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Angle-resolved XPS combined with argon ion etching was used to characterize the surface functional groups and the chemical structure of Ti3C2Tx MXene. Survey scanning obtained on the sample surface showed that the sample mainly contains C, O, Ti and F elements, and a little Al element. Analyzing the angle-resolved narrow scanning of these elements indicated that a layer of C and O atoms was adsorbed on the top surface of the sample, and there were many O or F related Ti bonds except Ti–C bond. XPS results obtained after argon ion etching indicated staggered distribution between C–Ti–C bond and O–Ti–C, F–Ti bond. It is confirmed that Ti atoms and C atoms were at the center layer of Ti3C2Tx MXene, while O atoms and F atoms were located at both the upper and lower surface of Ti3C2 layer acting as surface functional groups. The surface functional groups on the Ti3C2 layer were determined to include O2−, OH−, F− and O−–F−, among which F atoms could also desorb from Ti3C2Tx MXene easily. The schematic atomic structure of Ti3C2Tx MXene was derived from the analysis of XPS results, being consistent with theoretical chemical structure and other experimental reports. The results showed that angle-resolved XPS combing with argon ion etching is a good way to analysis 2D thin layer materials.

While using hydride precursors, such as TiH

The classical size effect of Pt particles on oxygen reduction reaction (ORR) suggests that the activity and durability would decrease with reducing the particle size, self-limiting the effectiveness in maximizing the Pt utilization efficiency with the particle-size-reduction strategy. Herein, we discover an anomalous size effect based on Pt nanowires (NWs) with tunable diameters, where the monotonically increasing activity and durability for ORR were observed with decreasing the diameter from 2.4 to 1.1 nm. Our results reveal that the dominant role of increased compressive strain induced by decreasing the diameter of NWs in weakening the adsorption and suppressing the Pt dissolution accounts for this anomalous size effect, where the reduced low-coordinated sites on NWs, the intrinsic structural advantage, is the root. Our findings not only expand the knowledge to the classical size effect but also provide new implications to break through the size limit in the design of Pt-based ORR catalysts.

The ecological devastation observed in the 21st century requires everyone’s participation, including corporates. Many companies have, therefore, incorporated these ecological concerns into their sustainability decisions. We reviewed studies on the nexus of ecological and entrepreneurial sustainability in the context of corporates (large enterprises). The review focuses on clarifying concepts and building a conceptual framework to enhance a better and comprehensive understanding of the ecological side of corporate entrepreneurship sustainability. Through a systematic review of 53 selected papers, we provide inputs for integrating the ecological aspects into company policies and philosophy, in order to build a green business that balances business opportunities with environmental commitments. The study initiates new research agendas by creating a new construct—sustainable corporate ecological entrepreneurship (SCEE).

The current catalytic reaction mechanism for ammonia synthesis relies on either dissociative or associative routes, in which adsorbed N2 dissociates directly or is hydrogenated step-by-step until it is broken upon the release of NH3 through associative adsorption. Here, we propose a concerted mechanism of associative and dissociative routes for ammonia synthesis over a cobalt-loaded nitride catalyst. Isotope exchange experiments reveal that the adsorbed N2 can be activated on both Co metal and the nitride support, which leads to superior low-temperature catalytic performance. The cooperation of the surface low work function (2.6 eV) feature and the formation of surface nitrogen vacancies on the CeN support gives rise to a dual pathway for N2 activation with much reduced activation energy (45 kJ·mol-1) over that of Co-based catalysts reported so far, which results in efficient ammonia synthesis under mild conditions.

Hydrogen generation from water-gas shift (WGS) reaction requires the import of secondary energy, making it unsuitable for large scale applications. Herein, we present a new scalable system consisting of new photothermal device and catalysts that can produce hydrogen via the WGS reaction with zero additional energy import. The new photothermal device based on a chromium film can completely absorb sunlight, fully convert sunlight to heat energy and localize the heat energy synergistically, which makes a high temperature of 305 °C under one standard sunlight irradiation. The catalysts are scalable CuOx/ZnO/Al2O3 nanosheets (2D CuZnAl) with high WGS activity, which were synthesized via the surfactant effect of boric acid. The 2D CuZnAl could be heated to 297 °C under one standard solar irradiation with the new photothermal device. This new system shows a hydrogen production rate of 192.33 mmol g−1 h−1 under one standard sunlight irradiation, 402 times to that of the current record of the one sunlight-driven WGS reaction. Moreover, this new system could be amplified to industrial scale with 4.2 m2 of irradiated area and was able to generate 6.60 m3 of hydrogen from the WGS reaction solely driven by outdoor sunlight in the daytime of spring as well as realized a zero emission of CO2 with the help of a greenhouse agriculture. This study introduces a scalable, highly efficient zero CO2 emission and stable route of outdoor sunlight-driven hydrogen generation from the WGS reaction.

