Search

High substrate conversion and special hydrogenation regioselectivity of α, β-unsaturated carbonyl compounds were achieved through rigid confined space in frustrated Lewis pair/MOF catalyst. [Display omitted] • A novel catalyst was constructed by frustrated Lewis pair immobilizing in MOF. • It showed excellent regioselectivity for α,β-unsaturated carbonyl reduction. • The steric hindrance and reaction mechanism were illuminated by the DFT method. The regioselective hydrogenation of α, β-unsaturated carbonyl compounds is an extremely important transformation. However, its development is hampered by a lack of precise and efficient catalysts. In this work, triggered by the steric hindrance and confinement capacity of the catalyst, we designed a novel catalyst FLP/MIL-101(Cr), with the bulky frustrated Lewis pair (FLP) of PPh 3 and B(C 6 F 5) 3 immobilized in NH 2 -MIL-101(Cr). In the well-tailored FLP/MIL-101(Cr), the promoted selective reduction behaviors were realized, with cinnamyl alcohol selectivity up to 99 % and the complete substrate conversion in cinnamyl aldehyde reduction. Experimental characterizations and theoretical calculations indicated that the C N bond and π-π stacking interaction between FLP and the organic ligand of MIL-101(Cr) implemented and reinforced a rigid structure. Compared with homogeneous FLP, the special nano-space in FLP/MIL-101(Cr) catalyst benefits the selective reduction behavior towards the unsaturated bond with the smaller steric hindrance in α,β-unsaturated carbonyl compounds. As expected, FLP/MIL-101(Cr) showed good stabilities of skeleton structure and catalytic performance. This contribution provides an ingenious strategy to design FLP heterogeneous catalysts and represents its utilization possibility in selective reduction. [ABSTRACT FROM AUTHOR]

Electrocatalytic synthesis of aldehydes from alcohols exhibits unique superiorities as a promising technology, in which cascade reactions are involved. However, the cascade reactions are severely limited by the low selectivity resulting from the peroxidation of aldehydes in a traditional liquid‐solid system. Herein, we report a novel liquid‐liquid‐solid system to regulate the selectivity of benzyl alcohol electrooxidation. The selectivity of benzaldehyde increases 200‐fold from 0.4 % to 80.4 % compared with the liquid‐solid system at a high current density of 136 mA cm−2, which is the highest one up to date. In the tri‐phase system, the benzaldehyde peroxidation is suppressed efficiently, with the conversion of benzaldehyde being decreased from 87.6 % to 3.8 %. The as‐produced benzaldehyde can be in situ extracted to toluene phase and separated from the electrolyte to get purified benzaldehyde. This strategy provides an efficient way to efficiently enhance the selectivity of electrocatalytic cascade reactions. [ABSTRACT FROM AUTHOR]

Electrocatalytic synthesis of aldehydes from alcohols exhibits unique superiorities as a promising technology, in which cascade reactions are involved. However, the cascade reactions are severely limited by the low selectivity resulting from the peroxidation of aldehydes in a traditional liquid‐solid system. Herein, we report a novel liquid‐liquid‐solid system to regulate the selectivity of benzyl alcohol electrooxidation. The selectivity of benzaldehyde increases 200‐fold from 0.4 % to 80.4 % compared with the liquid‐solid system at a high current density of 136 mA cm−2, which is the highest one up to date. In the tri‐phase system, the benzaldehyde peroxidation is suppressed efficiently, with the conversion of benzaldehyde being decreased from 87.6 % to 3.8 %. The as‐produced benzaldehyde can be in situ extracted to toluene phase and separated from the electrolyte to get purified benzaldehyde. This strategy provides an efficient way to efficiently enhance the selectivity of electrocatalytic cascade reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The second coordination sphere of Fe site modulates its electrocatalytic activity. • A constant-potential/ hybrid-solvent model simulates electrochemical environments. • The electrode potential for ammonia production on the FeN 4 catalyst is the lowest. The first and second coordination spheres in the coordination microenvironment may regulate the electronic structure of single-metal atoms supported on carbon matrix, which in turn modulates the catalyst's catalytic activity. Simulating the kinetic process of electrocatalytic nitric oxide reduction reaction (NORR) by the theoretical modeling of electrochemical microenvironments helps understand the theoretical structure–activity relationship and guides a more rational design of electrocatalysts. In this study, density functional theory calculations combined with a constant-potential/hybrid-solvent model and microkinetic modeling are employed to study NORR mechanism on the carbon-based FeN 4 , FeN 4 -O and FeN 4 -B catalysts with different electronegativity atoms in the second coordination spheres under −1.00 ∼ 0.40 V vs. RHE. The free energy changes of all elementary reactions for NORR on the catalysts reveal that the optimal pathways for NORR on FeN 4 produce both ammonia and hydroxylamine, proceeding through the reaction intermediates *NHOH. Within −1.00 ∼ -0.37 V vs. RHE, the kinetic barriers of the rate-determining steps for NORR increase sequentially on FeN 4 , FeN 4 -O, and FeN 4 -B, corresponding to the sequentially decreasing reaction rate constants. At −6.00 mA∙cm−2, the electrode potential for ammonia production on FeN 4 catalyst is the lowest among the catalysts at −0.70 V vs. RHE, indicating it has higher electrocatalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient Co 3 O 4 catalyst is engineered by Mg doping and partial de -doping. • The obtained catalyst shows multiple surface and structure defects. • The defective Co 3 O 4 could lower the HCHO activation energy barrier. • Excellent HCHO oxidation activity is achieved over the defective Co 3 O 4. The pursuit of high-performance non-precious metal catalysts for Volatile Organic Compounds (VOCs) abatement is paramount in meeting stringent environmental regulations. In this study, we present a groundbreaking approach by crafting a highly defective Co 3 O 4 catalyst through a strategic process involving Mg doping and subsequent partial de- doping. The catalyst exhibited an exceptional activity in the oxidation of formaldehyde (HCHO), achieving a remarkable conversion rate of 2.92 μmol·m−2·h−1, which is 3.1 times that of the pristine Co 3 O 4 at 100 °C and an HCHO space velocity of 75,000 mL·g−1·h−1. Our methodology involves a dual-action process of doping and de- doping, orchestrating the introduction of significant structural and surface defects. These include surface cracks, lattice distortions, cationic vacancies, oxygen vacancies, lower metal coordination, and more. This orchestrated creation of defects serves to amplify the generation of active oxygen sites, thereby enhancing the intrinsic oxidative ability of the catalyst. The net result is a lowered activation energy barrier for HCHO, further contributing to the catalyst performance enhancement. This study not only establishes a new benchmark for Co 3 O 4 catalysis but also provides insightful paradigms for the role of defects engineering in promoting non-noble metal-catalyzed volatile organic compounds oxidation. [ABSTRACT FROM AUTHOR]

