye. CNMO exhibited a more effective activation ability than either the pure component substances alone or natural manganese ore (NMO), owing to its increased charge transfer, pore size and acidic sites. The activation mechanism of PMS was elucidated, and the degradation of AO7 was noted to have been caused by singlet oxygen (1O2), and increased electron transfer. Moreover, the outstanding degradation of AO7 in actual water indicated that the CNMO/PMS system was highly resistant to surrounding organic and inorganic compounds, and the CNMO exhibited extraordinarily high stability and recyclability. Thus, this study provides not only a new choice of PMS activator that offers low cost, and excellent and stable performance, but also a novel direction for the efficient utilization of low-grade manganese ore.

Engineering single-atom Fe-Pyridine N4 sites to boost peroxymonosulfate activation for antibiotic degradation in a wide pH range.

Single-atom Fe catalysts have shown great potential for Fenton-like technology in organic pollutant decomposition. However, the underlying reaction pathway and the identification of Fe active sites capable of activating peroxymonosulfate (PMS) across a wide pH range remain unknown. We presented a novel strategy for deciphering the production of singlet oxygen (1O2) by regulating the Fe active sites in this study. Fe single atoms loaded on nitrogen-doped porous carbon (FeSA-CN) catalysts were synthesized using a cage encapsulation method and compared to Fe-nanoparticle-loaded catalysts. It was discovered that FeSA-CN catalysts served as efficient PMS activators for pollutant decomposition over a wide pH range. Several analytical measurements and density functional theory calculations revealed that the pyridinic N-ligated Fe single atom (Fe-pyridine N4) was involved in the production of 1O2 by the binding of two PMS ions, resulting in an excellent catalytic performance for PMS adsorption/activation. This work has the potential to not only improve the understanding of nonradical reaction pathway but to also provide a generalizable method for producing highly stable PMS activators with high activity for practical wastewater treatment.

Preparation of VOC low-temperature oxidation catalysts with copper and iron binary metal oxides via hydrotalcite-like precursors.

Catalysts are the key to catalytic combustion which is known as an effective method for VOC treatment of industrial waste gas. However, in a typical catalyst, the efficiency of non-noble catalysts, with well economic, is generally poor at catalytic oxidation of VOC from industrial waste gas. In this work, a non-noble catalyst CuFe-4.5 from Cu-Fe elements combined with the properties of hydrotalcite to successfully be prepared. The difference between hydrotalcite as a precursor catalyst and the traditional method was systematically investigated by XRD, FT-IR, SEM, TG, N2 adsorption-desorption isotherms, H2-TPR, O2-TPD, and XPS. By forming the hydrotalcite structure, the structural properties of the derivative oxide catalyst can be optimized and the interaction between Cu and Fe in the system can be strengthened. It is more prone to electrons cycle, has more chemically adsorbed oxygen, facilitates catalyst surface activation and shows better efficiency. The catalyst with high activity for VOC in flue gas at low temperature, with 90% conversion at 236 °C, which is about 60 °C lower than commercial catalysts such as EnviCat® from Clariant, Germany, and also has some advantages over current studies. Our study provides a new perspective on the design of efficient VOC catalysts.

Composition Engineering of Amorphous Nickel Boride Nanoarchitectures Enabling Highly Efficient Electrosynthesis of Hydrogen Peroxide.

Developing advanced electrocatalysts with exceptional two electron (2e- ) selectivity, activity, and stability is crucial for driving the oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2 O2 ). Herein, a composition engineering strategy is proposed to flexibly regulate the intrinsic activity of amorphous nickel boride nanoarchitectures for efficient 2e- ORR by oriented reduction of Ni2+ with different amounts of BH4 - . Among borides, the amorphous NiB2 delivers the 2e- selectivity close to 99% at 0.4 V and over 93% in a wide potential range, together with a negligible activity decay under prolonged time. Notably, an ultrahigh H2 O2 production rate of 4.753 mol gcat -1 h-1 is achieved upon assembling NiB2 in the practical gas diffusion electrode. The combination of X-ray absorption and in situ Raman spectroscopy, as well as transient photovoltage measurements with density functional theory, unequivocally reveal that the atomic ratio between Ni and B induces the local electronic structure diversity, allowing optimization of the adsorption energy of Ni toward *OOH and reducing of the interfacial charge-transfer kinetics to preserve the OO bond.