Dissociation Energy Research Articles

Synthesis and structural investigation of salts of 2-amino-3-methylpyridine with carboxylic acid derivatives: an experimental and theoretical study.

The salts bis(2-amino-3-methylpyridinium) fumarate dihydrate, 2C6H9N2+·C4H2O22-·2H2O (I), and 2-amino-3-methylpyridinium 5-chlorosalicylate, C6H9N2+·C7H4ClO3- (II), were synthesized from 2-amino-3-methylpyridine with fumaric acid and 5-chlorosalicylic acid, respectively. The crystal structures of these salts were characterized by single-crystal X-ray diffraction, revealing protonation in I and II by the transfer of a H atom from the acid to the pyridine base. In the crystals of both I and II, N-H...O interactions form an R22(8) ring motif. Hirshfeld surface analysis distinguishes the interactions present in the crystal structures of I and II, and the two-dimensional (2D) fingerprint plot analysis shows the percentage contribution of each type of interaction in the crystal packing. The volumes of the crystal voids of I (39.65 Å3) and II (118.10 Å3) have been calculated and reveal that the crystal of I is more mechanically stable than II. Frontier molecular orbital (FMO) analysis predicts that the band gap energy of II (2.6577 eV) is lower compared to I (4.0035 eV). The Quantum Theory of Atoms In Molecules (QTAIM) analysis shows that the pyridinium-carboxylate N-H...O interaction present in I is stronger than the other interactions, whereas in II, the hydroxy-carboxylate O-H...O interaction is stronger than the pyridinium-carboxylate N-H...O interaction; the bond dissociation energies also confirm these results. The positive Laplacian [∇2ρ(r) > 0] of these interactions shows that the interactions are of the closed shell type. An in-silico ADME (Absorption, Distribution, Metabolism and Excretion) study predicts that both salts will exhibit good pharmacokinetic properties and druglikeness.

Quadruple bonds in MoC: Accurate calculations and precise measurement of the dissociation energy of low-lying states of MoC.

In the present work, the electronic structure and chemical bonding of the MoC X3Σ- ground state and the six lowest excited states, A3Δ, a1Γ, b5Σ-, c1Δ, d1Σ+, and e5Π, have been investigated in detail using multireference configuration interaction methods and basis sets, including relativistic effective core potentials. In addition, scalar relativistic effects have been considered in the second order Douglas-Kroll-Hess approximation, while spin-orbit coupling has also been calculated. Five of the investigated states, X3Σ-, A3Δ, a1Γ, c1Δ, and d1Σ+, present quadruple σ2σ2π2π2 bonds. Experimentally, the predissociation threshold of MoC was measured using resonant two-photon ionization spectroscopy, allowing for a precise measurement of the dissociation energy of the ground state. Theoretically, the complete basis set limit of the calculated dissociation energy with respect to the atomic ground state products, including corrections for scalar relativistic effects, De(D0), is computed as 5.13(5.06) eV, in excellent agreement with our measured value of D0(MoC) of 5.136(5) eV. Furthermore, the calculated dissociation energies of the states having quadruple bonds with respect to their adiabatic atomic products range from 6.22 to 7.23eV. The excited electronic states A3Δ2 and c1Δ2 are calculated to lie at 3899 and 8057 cm-1, also in excellent agreement with the experimental values of DaBell et al., 4002.5 and 7834 cm-1, respectively.

Selective Photoreforming of Waste Plastics into Diesel Olefins via Single Reactive Oxygen Species