Carbon materials have rapidly grown as highly promising candidates to replace noble metal catalysts in energy storage/conversion technologies. In this work, a strategy of hydrogen‐bonding triggered assembly to configure hollow carbon nanosheets by applying Silicalite‐1 as a substrate in the aqueous solution of dopamine is reported. Remarkably, the combined density functional theory modelling and experimental verification present a molecule/nano‐scale insight into the nature of the bonding behavior during the fabrication process. It is demonstrated that the SiOH on the surface of Silicalite‐1 acts as an anchor and that it is energetically favorable to pre‐adsorb the building blocks of polydopamine by hydrogen‐bonding, which triggers the subsequent assembly. As an example, the as‐prepared hollow carbon nanosheets with unique structure can efficiently catalyze tri‐iodide reduction and a power conversion efficiency up to 8.58%. [ABSTRACT FROM AUTHOR]

Four open-framework Ag–Sn–S compounds K2Ag2Sn2S6 (1); K2Ag2SnS4 (2); Rb2Ag2SnS4 (3); and Cs2Ag2SnS4 (4) have been synthesized using a solvothermal method. Compound 1 possesses a unique three-dimensional (3D) structure in which Ag+ ions are two-coordinated. Compounds 2–4 have the same layered structure in which Ag+ ions are tetrahedrally coordinated. Photocatalytic degradation properties of methylene blue have been investigated and compound 1 displays excellent photodegradation activities. The photoelectric response properties, optical properties, and theoretical calculations of these compounds have also been studied. [ABSTRACT FROM AUTHOR]

Integration of more thermodynamically favorable valorization of biomass (e.g., glycerol), compared to sluggish oxygen evolution, with H2 production is of great significance for energy‐saving electrosynthesis of value‐added chemicals. However, its widespread deployment has been challenged by costly electrocatalysts and large overpotential reaching an industrial‐relevant current density (≥400 mA cm−2). Herein, carbon shell‐encapsulated manganese‐doped cobalt nitride nanoarrays immobilizing on nickel foam, denoted Mn‐CoN@C/NF, are crafted via hydrothermal method and ammoniation. As a bifunctional electrocatalyst, the Mn‐CoN@C/NF manifests extraordinary activity for glycerol oxidation reaction (GOR) with an ultralow potential of 1.37 V (versus RHE) at 400 mA cm−2, in conjunction with H2 evolution reaction (HER) with a low overpotential of 31 mV at 10 mA cm−2. A record high Faradaic efficiency (97.7%) for formate production of GOR is delivered at 1.35 V (vs RHE). Impressively, a two‐electrode electrolyzer capitalizing on the Mn‐CoN@C/NF as catalysts reaches 800 mA cm−2 at 1.83 V, delivering an electricity‐saving efficiency of 15.0% compared to pure water splitting. DFT calculations substantiate that Mn species within Mn‐CoN not only optimize hydrogen adsorption kinetics for HER, but also elevate Co3+ active sites' density for GOR. This work offers an energy‐saving and efficient electrosynthesis avenue for coproduction of valuable chemicals. [ABSTRACT FROM AUTHOR]

The low‐voltage charging capacity and rate performance are two crucial but mutually restricted properties of K‐ion batteries. Herein, a sulfonamide and amide linkages‐triggered N doping high‐temperature removal strategy is proposed to obtain porous carbon with rich carbon vacancies, high sp2 hybridized C content (65.3%), and large interlayer spacing using coal tar pitch as carbon precursor. Carbon vacancies and sp2 hybridized C are proved to be not only active sites for low‐voltage potassium storage but also conducive to the fast transfer of ions and electrons, endowing reversible and fast potassium storage at low voltage. Moreover, abundant carbon vacancies and large carbon interlayer spacing alleviate volume variation, improving the cycling stability for 8500 cycles (about 3700 h). This work sheds new light on the design of low‐voltage, durable, and fast potassium storage carbon anodes, and promotes the development of practical carbon anodes for high energy density K‐ion batteries in the future. [ABSTRACT FROM AUTHOR]

The theoretical investigation of electronically excited stated intermolecular hydrogen bonding dynamics of the 2D luminescent polypyrene covalent organic framework and methanol molecule (PPy-COF-MeOH) was performed using the density functional theory (DFT) and time-dependent (TD-DFT) method. The strengthening of Hydrogen bonds C-H---O-H and B-O---H-O upon photoexcitation was confirmed via comparison of geometric structures, electronic transition energies, 1H-NMR, binding energies, UV-Vis and infrared spectra in S0 and S1 states. Frontier molecular orbitals (MOs) analysis, electronic configuration, Mulliken charge analysis; and the charge density variation in hydrogen bonding proximity demonstrated that the strengthened hydrogen bonds facilitate the nonradiative path which may consequently proceed the luminescence quenching. Hence, the molecular material property prediction package (MOMAP) programme verified the fluorescence quenching because PPy-COF-MeOH complex showed a lower fluorescent rate constant compared to isolated PPy-COF fragment. The S1-T1 energy gap analysis also revealed the possibility of the Intersystem crossing (ISC). Above results significantly highlighted the role of the hydrogen bonding dynamics on luminescence property of the PPy-COF. [ABSTRACT FROM AUTHOR]

Abstract Triphenylamine-based cyclometalated platinum(II) (TCP) emits phosphorescence at room temperature. The phosphorescence was quenched by oxygen molecule, which means that TCP is a good candidate for oxygen molecule recognition and measurement. By the way of quantum chemical calculation, we proposed the quenching mechanism to elucidate the nature of oxygen sensing, which was different from the traditional dynamic collision mechanism. The luminescence mechanism of TCP involves phosphorescent emission, and the TCP-O 2 complex fluorescent emission. By utilizing the density functional theory (DFT) method, we calculated the electron configurations and the frontier molecular orbitals of TCP and the TCP-O 2 complex. Furthermore, applying the time-dependent density functional theory (TDDFT) method, we calculated the geometric optimization and the excitation energies of TCP and the TCP-O 2 complex in the excited state. The results illustrate that the luminescence of TCP stems from localized excitation, while that of the TCP-O 2 complex stems from delocalized excitation. Moreover, we also calculated the radiative and non-radiative rate constants of TCP and the TCP-O 2 complex and clarified the photophysical processes of them. For TCP, first the electron arrived at the T 1 state via intersystem crossing from the initial S 1 state and finally back to the S 0 state via emitting phosphorescence. For the TCP-O 2 complex, with no spin flip, the electron jumped directly from the T 1 to T 0 state via internal conversion. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract Photodegradation is one of the major degradation paths for antibiotics as aquatic micropollutants in surface water. The photodegradation involves a number of complicated photophysical and photochemical processes. Exploration for the rate-limiting step among these processes can be essential for the elimination of antibiotics. In this work norfloxacin was selected as a target compound. The rate constants of photophysical transitions and their competitions were discussed under the framework of Fermi Golden rule and time-depended perturbation theory. Using density functional theory, the reaction paths in triplet state were searched. The competitions among the photophysical transitions and photochemical reaction paths indicate the intersystem crossing (ISC) from the S 1 state to T 1 state is the rate-limiting step in the aquatic photodegradation of norfloxacin. Ca2+ ion significantly accelerates this bottleneck by coordinating with the carbonyl and carboxyl groups of norfloxacin. The coordination creates more ISC paths to triplet states and increases the spin-orbit coupling, Huang-Rhys factors, and the vibrational coupling of the ISCs. Graphical abstract Image 1 Highlights • Comprehensively studied photophysical and photochemical processes of Norfloxacin. • Identified intersystem crossing as the rate-limiting step of photodegradation. • Enhanced photophysical characteristics by Ca2+ ion. • Theoretical exploration under the framework of Fermi Golden rule. [ABSTRACT FROM AUTHOR]

