Evolution Of Chemical Structure Research Articles

From cement to geopolymers: Performances and sustainability advantages of ambient curing

The production of Portland cement results in substantial carbon emissions. Geopolymers are regarded as highly promising alternative binder materials to cement due to their low energy consumption and excellent mechanical properties. However, it should be noted that the thermal curing process of geopolymers diminishes their low-carbon advantage. In this study, ground granulated blast furnace slag (GGBS) was used to replace metakaolin (MK) by the ratio of 10 %, 20 %, 30 %, 40 %, and 50 % to produce geopolymers. The aim was to examine the impact of GGBS content on the thermal curing performance of MK-based geopolymers. The microstructure of the specimens was analyzed using SEM and XRD analysis techniques. Lastly, a comprehensive assessment of their sustainability potential was carried out. As a result, slag may increase flow spread, decrease the setting time, and effectively improve the mechanical properties which curing on ambient temperature. The group with 50 % slag content had the highest compressive and flexural strengths, reaching 55.9 MPa and 8.45 MPa at 28 d, respectively. The drying shrinkage of geopolymers increases as the GGBS content goes up. Notably, owing to the evolution of chemical transformation and gel structure, MK exhibits a significant mitigation on shrinkage. Ultimately, with a 50 % slag content, the carbon dioxide emissions of geopolymer can be reduced to 265.36 kg CO2-eq, which is a 43.6 % decrease compared to that of OPC. With a comprehensive consideration of the performance and sustainability potential of geopolymers, it is recommended to introduce GGBS content in the range of 30 %–40 %.

Synergistic effects of mechanochemical activation and selective O-alkylation on the chemical structure and gaseous products evolution during coal flash pyrolysis

Mechanochemical activation offers significant advantages in enhancing the pore structure and active sites of materials, while selective O-alkylation boosts both the homogeneous and heterogeneous reactivity of coal. In this work, mechanochemical activation and selective O-alkylation are synergistically applied to modify pulverized coal. The evolution of the chemical structure was thoroughly characterized using ultimate analysis, Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). Pyrolysis gas chromatography-mass spectrometry (PY-GC-MS) was utilized to investigate the release of crucial gaseous products during the pyrolysis. Additionally, this study focuses on the synergistic effects of mechanochemistry and selective O-alkylation on the chemical structure and pyrolysis characteristics. The results reveal that alkylation boosts the formation of C-O bonds and aliphatic carbon while reducing the presence of aromatic carbon. Moreover, by disrupting intermolecular forces, alkylation induces the fragmentation of expansive aromatic layers into smaller aromatic fragments, thereby generating additional structural defects. Furthermore, the electron transfer process facilitates the conversion of aromatic carbon into aliphatic forms through ring-opening reactions. On the other hand, incorporating alkyl functional groups and initiating ring-opening reactions of aromatic carbons lead to a rise in aliphatic hydrocarbons during the pyrolysis of alkylated coal. However, intensified mechanochemical action hinders the production of aliphatic hydrocarbons. Additionally, during alkylation, the creation of esters and ethers with elevated thermal stability delays the release of oxygen-containing gas products. The findings propose a new pretreatment method for coal utilization, promoting the development of new low-NOx combustion technology.

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal.