AbstractThe accumulation of plastic waste poses a pressing environmental challenge. Catalytic conversion stands out as an ideal approach for plastics upcycling, particularly through solar‐driven plastics photoreforming. However, due to the common effects of multiple reactive oxygen species (ROS), selectively generating high‐value chemicals becomes challenging. In this study, we developed a universal strategy to achieve >85 % selective production of diesel olefins (C15–C28) from polyolefin waste plastics via single ROS. Using tetrakis (4‐carboxyphenyl) porphyrin supramolecular (TCPP) with different central metals as an example to regulate single ROS generation, results show Ni‐TCPP facilitates triplet exciton production, yielding 1O2, while Zn‐TCPP generates ⋅O2− due to its strong built‐in electric field (IEF). 1O2 directly dechlorinates polyvinyl chloride (PVC) due to the electro‐negativity of chlorine atoms and the low dissociation energy of C−Cl bonds, while ⋅O2− promotes direct dehydrogenation of polyethylene (PE) due to the electro‐positivity of hydrogen atoms and the high dissociation energy of C−H bonds. This method is universally applicable to various single ROS systems. Installation experiments further affirm the application potential, achieving the highest diesel olefin production of 76.1 μmol h−1. Such a universally adaptive approach holds promise for addressing the global plastic pollution problem.

Effect of Ce0.6Zr0.4O2 nanocrystals on boosting hydrogen storage performance of MgH2

Magnesium hydride (MgH2) has been widely recognized as a highly promising solid-state media for hydrogen storage. However, the high operating temperature and the intrinsic sluggish kinetics hinder the practical application as a portable solid storage carrier. To address this issue, we have successfully fabricated a novel rare earth-containing bimetallic oxide additive, namely Ce0.6Zr0.4O2 nanocrystals, which exhibits a significant catalytic effect in enhancing the hydrogen storage properties of MgH2. By incorporating 7 wt% Ce0.6Zr0.4O2 into MgH2, the modified composite releases hydrogen as low as 201 °C. Furthermore, in an isothermal dehydrogenation test conducted at 270 °C for 8 min, approximately 6.15 wt% of H2 was desorbed. The composites can rapidly recharge hydrogen at a low temperature of 50 °C and 6.02 wt% H2 being absorbed within 3 min at 150 °C under 50.0 bar. Comparatively, the dehydrogenation activation energy of the Ce0.6Zr0.4O2-modified MgH2 significantly decreased compared to MgH2 by ball milling. In addition to its improved hydrogen storage properties, the composite also exhibits excellent cycling stability. Through cyclic de-/rehydrogenation experiments conducted at 270 °C, a capacity retention of 98.9 % was achieved over 20 cycles. This exceptional performance can be attributed to the in-situ formation of the CeH2.73/CeO2-x and ZrO2, which originated from the Ce0.6Zr0.4O2 additive following the first de-/rehydrogenation cycle. The uniform dispersion of the multiphase component nano-sized active species within the MgH2 matrix facilitates charge transfer and accelerates hydrogen diffusion. Density functional theory calculations revealed the dissociation energy barrier and dissociation energy of H2 were alleviated by integrating Zr into CeO2. This work provides valuable insights for further rational designs of novel catalysts by transition metals and rare earths in promoting the commercialization of MgH2.

RuMo nanoalloy confined on N-doped carbon toward efficient alkaline and acidic hydrogen evolution reaction

Noble metal-based electrocatalysts have been demonstrated significant efficiency in the production of hydrogen. However, the sluggish kinetics of the hydrogen evolution reaction (HER) in alkaline media due to high water dissociation energy greatly hinders this electrochemical process. Here, we report a RuMo nanoalloy electrocatalyst mounted on a nitrogen-doped carbon skeleton (RuMo@NC). The RuMo@NC catalyst exhibits excellent HER performance in both alkaline and acidic media, displaying small overpotentials of 18 mV and 14 mV for driving the current density of 10 mA⊡cm−2, respectively. This performance surpasses the majority of noble metal electrocatalysts and 20 % commercial Pt/C. Theoretical calculations reveal that the interaction between Ru and Mo results in a modification of the electronic structure. Consequently, this interaction effectively weakens the adsorption energy of hydrogen on the surface of the RuMo alloy, ultimately improving its catalytic performance in the hydrogen evolution reaction. This work offers new ways to design efficient and economical HER electrocatalysts, advancing the exploration of HER catalysts.

Low-Migration Compounds with Amine Functionality as Coinitiators of Radical Polymerization.