The investigation of intermolecular hydrogen bonding between the luminescent polypyrene covalent organic framework and formaldehyde (PPy-COF-HCHO) was carried out with the density functional theory and time-dependent density functional theory. The strengthening of the photoexcited hydrogen bond C = O—-H-C was verified via geometric structures, electronic transition energies, binding energies, UV-Vis and infrared spectra comparison in both ground state and excited state of the PPy-COF's truncated representative fragment. From the frontier molecular orbitals examination, natural population analysis, and plotted electron density difference map demonstrated that the strengthened hydrogen bond facilitated the rearrangement of electron density between H-donor and H-acceptor moieties which should account for charge transfer and ultimate fluorescence quenching. Interestingly, the energy gap between excited state and triplet state of the hydrogen-bonded complex showed the possibility of the intersystem crossing. The MOMAP programme further confirmed the quenching process because there was a lower fluorescent rate constant for the donor-acceptor PPy-COF-HCHO complex compared to free PPy-COF fragment. Results above significantly highlighted the high sensitivity of the PPy-COF towards organic analyte, i.e. the formaldehyde and can be employed as a sensor. [ABSTRACT FROM AUTHOR]

By means of a H218O labeling experiment in combination with mass spectrometry tracking, we studied GO photoreduction. Observation of 18O labeled O2 provides direct evidence to confirm that water oxidation occurs during GO photoreduction. In combination with DFT calculations, we propose a mechanism for O2 and CO2 evolution in the photoreduction of GO. [ABSTRACT FROM AUTHOR]

In terms of ‘green chemistry’ and ‘atom economy’, the cycloaddition of CO 2 to yield cyclic carbonate without any additive is an eco-friendly way to utilize CO 2 . Unfortunately, the low CO 2 capture quantity of common catalysts limited its catalytic efficiency. Herein, a novel acid-base bifunctional catalyst was successfully prepared by immobilizing ionic liquid on MIL-101-NH 2 (IL/MIL-101-NH 2 ) and tested for propylene carbonate (PC) rapid and facile synthesis from CO 2 and propylene oxide (PO). The synergetic interaction between Lewis base with strong CO 2 chemical capture capacity and Brønsted acid with strong hydrogen bond donor leads to the high catalytic efficiency of IL/MIL-101-NH 2 for carbonate synthesis from CO 2 and PO without any additive. The immobilization mode between MIL-101-NH 2 and IL is energetically supported by the density functional theory (DFT) calculations. This design idea of specific catalyst and the acid-base synergetic strategy provides new insights into the design of powerful catalyst systems for the CO 2 conversion. [ABSTRACT FROM AUTHOR]

This article presents a recognition mechanism for nitro-explosives by the luminescent metal-organic framework 1 (LMOF-1) with the aid of density functional theory (DFT) and time-dependent density functional theory (TDDFT). The behavior of hydrogen bonding between the LMOF-1 and nitro-explosives in the S 1 state is closely associated with the fluorescence properties of the LMOF-1. In our research, we calculated the geometric configuration, 1 H NMR and IR spectra of the Complex 2 formed by LMOF-1 and nitrobenzene in the S 0 and S 1 states. The results showed that the hydrogen bond in the S 1 state was increased, which was unfavorable for the luminescence of LMOF-1. Furthermore, the fluorescence rate of LMOF-1 decreased after encapsulating nitrobenzene into it. These calculated results collectively suggest that LMOF-1 is a potential fluorescence sensor for the detection of nitro-explosives. This research was aiming to provide a better understanding of the recognition mechanism by LMOFs for nitro-explosives. [ABSTRACT FROM AUTHOR]

For organic pollutants, photodegradation, as a major abiotic elimination process and of great importance to the environmental fate and risk, involves rather complicated physical and chemical processes of excited molecules. Herein, we systematically studied the photophysical and photochemical processes of a widely used antibiotic, namely sulfapyridine. By means of density functional theory (DFT) computations, we examined the rate constants and the competition of both photophysical and photochemical processes, elucidated the photochemical reaction mechanism, calculated reaction quantum yield ( Φ ) based on both photophysical and photochemical processes, and subsequently estimated the photodegradation rate constant. We further conducted photolysis experiments to measure the photodegradation rate constant of sulfapyridine. Our computations showed that sulfapyridine at the lowest excited singlet state (S 1 ) mainly undergoes internal conversion to its ground state, and is difficult to transfer to the lowest excited triplet states (T 1 ) via intersystem crossing (ISC) and emit fluorescence. In T 1 state, compared with phosphorescence emission and ISC, chemical reaction is much easier to initiate. Encouragingly, the theoretically predicted photodegradation rate constant is close to the experimentally observed value, indicating that quantum chemistry computation is powerful enough to study photodegradation involving ultra-fast photophysical and photochemical processes. [ABSTRACT FROM AUTHOR]

Methane dry reforming (DRM) is a promising approach to convert two greenhouse gases, CO 2 and CH 4 , into industrial value syngas (H 2 and CO). However, traditional photocatalytic and thermal catalytic DRM face problems of low yield and high energy consumption. Recently, new photo-thermal synergistic catalytic DRM methods have been developed, which greatly enhance catalytic activity and stability while reducing energy consumption. In this review, the photo-thermal synergistic catalytic DRM process is divided into two groups based on the role played by light and heat energy: thermal assisted photocatalytic DRM and light-driven thermocatalytic DRM. Then, the catalytic mechanisms and catalyst development of two types of photo-thermal synergistic catalytic DRM process are elaborated, aiming to improve catalytic activity, stability, and selectivity from the perspectives of catalytic methods and catalyst design. Finally, the future challenges and opportunities for the development of photo-thermal synergistic catalytic DRM are proposed. • A detailed overview is provided on the synergistic mechanism of light and heat for photo-thermal synergistic catalytic DRM. • A summary of the latest research results on catalysts and catalytic mechanisms are provided. • The future challenges and opportunities for the development of photo-thermal synergistic catalytic DRM are proposed. [ABSTRACT FROM AUTHOR]