The chemical and pore structures of coal play a crucial role in determining the content of free gas in coal reservoirs. This study focuses on investigating the impact of acidification transformation on the micro-physical and chemical structure characteristics of coal samples collected from Wenjiaba No. 1 Mine in Guizhou. The research involves a semi-quantitative analysis of the chemical structure parameters and crystal structure of coal samples before and after acidification using Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments. Additionally, the evolution characteristics of the pore structure are characterized through high-pressure mercury injection (HP-MIP), low-temperature nitrogen adsorption (LT-N2A), and scanning electron microscopy (SEM). The experimental findings reveal that the acid solution modifies the structural features of coal samples, weakening certain vibrational structures and altering the chemical composition. Specifically, the asymmetric vibration structure of aliphatic CH2, the asymmetric vibration of aliphatic CH3, and the symmetric vibration of CH2 are affected. This leads to a decrease in the contents of -OH and -NH functional groups while increasing aromatic structures. The crystal structure of coal samples primarily dissolves transversely after acidification, affecting intergranular spacing and average height. Acid treatment corrodes mineral particles within coal sample cracks, augmenting porosity, average pore diameter, and the ratio of macro-pores to transitional pores. Moreover, acidification increases fracture width and texture, enhancing the connectivity of the fracture structure in coal samples. These findings provide theoretical insights for optimizing coalbed methane (CBM) extraction and gas control strategies.

Impact of Catalysis-Relevant Oxidation and Annealing Treatments on Nanostructured GaRh Alloys.

In this study, we examine the surface-derived electronic and chemical structures of nanostructured GaRh alloys as a model system for supported catalytically active liquid metal solutions (SCALMS), a novel catalyst candidate for dehydrogenation reactions that are important for the petrochemical and hydrogen energy industry. It is reported that under ambient conditions, SCALMS tends to form a gallium oxide shell, which can be removed by an activation treatment at elevated temperatures and hydrogen flow to enhance the catalytic reactivity. We prepared a 7 at. % Rh containing the GaRh sample and interrogated the evolution of the surface chemical and electronic structure by photoelectron spectroscopy (complemented by scanning electron microscopy) upon performing surface oxidation and (activation treatment mimicking) annealing treatments in ultrahigh vacuum conditions. The initially pronounced Rh 4d and Fermi level-derived states in the valence band spectra disappear upon oxidation (due to formation of a GaOx shell) but reemerge upon annealing, especially for temperatures of 600 °C and above, i.e., when the GaOx shell is efficiently being removed and the Ga matrix is expected to be liquid. At the same temperature, new spectroscopic features at both the high and low binding energy sides of the Rh 3d5/2 spectra are observed, which we attribute to new GaRh species with depleted and enriched Rh contents, respectively. A liquefied and GaOx-free surface is also expected for GaRh SCALMS at reaction conditions, and thus the revealed high-temperature properties of the GaRh alloy provide insights about respective catalysts at work.

Investigation on the chemical structure evolution and action mechanism of coal during catalytic combustion

Catalytic combustion is one of the most promising technologies to realize efficient and clean coal combustion, but its catalytic mechanism is unknown until now. This study selected three types coal to explore the influence of catalysts on the chemical structure, surface morphology, and action mechanism during combustion. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were characterized the surface chemical structure of combustion products. The results showed that the aliphatic hydrogen decreased and then increased, the content of –CO and aromaticity(I) increased, and the aromatic condensation (DOC) and CC content decreased by catalysts. Both FTIR and XPS results demonstrated that the catalysts were easy to promote the dehydrogenation condensation reaction between coal molecules, disrupting the stability of coal aromatic structure, thereby generating many free radicals and improving coal combustion. BET and scanning electron microscopy (SEM) were used to observe the effect of catalysts on the pore structure and surface morphology of combustion products. The results showed that the pore structure of product with catalysts continuously formed from micropores to medium pores and even large pores, which accelerated the oxygen transport and chemical reaction on coal surface. Finally, the mechanism of catalytic coal combustion was summarized.