The utilization of two-component systems comprising camphorquinone (CQ) and aromatic amines has become prevalent in the photopolymerization. However, there are still concerns about the safety of this CQ/amine system, mainly because of the toxicity associated with the leaching of aromatic amines. In light of these concerns, this study aims to develop novel coinitiator combinations featuring CQ and amines which cannot be leached out of materials, enabling free radical polymerization of representative dentalmethacrylate resins under blue light irradiation. This approach involves the initial design and analysis of hydrogen donors with low C─H bond dissociation energy through molecular modeling. Subsequently, copolymerizable methacrylate functional groups are incorporated via chemical modification, allowing it to act as both coinitiator and copolymerization monomer to achieve low migrationand leachability properties. This work presents, for the first time, the synthesis of the innovative coinitiator and compares its performance with the benchmark CQ/ethyl-4-dimethylaminobenzoate (EDB)-based photoinitiation system (PIS). The results demonstrate the effectiveness of the newly proposed PIS. Finally, an in-depth investigation is conducted into the reaction mechanism associated with this PIS through molecular orbital calculations and electron spin resonance studies.

Tert‐Butyl as a Functional Group: Non‐Directed Catalytic Hydroxylation of Sterically Congested Primary C−H Bonds

AbstractThe tert‐butyl group is a common aliphatic motif extensively employed to implement steric congestion and conformational rigidity in organic and organometallic molecules. Because of the combination of a high bond dissociation energy (~100 kcal mol−1) and limited accessibility, in the absence of directing groups, neither radical nor organometallic approaches are effective for the chemical modification of tert‐butyl C−H bonds. Herein we overcome these limits by employing a highly electrophilic manganese catalyst, [Mn(CF3bpeb)(OTf)2], that operates in the strong hydrogen bond donor solvent nonafluoro‐tert‐butyl alcohol (NFTBA) and catalytically activates hydrogen peroxide to generate a powerful manganese‐oxo species that effectively oxidizes tert‐butyl C−H bonds. Leveraging on the interplay of steric, electronic, medium and torsional effects, site‐selective and product chemoselective hydroxylation of the tert‐butyl group is accomplished with broad reaction scope, delivering primary alcohols as largely dominant products in preparative yields. Late‐stage hydroxylation at tert‐butyl sites is demonstrated on 6 densely functionalized molecules of pharmaceutical interest. This work uncovers a novel disconnection approach, harnessing tert‐butyl as a potential functional group in strategic synthetic planning for complex molecular architectures.

Tert-Butyl as a Functional Group: Non-Directed Catalytic Hydroxylation of Sterically Congested Primary C-H Bonds.

The tert-butyl group is a common aliphatic motif extensively employed to implement steric congestion and conformational rigidity in organic and organometallic molecules. Because of the combination of a high bond dissociation energy (~ 100 kcal mol-1) and limited accessibility, in the absence of directing groups, neither radical nor organometallic approaches are effective for the chemical modification of tert-butyl C-H bonds. Herein we overcome these limits by employing a highly electrophilic manganese catalyst, [Mn(CF3bpeb)(OTf)2], that operates in the strong hydrogen bond donor solvent nonafluoro-tert-butyl alcohol (NFTBA) and catalytically activates hydrogen peroxide to generate a powerful manganese-oxo species that effectively oxidizes tert-butyl C-H bonds. Leveraging on the interplay of steric, electronic, medium and torsional effects, site-selective and product chemoselective hydroxylation of the tert-butyl group is accomplished with broad reaction scope, delivering primary alcohols as largely dominant products in preparative yields. Late-stage hydroxylation at tert-butyl sites is demonstrated on 6 densely functionalized molecules of pharmaceutical interest. This work uncovers a novel disconnection approach, harnessing tert-butyl as a potential functional group in strategic synthetic planning for complex molecular architectures.