• P or O atoms doping MoS 3 catalysts could effectively modulate the catalyst's electronic structure of the Mo1 active site. • MoS 3 , P atom doping, and a tiny amount of O atom doping catalysts activate N 2 through the π *-acceptation effect, while the catalysts with more O atoms content activate N 2 through the σ-donation effect. • The MoS 8/3 O 1/3 catalyst exhibits good catalytic activity for eNRR under the constant-potential method. Heteroatom doping is an effective strategy to enhance the catalytic activity of catalysts. In this study, we propose a series of heteroatom doping (P, O) MoS 3 catalysts to investigate the effect of heteroatoms on the catalytic activity of these catalysts for electrocatalytic nitrogen reduction reaction (eNRR). In P doping catalysts, the electron-donating ability of the Mo1 active site is improved by raising the P atom content, and N 2 is activated by the π *-acceptation effect. In O doping catalysts, the electron-accepting ability of the Mo1 active site is improved by raising the O atom content, meanwhile, the N 2 activation process transforms from the π *-acceptation effect to the σ-donation effect. The reaction mechanism of the catalysts can be accurately depicted under the constant-potential method, the calculated results elucidate that the MoS 8/3 O 1/3 catalyst with a tiny amount of O atom exhibits good catalytic activity for eNRR with the limiting potential of -0.43 V vs. RHE. Additionally, the E ads (*N 2) and E ads (*NNH) can be served as the descriptors to understand the origins of catalytic activity for the catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, a facile one-step approach is reported for using ZIF-67 as a sacrificial template in the synthesis of a counter electrode (CE) catalyst for dye-sensitized solar cells (DSCs). Porous nanocomposites of Co, CoO and N-doped graphitic carbon were synthesized by controlling the carbonization temperature of the templates in a N 2 atmosphere. The characterization of the structure of the products indicated that cobalt nanoparticles were embedded in an N-doped graphitic carbon matrix, (a core-shell structure termed Co@NGC) while cobalt and cobalt oxide nanoparticles were exposed on the external surface of the carbon (termed Co/CoO). In particular, the chemical stability of the nanostructure of the Co@NGC was superior to Co/CoO with respect to etching by strong acids such as hydrochloric acid (HCl, 0.1 M). The DSC performance of ZIF-67-850 (pyrolyzed at 850 °C) employed as a CE resulted in a photoelectric conversion efficiency (PCE) of 7.92%, which was close to a Pt CE (8.18%) in the liquid I 3 − /I − redox couple electrolyte. The excellent performance of ZIF-67-850 can be attributed to the synergetic effects between the Co and CoO coupled with the nitrogen doped graphitic carbon. The cost-effective porous Co/CoO and Co@NGC nanocomposites exhibit great potential for application as high performance CE in solar cells. [ABSTRACT FROM AUTHOR]

This paper investigates the luminescent properties of luminescent metal-organic framework (LMOF) [Zn 2 (oba) 2 (bpy)], and its selectivity for the detection of nitro-explosives via fluorescence quenching, using the density functional and time-dependent density functional theories. The luminescent mechanism of the LMOF follows the electron transfer from ligand to ZnO quantum dot. The hydrogen bondings formed between LMOF and electron-withdrawing nitro-explosives as well as electron-donating aromatic compounds have different influences on the luminescent mechanism of the LMOF. The hydrogen bonding in the excited state was investigated to display the relationship between hydrogen bonding and fluorescence. [ABSTRACT FROM AUTHOR]

Environmental problems due to the discharge of gases, including NO and CO 2 , in addition, diseases caused by improper concentration of NO and CO 2 in vivo must be resolved. In this study, Grand canonical Monte Carlo (GCMC) simulations are combined with density functional theory (DFT) to calculate the adsorption of NO and CO 2 from a dual-component mixture to the Cu-BTC metal organic framework. The results show that the adsorption isotherms for various molar ratios of the gaseous mixture followed a Langmuir distribution. At higher pressures more CO 2 than NO was adsorbed by Cu-BTC, with NO showing a tendency to desorb. However, better results for adsorption of NO were observed at lower pressures. For the different pressure and molar ratios of the gaseous mixture examined, more CO 2 than NO was always adsorbed. Compared with three-way catalysts, Cu-BTC offers benefits to adsorption of CO 2 and NO from gaseous mixtures without increased durability problems. [ABSTRACT FROM AUTHOR]

Sulfadiazine (SDZ) mainly proceeds triplet-sensitized photolysis with dissolved organic matter (DOM) in the aquatic environment. However, the mechanisms underlying the triplet-sensitized photolysis of SDZ with DOM have not been fully worked out. In this study, we investigated the mechanisms of triplet-sensitized photolysis of SDZ 0 (neutral form) and SDZ − (anionic form) with four DOM analogues, i.e., fluorenone (FL), thioxanthone (TX), 2-acetonaphthone (2-AN), and 4-benzoylbenzoic acid (CBBP), and three metal ions (i.e., Mg 2+ , Ca 2+ , and Zn 2+ ) effects using quantum chemical calculations. Results indicated that the triplet-sensitized photolysis mechanism of SDZ 0 with FL, TX, and 2-AN was hydrogen transfer, and with CBBP was electron transfer along with proton transfer (for complex SDZ 0 -CBBP2) and hydrogen transfer (for complex SDZ 0 -CBBP1). The triplet-sensitized photolysis mechanisms of SDZ − with FL, TX, and CBBP was electron transfer along with proton transfer, and with 2-AN was hydrogen transfer. The triplet-sensitized photolysis product of both SDZ 0 and SDZ − was a sulfur dioxide extrusion product (4-(2-iminopyrimidine-1(2H)-yl)aniline), but the formation routs of the products for SDZ 0 and SDZ − were different. In addition, effects of the metal ions on the triplet-sensitized photolysis of SDZ 0 and SDZ − were different. The metal ions promoted the triplet-sensitized photolysis of SDZ 0 , but inhibited the triplet-sensitized photolysis of SDZ − . [ABSTRACT FROM AUTHOR]

The influence of CH 3 OH solvent on the luminescent properties of the [Zn(sfdb)(bpy)(H 2 O)] n · 0.5 n CH 3 OH (sfdb = 4,4-sulfonyldibenzoic acid, bpy = 2,2-bipyridine) metal–organic framework (MOF) was investigated by considering the hydrogen bond between CH 3 OH and [Zn(sfdb)(bpy)(H 2 O)] n in an electronically excited state using density functional theory and time-dependent density functional theory methods. The calculated geometry, infrared spectrum, and UV–vis spectrum in the ground state are consistent with the experimental results. The frontier molecular orbitals and electronic configuration indicated that the origin of the luminescence is ligand-to-ligand charge transfer rather than ligand-to-metal charge transfer, as has been previously proposed. We found that the O3⋯H11 hydrogen bond is weaker in the excited state than in the ground state, and the weaker hydrogen bond in the electronically excited state should enhance the luminescence. The results show that the CH 3 OH solvent changes the luminescence properties of [Zn(sfdb)(bpy)(H 2 O)] n , which provides potential opportunities for the design of diverse luminescent MOFs. [ABSTRACT FROM AUTHOR]

The catalytic performance of carbon nanotubes has still been hindered by the intrinsic and limited in‐plane electrocatalytic active sites, with a focus on improving their catalytic activity by covalent modifications, which require the relatively high energy input to dissociate the in‐plane atoms and create the active sites. Herein, an effective route is developed to modulate the in‐plane defective density and electronic structure of multi‐walled carbon nanotubes (MWCNTs) by ultra‐small‐sized g‐C3N4 quantum dots (CNQDs) with abundant nitrogen species via π–π stacking. The non‐covalent bonded CNQDs on MWCNTs endow them with abundant catalytic active sites on the basal plane, still inheriting the intrinsic and fast electron‐transfer characteristics of MWCNTs. The optimized CNQDs/MWCNTs‐4 heterogeneous catalyst exhibits an optimal photoelectric conversion efficiency of up to 8.30% in probing reaction for triiodide reduction, outperforming the Pt reference (7.86%). The thermodynamic calculations further reveal that the CNQDs integrated on MWCNTs are capable of reducing the reaction energy barrier (ΔG) of the rate‐determining step from I2 to I− and adsorption state I*. The present study provides an efficient and non‐covalent strategy to construct excellent carbon‐based catalysts with abundant active sites, which is also enlightening for the preparation and application of other carbon‐based catalysts. [ABSTRACT FROM AUTHOR]