Metal sulphide electrocatalyst is considered as one of the most promising low-cost candidates for oxygen evolution reaction (OER). In this work, we report a novel free-standing Cu2S branch array via a facile TiO2-induced electrodeposition-sulfurization method. Interestingly, cross-linked Cu2S nanoflake branch is strongly anchored on the TiO2 backbone forming high-quality Cu2S/TiO2/Cu2S core-branch arrays. The branch formation mechanism is also proposed. As compared to the pure Cu2S nanowire arrays, the as-prepared Cu2S/TiO2/Cu2S core-branch arrays show much better alkaline OER performance with lower overpotential (284 mV at 10 mA cm−2) and smaller Tafel slope (72 dec−1) as well as enhanced long-term durability mainly due to larger exposed area and more active electrocatalytic sites. Our work provides a new way for construction of advanced metal sulphide electrocatalysts for electrochemical energy conversion.

Rational design of cost-effective high-performance electrocatalysts for oxygen evolution reaction (OER) is of great significance for electrochemical water splitting. Herein, we adopt a nitrogen doping method to fabricate self-supported N-doped CoO nanowire arrays (N–CoO) as active electrocatalysts via a facile hydrothermal combined doping method. The N–CoO nanowires are strongly composited with the carbon cloth substrate forming free-standing electrode with reinforced stability and high electronic conductivity. Owing to the increased accessible and electroactive areas, rich/short pathways for charge transfer and enhanced electronic conductivity, the N–CoO electrode exhibits excellent electrocatalytic performance for OER with a low overpotential (319 mV at 10 mA cm−2 and 410 mV at 100 mA cm−2) and a low Tafel slope of 74 mV dec−1 as well as superior long-term stability with no decay in 24 h continuous test in alkaline solution. Our reported design and optimization strategy provide a promising way to construct interesting well-aligned arrays for application in energy storage and conversion.

Summary Although perovskite has been widely explored in optoelectronic devices, it has been rarely explored as a Schottky junction. Here, we demonstrate a light- and mechanical-energy co-harvesting generator based on a dynamic metal/perovskite Schottky junction. In dark conditions, by moving Al over perovskite film (conductivity: 70.0 S/cm), output voltage and current density of −0.70 V and −41.1 A/m2, respectively, are achieved. As defects eliminate the photo-generated carriers in the static metal/perovskite junction under light illumination, the photoresponse is negligible. Strikingly, the output current of dynamic metal/perovskite junction under light illumination is enhanced by 3-fold compared with the dynamic junction in the dark condition. This nonlinear photo-enhanced effect is proposed as a result of strong interaction between the photo-generated and bound back carriers in the dynamic Schottky junction as well as the high light-absorption coefficient of perovskite. A flexible Al/perovskite generator has been demonstrated as a wearable energy-harvesting device.

We describe the synthesis of the new ternary compound CaRuSi whose chemical and physical properties help draw a clear picture of how electronic structure controls the behavior of an isostructural series of intermetallics. DFT calculations reveal that an electronic pseudogap arises near the Fermi level (EF), corresponding to 14 valence electrons per RuSi unit. The closed-shell-like character is further investigated by comparisons with the electronic structures of CaCoSi (15 electrons), where the EF lies above the corresponding pseudogap, and its hydride CaCoSiH, where formation of H anions restores the 14-electron count on the metal sublattice, returning the EF to the pseudogap. The chemical origin of the 14-electron pseudogap is interpreted with a reversed approximation Molecular Orbital analysis. Here, the pseudogap is shown to coincide with the filling of Ru 16 electron configurations isolobal to the d8 square planar complexes of coordination chemistry (but where 4 electron pairs are shared covalently b...