Unveiling the influence of hydrophobicity on inhibiting hydrogen dissociation for enhanced photocatalytic hydrogen evolution of covalent organic frameworks

Covalent organic frameworks (COFs) have gained considerable interest as candidate photocatalysts for hydrogen evolution. In this work, we synthesized β-keto-enamine-based COFs (TpPa-X, TpDB, and TpDTP) to explore the relations between structures and photocatalytic hydrogen evolution. COFs were divided into two groups: (1) TpPa-X with different substituents attached to the TpPa backbone and (2) COFs featuring diamine linkers of varied lengths (TpDB and TpDTP). Experiments and density functional theory (DFT) calculations show that moderate hydrophobicity is favorable for the photocatalytic hydrogen evolution process, and acceptable contact angles are anticipated to range from 65° to 80°. Naturally, there are comprehensive factors that affect photocatalytic reactions, and the regulation of different backbones and substituents can considerably affect the performance of COFs for photocatalytic hydrogen evolution in terms of electronic structure, specific surface area, surface wettability, carrier separation efficiency, and hydrogen dissociation energy. Results show that TpPa-Cl2 (TpPa-X, X = Cl2) demonstrates the highest photocatalytic activity, approximately 14.51 mmol g-1h−1, with an apparent quantum efficiency of 4.62 % at 420 nm. This work provides guidance for designing efficient COF-based photocatalysts.

Modeling and analysis of synergistic phenolic antioxidants in edible oil: Integrating molecular simulation and artificial neural network approach

Oxidation causes edible oil deterioration affecting nutrition and safety. Antioxidants delay aging, but selecting compounds experimentally is time-consuming and arbitrary. Thus, a rapid and rational screening method for synergistic antioxidants is essential. This study evaluates the antioxidant effects and mechanisms of four phenolic antioxidants on the oil matrix using multiscale simulation. Tert-butylhydroquinone (TBHQ) exhibited the lowest dissociation energy (226.92 kJ/mol), followed by flavanol (TP) (233.00 kJ/mol). Syringic acid (CA) showed the smallest mean square displacement value. An artificial neural network (ANN) was established to analyze the synergistic and antagonistic interactions between TBHQ and TP, predicting optimal synergy at 3.6 mg TP and 1.8 mg TBHQ. The relative prediction deviation (RPD) value of the validation set was 3.91, and the relative error production (RER) value was 1.87 %. Fourier transform infrared spectroscopy experiments validated this synergy. This research establishes a screening system for compound antioxidants and models the synergistic effects of phenolic antioxidants in edible oil, offering theoretical and technical support for their application in the food industry.

Molybdenum diselenide/polymeric carbon nitride dual-homojunction photocatalyst with multi-step charge transfer for efficient catalytic carbon dioxide reduction

Due to the high dissociation energy of carbon dioxide (CO2) and sluggish charge transfer dynamics, photocatalytic CO2 reduction with high performance remains a huge challenge. Herein, we report a novel dual-homojunction photocatalyst comprising of cyano/cyanamide groups co-modified carbon nitride (CN-TH) intramolecular homojunction and 1 T/2H-MoSe2 homojunction (denoted as 1 T/2H-MoSe2/CN-TH) for enhanced photocatalytic CO2 reduction. In this dual-homojunction photocatalyst, the intramolecular CN-TH homojunction could promote the intralayer charge separation and transfer owing to the strong electron-withdrawing capabilities of the two-type cyanamide, while the 1 T/2H-MoSe2 homojunction mainly contributes to a promote interlayer charge transport of CN-TH. This could consequently induce a tandem multi-step charge transfer and accelerate the charge transfer dynamics, resulting in enhanced CO2 reduction activities. Thanks to this tandem multi-step charge transfer, the optimized 1 T/2H-MoSe2/CN-TH dual-homojunction photocatalyst presented a high CO yield of 27.36 μmol·g−1·h−1, which is 3.58 and 2.87 times higher than those of 1 T/2H-MoSe2/CN and 2H-MoSe2/CN-TH single homojunctions, respectively. This work provides a novel strategy for efficient CO2 reduction via achieving a tandem multi-step charge transfer through designing dual-homojunction photocatalyst.