Liquids with no ions! Raman analysis and quantum calculations suggest that electrically neutral molecular species predominantly exist in an N‐methylimidazole and acetic acid equimolar mixture, and that ionic species are rather minor. Nevertheless, the mixture has significant ionic conductivity, and shows “good ionic” or “superionic” behavior (see figure). It may be suitable to call such liquids “pseudo‐ionic liquids” rather than “ionic liquids”. [ABSTRACT FROM AUTHOR]

• Six thioarsenates and thioantimonates with different valences of As/Sb were synthesized by adjusting the temperature. • Cs 2 Ag 6 As 2 S 7 (5) exhibits the highest Ag/As ratio among the known quaternary sulfides. • Compounds 4 and 5 exhibit excellent photoelectric responsive properties. [Display omitted] Six thioarsenates and thioantimonates with different valences of As/Sb were synthesized solvothermally by adjusting the synthetic temperature. Rb 2 AgAsS 4 (1), Cs 2 AgAsS 4 (2), Cs 2 AgSbS 4 (3) in which As and Sb are pentavalent were obtained in the lower temperature system and RbAg 2 AsS 3 (4), Cs 2 Ag 6 As 2 S 7 (5), and CsAg 2 SbS 3 (6) in which As and Sb are trivalent were synthesized under a higher temperature. Compounds 1 – 3 possess the same one-dimensional (1D) chain structure and 4 – 6 are two-dimensional (2D) layered compounds. In particular, 5 exhibits the highest Ag/As ratio (3.0) among the known quaternary sulfides, and rare octahedral coordinated S2- ions that coordinate with six Ag+ ions exist in the structure of it. Their optical properties, photoelectric response properties, and theoretical calculations have also been studied. [ABSTRACT FROM AUTHOR]

Nanoplate‐shaped Ni(OH)2 with numerous exposed active sites hold much promise for high‐performance energy storage devices. However, restricted by the wide band gap, which leads to a low concentration of charge carrier, the energy barrier of electron mobility in lattice plane is high, further inhibiting the electron transfer and their practical application. Here, several unique processable nickel‐based hydroxide films are constructed via the cation‐inserted strategy to probe the intrinsic relationship between component and electronic micro‐structure. Benefiting from the component‐driven effects, the concentration of charge carrier at the lattice plane can be accumulated after injecting heterogeneous cations, and the fastened dynamics process can be realized and confirmed by multiple real‐time operando techniques. Meanwhile, the more well‐matched Co core rather than Mn core in Ni(OH)2 is also certified. Finally, the CoNi(OH)2 electrode achieves 623 C g–1 @1 A g–1 without any conductivity additives and binders, which is nearly threefold that of pristine Ni(OH)2. This work clarifies the critical role of inserted cations, and corresponding electron and electrolyte ion transfer across the matrix, thus enabling a better guideline for Ni(OH)2‐based energy storage/conversion systems. [ABSTRACT FROM AUTHOR]

The hydrogen bonding between ammonia (NH 3) and a two-dimensional material 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP)-4,4′-diphenyl-butadiynebis (boronic acid) (DPB) covalent organic framework (HHTP-DPB COF) in its electronically excited state was investigated using density functional theory and time-dependent density functional theory. The formation of the hydrogen bonding changed the luminescence mechanism of the material, which was confirmed by analysis of the frontier molecular orbitals and the corresponding electronic configurations. The comparison of the properties of hydrogen bonds in the ground state (S 0) and excited state (S 1) revealed that in the S 1 state the hydrogen bonds were strengthened, which was adverse to the radiation transition process, and resulting in the weakening of the fluorescence intensity. After the introduction of NH 3 , the fluorescence rate constant of the COF was decreased and the internal conversion rate constant was increased. Therefore, these findings indicated that HHTP-DPB COF has great application prospects for detecting the indoor air pollutant NH 3. [ABSTRACT FROM AUTHOR]

Two compounds Ba 2 Cu 2 Cd 2 S 5 (1) and Ba 3 Cu 4 Hg 4 S 9 (2) have been successfully synthesized under mild solvothermal conditions by using thiophenol as a mineralizer. Compound 1 features an anionic [Cu 2 Cd 2 S 5 ] n 4n− layer constructed by trigonal planar CuS 3 and tetrahedral CdS 4. Compound 2 possesses a unique [Cu 4 Hg 4 S 9 ] n 6n− layer composed of trigonal planar CuS 3 and linear HgS 2. Rare linear-coordinated sulfur and square-planar tetra-coordinated sulfur exist in the structures of 1 and 2 , respectively. In addition, the thermal stabilities, optical properties, photoelectric responses, as well as the band gap calculations of the two compounds were also studied in detail. Image 1 • Two layered sulfides Ba 2 Cu 2 Cd 2 S 5 (1) and Ba 3 Cu 4 Hg 4 S 9 (2) were synthesized by solvothermal method. • Thiophenol (PhSH) was used as an effective mineralizer in the mild method. • Unusual linear-coordinated and square-planar tetra-coordinated sulfur exist in compounds 1 and 2 , respectively. • Ba 2 Cu 2 Cd 2 S 5 (1) exhibits excellent photocurrent responsive property. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 reacted with alcohols to first form monoalkyl carbonates. • Monoalkyl carbonates reacted with alcohols to generate dialkyl carbonates. • The reaction type of rate-determining step conformed to esterification reaction. • The formation of monoalkyl carbonates limited the conversion of whole reaction. • The temperature should from 237 to 252 K and the CO 2 pressure higher than 1 MPa. The direct conversion of CO 2 by alcohols has attracted wide attention as it offers a new green method of capturing CO 2 with high selectivity. However, its biggest drawback is that its yield is extremely poor. In order to understand and address this issue, it is necessary to study the kinetic and thermodynamic processes of dialkyl carbonate formation, and develop effective catalysts for the rate-determining step. Here, we applied the density function theory to determine its molecular mechanism. The results showed that CO 2 reacted with alcohols to first form monoalkyl carbonates, and then the monoalkyl carbonates further reacted with alcohols to generate dialkyl carbonates. In terms of kinetics, three alcohol molecules could directly activate CO 2 , and dialkyl carbonates formation was the rate-determining step, which conformed to the characteristics of an esterification reaction. In terms of thermodynamics, the formation of monoalkyl carbonates limited the conversion of the whole reaction. Pressuring CO 2 and lowering the temperature contributed to its conversion. However, high temperature was conducive to increase the conversion of dialkyl carbonates. Ultimately, we proposed the suitable experimental conditions in which the temperature range was from 237 to 252 K and the CO 2 pressure should be higher than 1 MPa. [ABSTRACT FROM AUTHOR]