Deformation and kerogen macromolecular structure transformations of the Wufeng–Longmaxi shale under the control of the detachment layer

Tectonism caused strong deformation of the organic-rich shale in the detachment layer of the Wufeng–Longmaxi Formation. In this study, the deformation of the samples collected from the detachment layers were observed using an optical microscope and field emission scanning electron microscopy. Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance, X-ray diffraction, and high-resolution transmission electron microscopy were employed to characterize the macromolecular structure of extracted kerogen samples. The research shows that tectonically deformed shale (TDS) is commonly developed in the detachment layer of the Wufeng–Longmaxi Formation, dominated by brittle–ductile and ductile deformation. In the brittle–ductile deformation stage, the aliphatic carbon (fal) decreases, manifested as the decrease of –CH or –CH2 (falH), from 6.77% to 3.12%. The Al/–OX (defined by FTIR A3000–2800/A1800–1520) gradually decreases, indicating that the brittle–ductile deformation has a stronger effect on the aliphatic structure. The aromaticity I and aromatic carbon (fa) show an increasing trend due to aromatization. In the ductile deformation stage, the fal and aliphatic carbon bonded to oxygen increase first and then decrease, falH decreases gradually, and the aliphatic side chain becomes shorter. The Al/–OX shows an increasing trend, and carbonyl decreases from 7.82% to 5.12%, indicating that the effect of ductile deformation on oxygen-containing functional groups is stronger. The fa shows an overall increasing trend, and the aromatic ring carbon and protonated aromatic carbon increase more significantly due to aromatic condensation. The change trend of the interlayer spacing is opposite in these two stages. However, both brittle–ductile and ductile deformation can improve the size and orientation of aromatic fringes to varying degrees, and the latter is more significant. The rigid mineral intrusion and organic matter (OM) chemical structure evolution are the two main reasons for the low development of OM pores in TDS.

The facilitating effect of sulfide treatment coupled sol-gel method on NH3-SCR activity of Fe–Mn/TiO2 catalysts

The 5Fe–3Mn–S/TiO2-SG catalysts were synthesized by sulfide treatment coupled sol-gel method to develop new NH3-SCR catalysts with wide temperature window, good low-temperature activity and environment-friendly. The evolution of catalyst surface chemical state, morphology, structure, acidity and interaction forces were systematically investigated by XPS, BET, XRD, SEM, H2-TPR, NH3-TPD, UV, IR and steady-state kinetic tests. The influence of sulfide treatment coupled sol-gel method on NO conversion was explored. XRD, BET and SEM characterization revealed that sulfide treatment resulted in smaller catalyst particles and higher dispersion, which increased the specific surface area. XPS, NH3-TPD and steady-state kinetic tests results demonstrated that the sulfide treatment catalysts had a higher surface adsorbed oxygen (Oα) content, which could produce more oxygen vacancies on the catalyst surface, thus increasing the number of acid sites. H2-TPR and UV results demonstrated that the 5Fe–3Mn–S/TiO2-SG catalysts exhibited the strongest contact between the carrier and the active component. The 5Fe–3Mn–S/TiO2-SG catalyst obtained more than 80% NO conversion in the operational temperature range of 220–420 °C, according to the NH3-SCR reaction data. The temperature window was expanded by 120 °C compared to conventional Fe–Mn/TiO2 catalysts, and 98% conversion was achieved at 300 °C. Meanwhile, DFT calculations of the SO42--MnFe2O4(311) crystalline surface of the 5Fe–3Mn–S/TiO2-SG catalysts revealed that it could form stronger chemisorption for both NH3 and NO, which promoted the NH3-SCR reaction more effectively. The DFT calculation results and the experimental findings agreed well.

Effects of Pressurized Pyrolysis on the Chemical and Porous Structure Evolution of Coal Core during Deep Underground Coal Gasification.

During deep underground coal gasification, the semicoke produced by the pyrolysis of dense coal cores is an important material for its gasification and combustion. In this paper, pressurized pyrolysis experiments were carried out on dense coal cores at 700 °C and pressures of 1, 2, and 3 MPa using a shaft furnace. The resulting semicoke and raw coal were analyzed using the characterization methods such as the N2 isothermal adsorption/desorption and scanning electron microscopy, Fourier transform infrared spectrometry (FTIR), and a pressurized thermogravimetric analyzer coupled with a FTIR spectrometer. The pyrolysis gas generation characteristics during pressurized pyrolysis were studied. The mechanisms of evolution of aliphatic functional groups and pore structures in semicoke during pressurized pyrolysis were revealed. The results indicate that the increase in pressure obviously changed the gas composition, most notably, the relative content of CH4 and H2 in the pyrolysis gas. The methane in the pyrolysis gas during pressurized pyrolysis of dense coal cores is mainly from the secondary reaction. As the pyrolysis pressure increased, the ratio of -CH2-/-CH3 became smaller, indicating that the pressure promoted the breakage of the long fat chains. With the increase of the pyrolysis pressure, the surface deformation of pressurized pyrolysis semicoke increases, and the pore structure becomes more abundant.