Relative reactivity of methyl anisole isomers: An experimental and kinetic modelling study

Due to the current interest in biomass derived carbon neutral fuels and fuel additives for gasoline engines and to the growing need of understanding the fundamentals of gas phase combustion in the context of wildfires, this study investigates the combustion behavior of key components of biomass pyrolysis oils, namely the three methylanisole isomers (ortho-, meta- and para-methylanisole). Specifically, this study presents the first experimental ignition delay time measurements for such fuels using a shock tube and a rapid compression machine. Ignition experiments were carried out for stoichiometric fuel/air mixtures (φ = 1) at compressed pressure pc = 10 and 20 bar, covering a temperature range Tc = 880–1220 K. A kinetic model based on previous efforts in the area of oxygenated aromatic hydrocarbon fuels is proposed to reproduce and interpret the experimental findings, specifically focusing on capturing the observed different reactivity of the three isomers. To this aim, thermodynamic properties of primary intermediates and bond dissociation energies were calculated highlighting relevant differences originated from the relative position of the O–CH3 and –CH3 substituents. In addition, an isomerization pathway specific to the ortho isomer was theoretically investigated and found to motivate the observed higher reactivity with respect to the meta and para isomers

Strategies for Tuning Tensile Strain and Localized Electrons in a Mo‐Doped NiCoCu Alloy for Enhancing Ampere‐Level Current Density HER Performance

AbstractDeveloping high‐activity non‐noble metal catalysts for improving the ability of water dissociation and H* adsorption/desorption in the hydrogen evolution reaction (HER) process in alkaline and neutral electrolytes is essential but remains challenging. Herein, a Mo‐doped NiCoCu alloy with tuned tensile strain and localized electrons is designed and synthesized by combining the solvothermal and annealing methods for achieving ampere‐level HER performance. Theoretical calculation results prove that Mo doping induces lattice tensile strain and localized electrons (electrons from Mo to the Ni/Co/Cu atoms), promoting the adsorption of O* and H* from H2O molecules on the Mo and Co sites and accelerating water dissociation. Therefore, NiCoCu‐Mo0.078/CF (CF = copper foam) shows low water dissociation energy, providing sufficient H* during the HER process. Meanwhile, its H* Gibbs free energy value is near zero, implying a rapid H* adsorption/desorption process. Electrochemical results show that NiCoCu‐Mo0.078/CF achieves better HER intrinsic activity in both a 1.0 m KOH (η−10 /η−1000 = 35/212 mV) and a 1.0 m phosphate buffer solution (η−10 /η−1000 = 24/256 mV) compared to NiCoCu‐Mo0/CF and NiCoCu‐Mo0.163/CF, and it can continuously operate for 100 h at −1000 mA cm−2. This work shows a sustainable way to design high‐performance catalysts for water electrolysis and proposes a well‐performing HER catalyst.

High-Rate and Selective C2H6-to-C2H4 Photodehydrogenation Enabled by Partially Oxidized Pdδ+ Species Anchored on ZnO Nanosheets under Mild Conditions.

Photocatalytic C2H6-to-C2H4 conversion is very promising, yet it remains a long-lasting challenge due to the high C-H bond dissociation energy of 420 kJ mol-1. Herein, partially oxidized Pdδ+ species anchored on ZnO nanosheets are designed to weaken the C-H bond by the electron interaction between Pdδ+ species and H atoms, with efforts to achieve high-rate and selective C2H6-to-C2H4 conversion. X-ray photoelectron spectra, Bader charge calculations, and electronic localization function demonstrate the presence of partially oxidized Pdδ+ sites, while quasi-in situ X-ray photoelectron spectra disclose the Pdδ+ sites initially adopt and then donate the photoexcited electrons for C2H6 dehydrogenation. In situ electron paramagnetic resonance spectra, in situ Fourier transform infrared spectra, and trapping agent experiments verify C2H6 initially converts to CH3CH2OH via ·OH radicals, then dehydroxylates to CH3CH2· and finally to C2H4, accompanied by H2 production. Density-functional theory calculations elucidate that loading Pd site can lengthen the C-H bond of C2H6 from 1.10 to 1.12 Å, which favors the C-H bond breakage, affirmed by a lowered energy barrier of 0.04 eV. As a result, the optimized 5.87% Pd-ZnO nanosheets achieve a high C2H4 yield of 16.32 mmol g-1 with a 94.83% selectivity as well as a H2 yield of 14.49 mmol g-1 from C2H6 dehydrogenation in 4 h, outperforming all the previously reported photocatalysts under similar conditions.