Intermetallic silicide compounds, LaScSi and Y$_5$Si$_3$, known for being hydrogen (H) storage materials, are drawing attention as candidates for electrides in which anions are substituted by unbound electrons. It is inferred from a muon spin rotation experiment that the local field at the muon site (which is the same site as that for H) in these compounds exhibits a large negative shift under an external magnetic field, which is mostly independent of temperature. Such anomalous diamagnetism signals a unique property of electride electrons associated with transition metals. Moreover, the diamagnetic shift decreases with increasing H content, suggesting that the electride electrons existing coherently in the hollow interstitial positions are adsorbed by H to form hydride ions (H$^-$), 6 pages, 5 figures

Photo-induced phase transitions have been intensively studied owing to the ability to control a material of interest in the ultrafast manner, which can induce exotic phases unable to be attained at equilibrium. However, the key mechanisms are still under debate, and it has currently been a central issue how the couplings between the electron, lattice, and spin degrees of freedom are evolving during photo-induced phase transitions. Here, we develop a new analysis method, frequency-domain angle-resolved photoemission spectroscopy, to gain precise insight into electron-phonon couplings during photo-induced insulator-to-metal transitions for Ta$_2$NiSe$_5$. We demonstrate that multiple coherent phonons generated by displacive excitations show band-selective coupling to the electrons. Furthermore, we find that the lattice modulation corresponding to the 2 THz phonon mode, where Ta lattice is sheared along the a-axis, is the most relevant for the photo-induced semimetallic state.

The excitonic insulator Ta$_2$NiSe$_5$ experiences a first-order structural transition under pressure from rippled to flat layer-structure at Ps = 3 GPa, which drives the system from an almost zero-gap semiconductor to a semimetal. The pressure-induced semimetal, with lowering temperature, experiences a transition to another semimetal with a partial-gap of 0.1-0.2 eV, accompanied with a monoclinic distortion analogous to that occurs at the excitonic transition below Ps. We argue that the partial-gap originates primarily from a symmetry-allowed hybridization of Ta-conduction and Ni-valence bands due to the lattice distortion, indicative of the importance of electron-lattice coupling. The transition is suppressed with increasing pressure to Pc = 8 GPa. Superconductivity with a maximum Tsc = 1.2 K emerges around Pc, likely mediated by strongly electron-coupled soft phonons. The electron-lattice coupling is as important ingredient as the excitonic instability in Ta2NiSe5., Comment: 6 pages, 4 figures

Ammonia is one of the most important feedstocks for the production of fertilizer and as a potential energy carrier. Nitride compounds such as LaN have recently attracted considerable attention due to their nitrogen vacancy sites that can activate N

In this work, g-C3N4@TiO2 nanostructures with hollow sphere morphology, small grain size, high crystalline quality, and high surface area are successfully synthesized by the annealing method using melamine and hollowsphere precursor, which could be a universal method to synthesis hollow sphere nanoheterojunction. Excellent photocatalytic property was observed from the as-prepared g-C3N4@TiO2 nanostructure with 466.43 μmol·g–1·h–1 hydrogen generation rate under visible light irradiation (>420 nm), which was 5.5 times as much as the control couple, nanoparticle nanoheterojunction g-C3N4@TiO2. No apparent deactivation was found during the follow-up cycle performance test. The special morphology and the heterojunction construction contribute to both visible light absorption and photogenerated electron–hole pair separation efficiency and finally to the photocatalytic property. The content of g-C3N4 was proved to be an important parameter for the promotion of the photocatalytic property. Overlarge content may l...

Atomically ordered intermetallic nanocrystals have been extensively explored in electrocatalysis due to their outstanding catalytic performances and excellent stabilities. However, controllable synthesis of intermetallic nanocrystals in terms of their size and structure remains a grand challenge due to the generally involved high-temperature thermal annealing synthetic method, largely hindering the optimization of their catalytic properties. Herein, we report a versatile approach to the synthesis of atomically ordered Pd3Pb multiply twinned intermetallic nanowire networks (MT-IM-NNs) with a tunable diameter and microstructure. The use of preformed Pd seeds, which were converted to a Pd3Pb intermetallic phase via the diffusion of Pb atoms into the seeds, as well as an oriented attachment growth mode, accounted for the formation of such a unique structure. Importantly, the diameter and microstructure of Pd3Pb MT-IM-NNs could be engineered by controlling the size and type of Pd seeds. In addition, the Pd3Pb multiply twinned intermetallic porous nanowire networks exhibited a high faradaic efficiency of 21.46% and an NH3 yield rate of 18.2 μg h−1 mgcat−1 at −0.2 V vs. the reversible hydrogen electrode toward N2 electroreduction.