This paper investigates the sensitivity of the luminescent thieno[2,3- b ]thiophene-based covalent organic framework (TT-COF) towards the formaldehyde using the density functional theory and time-dependent method. The hydrogen bonding dynamics is explored by comparison of geometries, electronic transition energies, binding energies, UV–vis, and infrared spectra. Frontier molecular orbitals examination, natural population analysis, and plotted electron density difference map describe the quenching process explicitly via electron density distribution. The MOMAP program illuminates the quenching owing to TT-COF-HCHO complex radiative rate constant. Furthermore, the S1-T1 energy gap describes the facilitation of the luminescence quenching through the intersystem crossing. Above all results elaborate the TT-COF's potential to detect the formaldehyde. Unlabelled Image • TD-DFT investigation for intermolecular hydrogen bonding dynamics • Excited-state hydrogen bond complex shows redshift • The fluorescence of TT-COF is quenched due to enhanced hydrogen bonding • Energy gap facilitates the intersystem crossing process [ABSTRACT FROM AUTHOR]

Developing metal‐free carbon catalysts with designable high nitrogen (N) content yet well‐organized N distribution within carbon at nanoscale is still one of the paramount challenges for electrochemical CO2 conversion. Herein, a gradient N doping enabled by the energetic microwave irradiation is realized along the radial direction of carbon nanotubes (CNTs), with an ultrahigh surface N content of 30.5 at%, beyond the upper limit of the tradition pyrolysis method. The unique time‐domain features of microwave heating presented as the sub‐minute residence time for precursors and relatively mild surface temperature on CNTs, contributing to the maximum reservation of the surface N species. The catalyst exhibits a prominent performance with great activity and selectivity for electrochemical CO2‐to‐CO conversion. Theoretical calculation confirmed the catalyst with high N‐doping level can promote the adsorption of CO2 molecule, with a low adsorption energy of −3.35 eV. This work provides a novel prototype to construct the distribution‐controlled and space‐intensive active sites over functional gradient metal‐free carbon materials. [ABSTRACT FROM AUTHOR]

It is of important theoretical significance to research the mechanism of luminescent covalent organic frameworks (LCOFs) for detecting nitro-explosives. The interaction between LCOF-BTT1 and nitrobenzene has been investigated by DFT and TDDFT methods. By studying electronic configurations and frontier molecular orbitals, the luminescence mechanism of LCOF-BTT1 has changed due to the hydrogen bonding formed between LCOF-BTT1 and nitrobenzene (Complex 1). Further study of electronic transition energies, hydrogen bond lengths, 1H NMR and IR spectra of Complex 1 reveals that hydrogen bonding is stronger in the excited state than in the ground state, indicating fluorescence quenching. Furthermore, the fluorescence rate coefficient and the internal conversion rate coefficient of Complex 1 are correspondingly decreased and increased, indicating that the increase in the strength of hydrogen bonding in the excited state is beneficial to the non-radiative transition and is not conducive to the radiation transition. • The luminescent mechanism of LCOF-BTT1 was studied by TDDFT method. • Hydrogen bonding between LCOF and nitrobenzene strengthens in the excited state. • Excited state hydrogen bonding strengthens induces fluorescence quenching. • Increased excited state hydrogen bonding strength favors non-radiative transition. [ABSTRACT FROM AUTHOR]

Supercapacitor combining advantages of conventional capacitor and battery is an outstanding energy storage device with high energy density and power density. Co 3 S 4 is an attractive material for supercapacitors due to its high theoretical capacitance. However, its low experimental capacitance limits its practical application due to sluggish ion transport kinetics and pronounced volumetric expansion during energy storage process. This study designs and configurates double-shelled hollow Ni x Co 3− x S 4 spheres via atom-level structure engineering, where Ni atoms replace Co atoms and regulate the valences of Co. Among these sulfides with different amount of Ni substitution, Ni 1.5 Co 1.5 S 4 shows the highest specific capacitance 2210 F g−1 at 0.5 A g−1, even maintains 1154 F g−1 at a high current density of 20 A g−1 and good cycle stability (87.0% retention after 3000 cycles). The excellent electrochemical properties of Ni 1.5 Co 1.5 S 4 can be attributed to the optimized amount of Ni substitution, accordingly improved conductivity and fast transportation of OH−. What's more, Ni 1.5 Co 1.5 S 4 //activated carbon (AC) asymmetric device also delivers excellent energy density (36.94 Wh kg−1 at 0.15 kW kg−1). Atomic-level structure engineering Ni substitution improves the electronic conductivity and OH− diffusion of Ni x Co 3- x S 4 , and Ni 1.5 Co 1.5 S 4 delivers the highest capacitance. Unlabelled Image • Ni-substituted cobalt sulfides are prepared via atomic-level structure engineering. • Ni 1.5 Co 1.5 S 4 delivers the highest capacitance and good cycling stability. • Ni substitution can increase the electronic conductivity and diffusion rate of OH−. • Double hollow structure could increase active sites to absorb and react with OH−. • Ni 1.5 Co 1.5 S 4 //AC achieves excellent energy density of 36.94 Wh kg−1 at 0.15 kW kg−1. [ABSTRACT FROM AUTHOR]

Luminescent covalent organic frameworks (COFs) as fluorescent sensor materials provide a distinct advantage over other materials. In this work, we investigated the hydrogen bonding between the luminescent COF Ph-An-COF and formaldehyde in its excited electronic state by using density functional theory and time-dependent density functional theory to determine whether this type of COF can be used for formaldehyde detection. Hydrogen bonding significantly changed the nature of the frontier orbital and the luminescent properties. Our study reveals that the hydrogen bonding was strengthened in the excited state and the fluorescence rate coefficient was significantly reduced, which is not favorable for the luminescence of this type of COF and would lead to a luminescence decrease or quenching phenomenon. Therefore, this type of luminescent COF can be used as a potential chemical sensor to detect formaldehyde. This work provides an insight into the design of luminescence covalent organic frameworks. [ABSTRACT FROM AUTHOR]

Direct CO2 electrolysis in seawater enables the simultaneous conversion of CO2 into CO and the chlorine ions into Cl2, further meeting downstream industry needs such as phosgene synthesis and also facilitating the net consumption of CO2. As a result, the direct implementation of CO2 electrolysis in seawater is urgently required. Herein, a CoPc molecule‐implanted graphitic carbon nitride nanosheets (CoPc/g‐C3N4) electrocatalyst is prepared via a simple mechanochemistry method. The CoPc/g‐C3N4 with a negatively charged surface and preferential adsorption capability for Na+ can achieve appreciable faradaic efficiency (FE, 89.5%) toward CO with a current density of 16.0 mA cm−2 in natural seawater and also realize long‐term operation for 25 h in simulated seawater. Process monitoring further reveals that the chlorine ions in NaCl electrolyte can modulate the reaction microenvironment around the anode, which in turn has positive effects on the CO2RR in cathode. The CO2RR overall splitting in the simulated seawater exhibits a maximum FE of 98.1% towards CO at cell voltage of 3 V. This work describes the development of a carbon‐coupled CoPc molecular catalyst that can drive the CO2 electrolysis in simulated seawater and provides a promising and energy‐saving coupled reaction system for direct coproduction of CO and Cl2. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the role of excited-state hydrogen bonding in the photocatalytic carbon dioxide reduction reaction (CO2RR) utilizing Rose Bengal as a catalyst, through a combined experimental and theoretical approach. Experiments validated the successful conversion of CO2 to CO in a homogeneous aqueous solution system under light irradiation, without additional photosensitizers or sacrificial agents. Theoretically, the DFT/TDDFT calculations modeled the catalyst-reactants as a hydrogen-bonded complex (HBC), understanding the energy, hydrogen, and electron transfer mechanisms induced by excited-state hydrogen bonding. Combining the photophysical and photochemical insights revealed the complete catalytic cycle, identifying the water oxidation process as the rate-limiting step in the entire photocatalytic CO2RR process. Experimental and computational results provide molecular-level insights into the structure–activity relationships. This work enhances comprehension of the pivotal role of excited-state hydrogen bonding and holds significant reference value for enhancing the conversion efficiency in the photocatalytic CO2RR. [ABSTRACT FROM AUTHOR]