The impact of incorrect dissociation energies on inferred photospheric abundances

ABSTRACT Spectral synthesis codes are essential for inferring stellar parameters and detailed chemical abundances. These codes require many physical inputs to predict an emergent spectrum. Developers adopt the best measurements of those inputs at the time they release their code, but those measurements usually improve over time faster than the software is updated. In general, the impact of using incorrect or uncertain dissociation energies is largely unknown. Here, we evaluate how incorrect dissociation energies impact abundances measured from C2, CN, CH, TiO, and MgO features. For each molecule, we synthesized optical spectra of FGKM-type main-sequence and giant stars using the literature dissociation energy and an incorrect (perturbed) dissociation energy. We find that the uncertainties in the dissociation energies adopted by spectral synthesis codes for CN, CH, TiO, and MgO lead to negligible differences in flux or abundance. C2 is the only diatomic molecule where the uncertainty of the inputted dissociation energy translates to a significant difference in flux and carbon abundance differences of up to 0.2 dex. For solar-like stars, the impact on carbon abundance is up to 0.09 dex. These large abundance differences demonstrate the importance of updating the inputs adopted by spectral synthesis codes, as well as a consensus on appropriate values between different codes.

Derivation of Morse potential

The Morse potential is widely used in chemistry, physics, and material science to describe interatomic interactions. We show that the Morse potential can be derived from a simple screened charge model accounting for the shielding of the nuclear charge by electron density. In this model, the parameter governing the width of the potential is related to the average shielding strength and the exponents of the atomic orbitals used in electronic structure calculations. The parameter representing the bond dissociation energy of a diatomic molecule is derived by combining the quantum mechanical covalent and classical electrostatic interactions. Moreover, the revealed connection between the parameters of the Morse potential and Pauling’s bond order and electronegativity provides insight into the relation between the classical and quantum mechanical descriptions of chemical bonds. This derivation of the Morse potential from the atomic quantities is expected to contribute to the development of the new basis sets incorporating Slater-type orbitals for electronic structure calculations and the transferable reactive force fields for molecular dynamics simulations. Furthermore, this interpretation of the Morse potential helps to understand the relationships between widely used chemical concepts, including effective atomic charge, bond dissociation energy, electronegativity, and bond order.

Exploring factors affecting the dissociation energies of C–O and C–C bonds in lignin oligomers

The bond dissociation energy (BDE) of lignin is a key factor for lignin depolymerization, assisting in revealing the depolymerization mechanism. However, the impact of substituent as well as solvent, which usually stay together, on BDE of lignin remains unclear. Here, density functional theory (DFT) calculation is employed to compute the BDE of C–O and C–C bonds in lignin oligomers with six substituents in four solvents. The relationship models between multiple factors and BDE are established using random forest algorithm, achieving a predictive accuracy of 0.97. The results show that oxidating hydroxyl to ketone benefits the cleavage of β-O-4 and β-1 bonds. Hydroxyl and methoxy effectively contribute to breaking the Cβ-1 and Cα–Cβ bonds in the β-1 dimer. Polar solvents combined with hydroxyl promote C–O bond dissociation, while alkyl-containing solvents favor C–C bond dissociation. These findings provide valuable insights into lignin depolymerization, pre-depolymerization structural modifications, and the prediction of depolymerization pathways.