Ruthenium (Ru) loaded catalysts are of significant interest for ammonia synthesis under mild reaction conditions. The B5 sites have been reported as the active sites for ammonia formation, i.e., Ru with other coordinations were inactive, which has limited the utilization efficiency of Ru metal. The implantation of Ru into intermetallic compounds is considered to be a promising approach to tune the catalytic activity and utilization efficiency of Ru. Here we report an acid-durable electride, LnRuSi (Ln = La, Ce, Pr and Nd), as a B5-site-free Ru catalyst. The active Ru plane with a negative charge is selectively exposed by chemical etching using disodium dihydrogen ethylenediaminetetraacetate (EDTA-2Na) acid, which leads to 2–4-fold enhancement in the ammonia formation rate compared with that of the original catalyst. The turnover frequency (TOF) of LnRuSi is estimated to be approximately 0.06 s−1, which is 600 times higher than that of pure Ru powder. Density functional theory (DFT) calculations revealed that the dissociation of N2 occurs easily on the exposed Ru plane of LaRuSi. This systematic study provides firm evidence that layered Ru with a negative charge in LnRuSi is a new type of active site that differs significantly from B5 sites.

2D magnets and their engineered magnetic heterostructures are intriguing materials for both fundamental physics and application prospects. On the basis of the recently discovered intrinsic magnetic topological insulators (MnBi

Discovering an active and durable catalyst for oxygen reduction reaction is crucial to the commercialization of fuel cells, but remains grand challenging. Here we report, for the first time, the trace doping of early transition metal (ETM) Re into ultrathin PtNiGa nanowires (Re-PtNiGa NWs) to construct a novel catalyst integrating the superior activity, long-time durability, and high utilization efficiency of Pt atoms. Impressively, the Re-PtNiGa tetrametallic NWs present a 19.6-fold enhancement in mass activity (3.49 A mg−1Pt) compared to commercial Pt/C catalyst and only a 10.6% loss in mass activity after 20,000 cycles of durability test. Moreover, the real fuel cell assembled by Re-PtNiGa NWs on the cathode strongly supports its great potential in fuel cells. The density functional theory calculations reveal that introduction of ETM Re into PtNiGa NWs could weaken binding strength of oxygenated species and elevate dissolution potential, well rationalizing the great enhancements in activity and durability.

We report the successful synthesis of LaCu0.67Si1.33 and Y5Si3 electride nanoparticles (NPs) using the Ar/H2 arc evaporation technique. The obtained particle sizes are 10–50 nm in diameter, and their surface areas are enhanced by orders of magnitude compared with hand-milled samples. Their catalytic performances were indeed improved by a factor of 60 for the hydrogenation of nitrobenzene (LaCu0.67Si1.33) and 3 for ammonia synthesis (Ru-loaded Y5Si3). This marked difference in the enhancement of catalytic activities between each system can be attributed to the geometric structure of active sites. These results show that the Ar/H2 arc evaporation technique offers wide versatility for the preparation of rare-earth-based electride NPs with enhanced catalytic activities.

The ceramic coatings on the surface of aluminum alloy substrates with micro-grooves have been successfully fabricated in the silicate solution via micro-arc oxidation (MAO) approach. Microstructure characterization showed that the larger main discharge channels were located in the center of micro-groove, the smaller secondary discharge channels were located on both sides of main discharge channel; and a few irregular micro-pores existed in the vicinity of all discharge channels, which were mainly cause by the rapid cooling and solidification of discharge channels hindering the removal of gases produced via reaction. Moreover, the growing direction of coating in the initial stage was mainly outward-growth and resulted in the formation of inverted triangle coating structure, which was due to the sharp-angled effect. But in the final growing stage, the inward-growth behavior played a key role owing to the spark transfer. According to above results and discussion, the formation of smooth, uniform and homogeneous ceramic coating on the surface of whole trapezoidal micro-groove substrate contained four stages: anodic oxidation growth, sharp corner rapid growth, coating homogenization and groove self-filling.