Glycolaldehyde (HOCH2CHO, GA), the simplest molecule containing both hydroxyl and aldehyde groups, is structurally the most elementary member of monosaccharide sugars, which may provide new clues for probing the origin of life on planets like the Earth. Uncovering the existing state of GA in solution systems is an important scientific issue. Generally, methanol is used as the main mobile phase in the liquid chromatography analysis of GA, but the state of GA existing in methanol solution remains unknown, thus making it difficult to analyse GA accurately. Herein, the state and dynamic equilibrium of GA in methanol solution were systematically studied by UV-visible spectroscopy, nuclear magnetic resonance (1H-NMR) spectroscopy, liquid chromatography mass spectrometry (LC–MS) and density functional theory (DFT) calculations. The results demonstrated that the equilibrium component of GA in methanol solution is different from that in aqueous solution and that glycolaldehyde hemiacetal (GAHA) is a dominant component (>90%). Laying the foundation for experimental analysis, the transformation of different components at equilibrium was studied using DFT. The results confirm that hydrogen bonding-induced proton transfer occurs between the components at equilibrium. This work provides an important reference for the analysis of sugars and related compounds in various biochemical reactions. [ABSTRACT FROM AUTHOR]

An efficient chemical synthesis route, with an aim of reaching an ultrahigh nitrogen (N)‐doping level in carbon materials can provide a platform where the type and amount of N dopant can be tuned over a wide range. We propose a C‐S‐C linkage‐triggered confined‐pyrolysis strategy for the high‐efficiency in situ N‐doping into carbon matrix and an ultrahigh doping level up to 13.5 at %, which is close to the theoretical upper limit (15.2 at %) is realized at a high carbonization temperature of 1000 °C. The pyridinic N is dominant with a maximum percent of 48.7 %. By using I3− reduction as an example, the resultant NCM‐5 exhibits the best activity with a power conversion efficiency of 8.77 %. A pyridinic N site‐dependent activity is demonstrated in which the amount of active sites increases with the increase of pyridinic N, and the carbon atom adjacent to electron‐withdrawing pyridinic N at the armchair edge acts as the most favorable site for the adsorption of I2. [ABSTRACT FROM AUTHOR]

An efficient chemical synthesis route, with an aim of reaching an ultrahigh nitrogen (N)‐doping level in carbon materials can provide a platform where the type and amount of N dopant can be tuned over a wide range. We propose a C‐S‐C linkage‐triggered confined‐pyrolysis strategy for the high‐efficiency in situ N‐doping into carbon matrix and an ultrahigh doping level up to 13.5 at %, which is close to the theoretical upper limit (15.2 at %) is realized at a high carbonization temperature of 1000 °C. The pyridinic N is dominant with a maximum percent of 48.7 %. By using I3− reduction as an example, the resultant NCM‐5 exhibits the best activity with a power conversion efficiency of 8.77 %. A pyridinic N site‐dependent activity is demonstrated in which the amount of active sites increases with the increase of pyridinic N, and the carbon atom adjacent to electron‐withdrawing pyridinic N at the armchair edge acts as the most favorable site for the adsorption of I2. [ABSTRACT FROM AUTHOR]

Abstract To design a highly efficient electrocatalyst for cathodes to suppress the high overpotential for the oxygen reduction reaction (ORR) continually remains a prime goal of fuel cell study. Herein, the production of metal–free hollow nitrogen–doped carbon microspheres (HN–CMs) as an efficient electrode material for the supercapacitors and ORR in an alkaline media is reported. Initially, the PS@PANI core–shell microspheres were produced by coating polyaniline (PANI) layers on polyvinylpyrrolidone (PVP) functionalized polystyrene (PS) microspheres via in–situ chemical polymerization of aniline monomers in presence of ammonium persulphate (APS) as an oxidant. Finally, the core was removed by carbonizing the core–shell microspheres under the N 2 atmosphere at 500 °C for 2 h to obtain the HN–CMs as an electrocatalyst. The structure and morphologies of the microspheres were examined by SEM, TEM, XRD, FT–IR, BET, and Raman spectroscopy. The electrochemical analysis was performed by CV, GCD, and EIS. The obtained electrocatalyst exhibited improved electrochemical performances for supercapacitors application and demonstrated better electrocatalytic activity for ORR. For this electrocatalyst, the maximum specific capacitance of 266.7 F g−1 was obtained in 1 M KOH at scan rate of 5 mV s−1. Additionally, it has superior catalytic activity and stability via 4-electron process during ORR in the alkaline solution. The contribution of highly intact spherical/hollow structure, good surface area, and large contents of graphitic/pyridinic nitrogen of HN–CMs can improve the mass transportation by facilitating the diffusion pathways which results in the enhancement of its electrochemical and electrocatalytic properties. As a metal–free and cost–effective electrode material, this is supposed to be promising for supercapacitors and fuel cells. Graphical abstract Unlabelled Image Highlights • The core–shell microspheres of PS@PANI are prepared by a template method. • The PS@PANI is carbonized to obtain the hollow nitrogen–doped carbon microspheres (HN–CMs). • HN–CMs have the larger surface area, high pore volume, and nitrogen–incorporated defects of graphitic carbon structure. • It shows excellent electrochemical properties towards supercapacitors and excellent electrocatalytic activity towards ORR. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the impact of the defects/defect density of electrocatalysts on the activity in the triiodide (I3−) reduction reaction of dye‐sensitized solar cells (DSSCs) is indispensable for the design and construction of high‐efficiency counter electrodes (CEs). Active‐site‐enriched selenium‐doped graphene (SeG) was crafted by ball‐milling followed by high‐temperature annealing to yield abundant edge sites and fully activated basal planes. The density of defects within SeG can be tuned by adjusting the annealing temperature. The sample synthesized at an annealing temperature of 900 °C exhibited a superior response to the I3− reduction with a high conversion efficiency of 8.42 %, outperforming the Pt reference (7.88 %). Improved stability is also observed. DFT calculations showed the high catalytic activity of SeG over pure graphene is a result of the reduced ionization energy owing to incorporation of Se species, facilitating electron transfer at the electrode–electrolyte interface. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the impact of the defects/defect density of electrocatalysts on the activity in the triiodide (I3−) reduction reaction of dye‐sensitized solar cells (DSSCs) is indispensable for the design and construction of high‐efficiency counter electrodes (CEs). Active‐site‐enriched selenium‐doped graphene (SeG) was crafted by ball‐milling followed by high‐temperature annealing to yield abundant edge sites and fully activated basal planes. The density of defects within SeG can be tuned by adjusting the annealing temperature. The sample synthesized at an annealing temperature of 900 °C exhibited a superior response to the I3− reduction with a high conversion efficiency of 8.42 %, outperforming the Pt reference (7.88 %). Improved stability is also observed. DFT calculations showed the high catalytic activity of SeG over pure graphene is a result of the reduced ionization energy owing to incorporation of Se species, facilitating electron transfer at the electrode–electrolyte interface. [ABSTRACT FROM AUTHOR]