Nonlinear optical properties of KnCl (n = 2–7) superalkali clusters

The lowest energy structures along with the low lying isomer, stabilities, electronic properties, optical properties and nonlinear optical responses of KnCl (n = 2–7) clusters were studied within the density functional theory. The second order energy difference, dissociation energy and GH-L (HOMO–LUMO gap) point out that KnCl (n = 3, 5, 7) clusters are more stable. The calculated adiabatic ionization energies (AIE) for the KnCl (n = 2–6) clusters are in agreement with the measured ionization energies. The optical properties, namely optical electronegativity and refractive index, depends on the GH-L energy values. The K atom capped planar rhombus geometry of the K4Cl causes the noticeable vibrational frequency shift compared to the rest of IR spectra of the clusters. The first static hyperpolarizability (β o) values are in the range of 2.33 × 103 –2.87 × 104 au and the second static hyperpolarizability varies between 5.74 × 106 au and 38.9 × 106 au for the cluster. The nonlinear optical response is due to the superalkali nature of KnCl (n = 2–7) clusters. From computed β vec values, the hyperpolarizability has projection on the dipole moment vector for the superalkalis except the K2Cl and K5Cl. The absorption spectra point out that KnCl (n = 6–7) clusters can be suitable as a NLO material since they have transparency in the deep UV region (λ< 300 nm).

Ultrahigh Heat/Fire-Resistant, Mechanically Robust, and Closed-Loop Chemical Recyclable Polycarbonate Enabled by Facile Bond Dissociation Energy Modulation.

Plastics serve as an essential foundation in contemporary society. Nevertheless, meeting the rigorous performance demands in advanced applications and addressing their end-of-life disposal are two critical challenges that persist. Here, an innovative and facile method is introduced for the design and scalable production of polycarbonate, a key engineering plastic, simultaneously achieving high performance and closed-loop chemical recyclability. The bisphenol framework of polycarbonate is strategically adjusted from the low-bond-dissociation-energy bisphenol A to high-bond-dissociation-energy 4,4'-dihydroxydiphenyl, in combination with the incorporation of polysiloxane segments. As expected, the enhanced bond dissociation energy endows the polycarbonate with an extremely high glow-wire flammability index surpassing 1025°C, a 0.8mm UL-94V-0 rating, a high LOI value of 39.2%, and more than 50% reduction of heat and smoke release. Furthermore, the π-π stacking interactions within biphenyl structures resulted in a significant enhancement of mechanical strength by as more as 37.7%, and also played a positive role in achieving a lower dielectric constant. Significantly, the copolymer exhibited outstanding closed-loop chemical recyclability, allowing for facile depolymerization into bisphenol monomers and the repolymerized copolymer retains its high heat and fire resistance. This work provides a novel insight in the design of high-performance and closed-loop chemical recyclable polymeric materials.

Cost-efficient sunlight-driven thermoelectric electrolysis over Mo-doped Ni5P4 nanosheets for highly efficient alkaline water/seawater splitting

Thermoelectric water spitting to hydrogen systems has great potential in the production of environment-friendly fuel using renewable solar energy in the future. In this work, we prepared porous nanosheet Mo doping Ni5P4 catalysts on nickel foam with efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in alkaline media. Density Functional Theory (DFT) calculations and experimental studies have shown that Mo doping deadeneds the interaction between H and O atomic orbitals of transition state water molecules, effectively weakening the activation energy of H2O dissociation. Therefore, Mo doping is favorable for enhancing HER activity with overpotential at 10 mA cm–2 of 93 mV and Tafel slope of 40.1 mV dec–1 in 1 M KOH. Besides, it exhibits high alkaline OER activity with an ultra-low overpotential of 200 mV at 10 mA cm–2. Moreover, this catalyst only needs 1.537 V in a dual-electrode configuration of the electrolytic cell, which is much lower than the commercial Pt/C-RuO2 couple (1.614 V). In addition, we have developed and constructed a solar thermoelectric generator (TEG) that is capable of floating on water. This TEG has a continuous power output and an exceptionally long lifespan, providing a stable power supply to the synthesized catalyst electrolyzer. It can produce a maximum power output of over 90 mW, meeting the requirement of converting solar radiation heat into usable electricity. As a result, the system achieves productivity of 0.11 mL min–1 H2. This solar thermal energy conversion technology shows the possibility of large-scale industrial production of H2 and provides a new idea for exploring heat source utilization.