Ammonia (NH

Cervical cancer is the third leading cause of female death in the world. Serum microRNAs (miRNAs) are currently considered to be valuable as noninvasive cancer biomarkers, but their role in the prognosis of cervical cancer has not been elucidated. We aimed to find serum miRNAs that can be used as prognostic factors for cervical cancer. A traumatic pathological biopsy is the only reliable method for determining the severity of cervical cancer currently. Thus, noninvasive diagnostic markers are needed. The serological expression of candidate miRNAs were measured in 90 participants, including 60 patients with cervical cancer and 50 patients with cervical intraepithelial neoplasia. Two patients with cervical cancer were excluded from the study because of lack of data. miRNAs were evaluated by quantitative reverse transcription polymerase chain reaction. miR-143/-4636 appeared specific for cervical cancer compared with cervical intraepithelial neoplasia (P < .001). The classification performance of validated miRNAs for cervical cancer [Area under the receiver operating characteristic curve (AUC) = 0.942] was better than that reached by squamous cell carcinoma antigen (SCC-Ag; AUC = 0.727). Poor-differentiation group has lower miR-143/-4636 levels in serum (P < .05). miR-4636 level was correlated gross tumor volume and the depth of invasion (P < .0001). In our study, we found a combination of miR-143 and miR-4636 that is independently and strongly associated with cervical cancer prognosis and can be used as a clinically prognostic factor.

In this paper, Na-doped ZnO thin films were grown by MOCVD using cyclopentadienylsodium (CpNa) as the sodium source. The effects of substrate temperature and sodium source temperature on the properties of Na-doped ZnO thin films were studied. SIMS measurement verified that higher substrate temperature would result in higher Na doping content in ZnO:Na thin films. SEM and Hall measurements revealed that both surface morphology and electrical properties of ZnO:Na thin films showed nonlinear variation with substrate temperature and sodium source temperature. When the substrate temperature or the sodium source temperature was increased, the surface morphology of ZnO:Na thin films turned to sheet structures tilted in all directions first and then back to perpendicular hexagonal structure dominant morphology, and the hole concentration increased first and then decreased. This nonlinear variation trend was ascribed to be related to the variation of doping content and impurity position in ZnO:Na thin films, especially the Na impurity position.

Metal doping has been demonstrated to be an effective strategy to modulate photocatalytic properties. However, it is very challenging to achieve tunable electronic structures and controllable morphologies with more active sites only via metal doping. Herein, Zr doped CaTiO3 photocatalysts with enhanced photocatalytic activities toward the hydrogen evolution was prepared by one-step mild hydrothermal reaction. We revealed that zirconium doping would regulate the surface structures of CaTiO3 from smooth surface to characteristic nanosteps structures. This nanosteps structure with more exposed active sites accompanied by higher exposed surface area, oxygen vacancies and reduction ability, effectively promote the separation of photo-induced carriers, thus resulting in increased photocatalytic properties. This work provides a guideline for surface structures and electronic structures modification simultaneously to design powerful photocatalysts only by metal doping.

In this study we synthesize a novel mesoporous titanium oxide (TiO2) through calcination of a bioinspired supramolecular assembly of polymeric micelles, based on the thymine-functionalized homopolymer, poly(4-vinylbenzyl triazolylmethyl-methylthymine), complexed with Ti(OH)(2)(2+) ions. We characterize thin films of these structures using wide-angle X-ray diffraction, small-angle X-ray scattering, nitrogen adsorption/desorption isotherms, transmission electron microscope, and scanning electron microscope. This approach is simple, effective, and inexpensive when compared with the synthesis of diblock or triblock copolymers typically required to prepare soft templates. This new mesoporous material exhibits superior photocatalytic activity for the degradation of the organic dye methylene blue almost three times higher than that of bulk TiO2.

Clove essential oil (CEO) is a promising alternative to chemical fungicides for postharvest decay control. However, relatively high concentrations required for in vivo microbial growth inhibition limit its application. Hence, this study aimed to strengthen the antifungal activity of CEO by loading it in microemulsion system. Two CEO microemulsions (ME-1, CEO/ethanol/Tween 80 = 1:2:7; ME-2, CEO/ethanol/Tween 80 = 1:3:6) were evaluated their antifungal activity against Penicillium digitatum in vitro and in navel oranges. Microemulsification of CEO caused a reduction of MIC (minimum inhibitory concentration) from 0.50 μl/ml to 0.25 μl/ml, while the MFC (minimum fungicidal concentration) remained unchanged at 0.50 μl/ml, indicating enhancement of only fungistatic activity. The decay incidence of navel oranges treated with ME-1 and ME-2 was significantly ( p P . digitatum . The enhanced control of postharvest green mold of navel oranges by CEO after microemulsification can broaden its application in food industry.