Mechanistic analysis of chemical structure evolution for coals under igneous intrusion

Thermally altered coals (TACs) have different chemical properties compared to normally buried coals owing to the influence of igneous intrusion. This discrepancy in chemical components of TACs has not been fully revealed, which leads to their underutilization and potential risks in exploitation. Igneous intrusion causes the rearrangement of aromatic rings and the formation of graphite-like features in TACs. Several studies have examined the changes in coal rank and aromaticity during this process but have not explored the overall evolution. In particular, the lateral extension and vertical stacking of aromatic layers in TACs during graphitization are still unknown. To this aim, a range of TACs was collected, from bituminous to semi-graphite. Four experimental analyses were conducted to characterize the chemical structure evolution of TACs, including Raman spectroscopy, Fourier-transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The analysis of the measured parameters indicates that the chemical structure of TACs undergoes evolution as it approaches igneous intrusion. These changes involve an increase in the size of the aromatic structural units, a reduction in structural defects, and an increase in the degree of order. In addition, there is a gradual transition of sp2-sp3 hybridized aromatic rings to sp2 hybridized aromatic rings, resembling the process of graphite formation. The HRTEM micrographs also reveal an enlargement in the size and angular orientation of aromatic fringes. In summary, the evolution of TACs can be categorized into three stages: a) rapid growth of basic structural units (BSU) from bituminous coal to anthracite; b) lateral connections of BSUs from anthracite to meta-anthracite; and c) lateral straightening of BSUs from meta-anthracite to semi-graphite. Understanding this evolutionary mechanism is highly significant in analyzing the formation of pores and in enhancing the utilization and safety of TACs.

Enhancing the Longevity and Functionality of Ti-Ag Dry Electrodes for Remote Biomedical Applications: A Comprehensive Study.

This study aims to evaluate the lifespan of Ti-Ag dry electrodes prepared using flexible polytetrafluoroethylene (PTFE) substrates. Following previous studies, the electrodes were designed to be integrated into wearables for remote electromyography (EMG) monitoring and electrical stimulation (FES) therapy. Four types of Ti-Ag electrodes were prepared by DC magnetron sputtering, using a pure-Ti target doped with a growing number of Ag pellets. After extensive characterization of their chemical composition and (micro)structural evolution, the Ti-Ag electrodes were immersed in an artificial sweat solution (standard ISO-3160-2) at 37 °C with constant stirring. Results revealed that all the Ti-Ag electrodes maintained their integrity and functionality for 24 h. Although there was a notable increase in electrical resistivity beyond this timeframe, the acquisition and transmission of (bio)signals remained viable for electrodes with Ag/Ti ratios below 0.23. However, electrodes with higher Ag content (Ag/Ti = 0.31) became insulators after 7 days of immersion due to excessive Ag release into the sweat solution. This study concludes that higher Ag/Ti atomic ratios result in heightened corrosion processes on the electrode's surface, consequently diminishing their lifespan despite the advantages of incorporating Ag into their composition. This research highlights the critical importance of evaluating electrode longevity, especially in remote biomedical applications like smart wearables, where electrode performance over time is crucial for reliable and sustained monitoring and stimulation.