High mobility, which is highly relevant to crystal structures, is one of the predominant superiorities of organic–inorganic halide perovskites. However, the anisotropy of carrier mobility for this photoelectric material on different crystal planes is still unclear. Based on Marcus theory and Density Functional Theory, we investigated the anisotropy of carrier mobility by calculating the intramolecular vibration (namely, internal recombination energy λ ) and intermolecular electronic coupling integral V along a representative crystal plane. Results show that the electrons and holes exhibit consistency in the transport orientations that are parallel to the (010), (101), and (110) crystal planes. However, inconsistency was observed in those parallel to the (111) and (001) crystal planes (with an angle of approximately 60°) between the electron and hole transport directions This condition is unfavorable to the balancing of the transport and collection of photoinduced carriers. Our work reveals the theoretical significance of control-oriented growth of perovskites. [ABSTRACT FROM AUTHOR]

All-solid-state organic-inorganic halide perovskite solar cells (PSCs) have attracted wide attention due to the rapid progress of power conversion efficiency in recent years. Hole transport material (HTM) in PSCs plays the role of extracting and transporting photo-excited holes. Anisotropy of carrier mobility is one important property for semiconductors, however, which still remains unclear for the dominant HTM spiro-OMeTAD used in PSCs. Based on Density Functional Theory (DFT) and Marcus theory, we for the first time conducted investigations on the anisotropy of carrier mobility along representative crystal planes of spiro-OMeTAD by recombination energy λ and electronic coupling integral V . Results indicate that the holes and electrons show transport orientations consistency parallel to the (010), (101) and (111) crystal planes while inconsistency was found parallel to (100), (110), (011) and (001) crystal planes (with an angle ranged from 40° to 70° between the hole and electron transport directions). Our work embodies the theoretical significance of controllable and oriented fabrication of HTM in PSCs. [ABSTRACT FROM AUTHOR]

Interlayer expanded MoS 2 grown on graphene nanoribbon aerogel (GNRA) has been synthesized and used as anode material for high performance lithium and sodium ion batteries (LIBs, SIBs). The edge effect of graphene nanoribbons including the enormous oxygen functional groups and the insertion of edge carbon layers leads to the formation of MoS 2 with large interlayer spacing. The expansion boosts the intercalation and diffusion of alkaline ions (Li + and Na + ) in layered MoS 2 . As tested for LIBs, the MoS 2 /GNRA electrodes exhibit excellent rate performance as capacity of 303 mAh g −1 can still be achieved even at a high current density of 30 A g −1 . Long cycling performance for 1800 cycles at 10 A g −1 further confirms their superior stability. The hybrid structures also show good performance for SIBs, specific capacities of 372–203 mAh g −1 are obtained at a current density range of 0.5–15 A g −1 . A capacity of 158 mAh g −1 is still kept even after 1500 cycles at 5 A g −1 . This work provides a facile method to control the structure of layered metal sulfides and confirms their potential applications in energy storage and conversion. [ABSTRACT FROM AUTHOR]

Absract Utilization of metal oxide/supports interface structures could generate high- performance electrochemical materials for clean energy storage and conversion. However, designing the metal oxide/supports interfaces with highly enhanced conductivity and cycle durability remains a significant challenge. Here, we demonstrate an in-situ growth technique to synthesize a Sn/SnO 2 @C composite with nano-Sn species attached on surface of carbon spheres (denoted as Sn/SnO 2 @C) during the carbonization of a sol-gel precursors of tin (IV) tetrachloride pentahydrate (SnCl 4 ·5H 2 O) and Resorcinol-Formaldehyde (Sn 4+ -RF) in N 2 . We investigate the nucleation and crystal growth of Sn/SnO 2 from Sn 4+ -RF precursor to Sn/SnO 2 @C composite with the variation of the concentration of acid value and heat-treatment temperature. Sn/SnO 2 @C-(1.0, 800) composite as supercapacitor electrode achieves a maximum specific capacitance of 906.8 F g −1 at a scan rate of 1 mV s −1 in 6 M KOH solution, and an excellent cycle durability of 2000 cycles at 5 A g −1 . The electrochemical performances demonstrate that charge storage occurs in Sn/SnO 2 @C mainly due to redox reactions between the binary oxidation states: Sn↔Sn(OH) 6 2− (IV) in basic electrolyte, hierarchical porosity and Sn/SnO 2 @C distinct structure, which is formed in situ. The work provides new insights into the rational design of Sn@C composites electrode materials for pseudocapacitor and other electrochemical devices. [ABSTRACT FROM AUTHOR]

Novel composites made of two dimensional (2D) MoS 2 nanosheets and graphene (G) have been fabricated by a combined approach of chemical vapor deposition and hydrothermal technique. The G film helps to mediate the growth and dispersion of MoS 2 nanosheets, of which the unique role of G in the MoS 2 growth is revealed by density functional theory study. The results show that the hexagonal lattice carbon of the G film can easily interact with sulfur species derived from reaction precursors, which favors the uniform growth of 2D MoS 2 . The unique function of the G film demonstrated here can be extended to other carbon substrates for growing 2D MoS 2 nanosheets. The G-MoS 2 composites consisting of two types of 2D materials are tested as the binder-free counter electrodes (CEs) for dye-sensitized solar cells, showing a high power conversion efficiency of 7.1% that is comparable to the expensive Pt CEs. The 2D G film in the hybrids has two functions: the active sites for dispersing the electrochemically active MoS 2 crystals and the high electrical conducting matrix for fast charge transfer. This synergistic effect may help to shed a light on the functionalization of other inorganic materials to G for advanced energy applications. [ABSTRACT FROM AUTHOR]

Nitrogen-doped porous carbons (NPCs) with high hydrogen sulfide (H 2 S) adsorption capacity have been prepared through the molten-salt approach, using d -glucose as carbon source, melamine as nitrogen source and eutectic salt (LiCl/KCl) as porogen. The NPCs possess tunable nitrogen content (3.07–24.31 wt.%) and specific surface area (451–1190 m 2 /g) with the changing of the weight ratio of nitrogen source to carbon source and synthesis temperature. The H 2 S adsorptive performance of NPCs is highly superior to that of non-doped porous carbon. X-rays photoelectron spectroscopy analyses combined with quantum chemical calculations demonstrate that the adsorption performance of the as-prepared NPCs depends on their nitrogen content and N-bonding configurations in the carbon materials, as well as their porosity. Pyridinic nitrogen doped carbon in NPCs have stronger interaction with H 2 S compared to pyrrolic and graphitic nitrogen doped carbon. Based on the advantages of the developed porosity and abundant nitrogen functional groups, the saturated sorption capacities of 0.97–1.25 mmol H 2 S/g can be achieved over NPCs at 25 °C under dry and anaerobic conditions. [ABSTRACT FROM AUTHOR]