We report an air and water stable electride Y5Si3 and its catalytic activity for direct ammonia synthesis. It crystallizes in the Mn5Si3-type structure and confines 0.79/f.u. anionic electrons in the quasi-one-dimensional holes. These anionic electrons strongly hybridize with yttrium 4d electrons, giving rise to improved chemical stability. The ammonia synthesis rate using Ru(7.8 wt %)-loaded Y5Si3 was as high as 1.9 mmol/g/h under 0.1 MPa and at 400 °C with activation energy of ∼50 kJ/mol. Its strong electron-donating ability to Ru metal of Y5Si3 is considered to enhance nitrogen dissociation and reduce the activation energy of ammonia synthesis reaction. Catalytic activity was not suppressed even after Y5Si3, once dipped into water, was used as the catalyst promoter. These findings provide novel insights into the design of simple catalysts for ammonia synthesis.

We have measured anisotropic electrical resistivity of quasi-one-dimensional Ta2NiSe5 single crystals under pressure. While the in-plane anisotropy is almost pressure independent, the inter-plane one greatly decreases at P c ∼ 3 GPa accompanied by a pressure-induced semiconductor-semimetal transition. Nevertheless, a similar anomaly in the temperature dependence of in-plane anisotropy has been observed in each phase. This anomaly in the low-pressure phase below P c is regarded as an excitonic transition, and thus both of these anomalies are suppressed with increasing pressure. These results suggest that the suppression of the excitonic binding energy with pressure is caused by the increase of free carrier densities and the inter-plane conductivity.

In this work, g-C

2D magnets and their engineered magnetic heterostructures are intriguing materials for both fundamental physics and application prospects. On the basis of the recently discovered intrinsic magnetic topological insulators (MnBi2 Te4 )(Bi2 Te3 )n , here, a new type of magnet, in which the magnetic layers are separated by a large number of non-magnetic layers and become magnetically independent, is proposed. This magnet is named as a single-layer magnet, regarding the vanishing interlayer exchange coupling. Theoretical calculations and magnetization measurements indicate that, the decoupling of the magnetic layers starts to emerge from n = 2 and 3, as revealed by a unique slow-relaxation behavior below a ferromagnetic-type transition at Tc = 12-14 K. Magnetization data analysis shows that the proposed new magnetic states have a strong uniaxial anisotropy along the c-axis, forming an Ising-type magnetic structure, where Tc is the ordering temperature for each magnetic layer. The characteristic slow relaxation, which exists only along the c-axis but is absent along the ab plane, can be ascribed to interlayer coherent spin rotation and/or intralayer domain wall movement. The present results will stimulate further theoretical and experimental investigations for the prototypical magnetic structures, and their combination with the topological surface states may lead to exotic physical properties.

Pyrolysis dynamics of graphene oxide (GO) is critical for composite material design, and a few experimental evaluations were conducted so far since extremely high temperature condition is needed. In this work, with help of ReaxFF reactive molecular dynamics simulations, the pyrolysis mechanisms of GO were investigated from two aspects: (1) the structural evolutions of the carbon skeleton and (2) the desorption of the superficial functional groups. At low temperature, desorption of functional groups is dominant, and little point defects or vacancies are introduced to the carbon skeleton. Meanwhile, generation of a number of pyrolysis products was confirmed at higher temperatures. Accordingly, the carbon skeleton is significantly disordered, resulting in an amorphous transformation. Analysis of bonds breaking ratio, hybridization types of carbon atoms and pyrolytic fragments indicated that the restored sp2-hybridized carbons increase with the increasing annealing time, and structure of final products are controlled by hydroxyl and oxygen dangling bonds. Finally, annealing process of GO with different oxygenal group density (R) and OH/O ratio are quantitatively analyzed and found pyrolysis is R and OH/O ratio dependent. These results uncover the pivotal role of oxygen and hydrogen in pyrolysis, and provide a guidance for heat resistant composite designs.