Petrographic features and carbon structural evolution of a series of high-temperature treated anthracites

Clean energies such as solar, wind, and geothermal power have developed rapidly in recent years and they will probably become the dominant energy source in the future. Thus, coal utilization will have to shift from traditional combustion for energy to coal being a source for raw carbon materials. In this paper, anthracite from the Jinzhushan mine located in central Hunan, China, was treated up to 2900 °C to examine its chemical, petrographic, and carbon structural evolution. Carbon content increased rapidly from 90.2 to 98.8% (daf basis) when treated up to 1700 °C; beyond this temperature the carbon content increased gradually to 100% (daf) at 2900 °C. Altered macerals (vitrinite and inertinite) with an amorphous carbon structure were prevalent in samples treated to ≤1500 °C. Graphitized components were identified in the anthracite heated to ≥1700 °C, as confirmed by micro-Raman spectroscopy and HRTEM. Based on D1 band FWHM versus R1 plots, the carbon structural evolution of anthracite between room temperature and 1700 °C was classified as carbonization, whereas the graphitization process occurred between 1700 and 2900 °C. The nanometric polyaromatic rings retained short-range order during carbonization; the condensed aromatic rings remained randomly oriented at the submicron scale. During graphitization, the aligned structural units were able to undergo condensation reactions and de-wrinkle with temperature increase, leading to a marked increase in crystallite parameters La and Lc. Most vitrinite and inertinite in the anthracite transformed into graphitic components in samples treated to 2600 and 2900 °C, and La showed a significant increase whereas Lc only showed a slight increase between 2600 and 2900 °C. This study will provide insights for optimizing temperature control strategies during preparation of anthracite-based carbon materials in the future.

(Invited) Advanced Organic Electrode Materials for High-Performance and Sustainable Na-Ion Batteries

Na-ion batteries (NIBs) are promising alternatives to Li-ion batteries (LIBs) due to the low cost, abundance, and high sustainability of sodium resources. However, the high performance of inorganic electrode materials in LIBs does not extend to NIBs because of larger ion size of Na+ than Li+ and more complicated electrochemistry. Therefore, it is vital to search for high-performance electrode materials for NIBs. To this end, organic electrode materials (OEMs) with the advantages of high structural tunability and abundant structural diversity show great promise in developing high-performance NIBs. To achieve advanced OEMs for NIBs, a fundamental understanding of the structure–performance correlation is desired for rational structure design and performance optimization. Tailoring molecular structures of OEMs can enhance their performance in Na-ion batteries, however, the substitution rules and the consequent effect on the specific capacity and working potential remain elusive. Herein, we explored the electrochemical performances and reaction mechanisms of various carboxylate-based anode materials, including halogenated sodium carboxylates, N-doped sodium carboxylates, etc. By examining sodium carboxylates with different functional groups, selective N substitution, and extended conjugation structure, we exploited the correlation between structure and performance to establish substitution rules for high-capacity OEMs. Our results show that substitution position and types of functional groups are essential to create active centers for uptake/removal of Na+ and thermodynamically stabilize organic structures. Furthermore, rational host design and electrolytes modulation were performed to extend the cycle life. In addition to sodium carboxylate-based anode materials, we also designed and synthesized novel organic cathode materials based on azo and carbonyl groups for NIBs. The electrochemical performance of the organic cathode materials with an extended conjugated structure such as a naphthalene backbone structure is better than that with benzene and biphenyl structures due to faster kinetics and lower solubility in the electrolyte. It unravels the rational design principle of extending π-conjugation aromatic structures in redox-active polymers to enhance the electrochemical performance. To further optimize the organic cathodes, nitrogen-doped or single layer graphene is employed to increase the conductivity and mitigate the dissolution of organic materials in the electrolytes. The resulting organic cathodes deliver high specific capacity, long cycle life, and fast-charging capability. Post-cycling characterizations were employed to study the chemical structure and morphology evolution upon cycling, demonstrating that the active centers (azo and carbonyl groups) in the organic cathode materials can undergo reversible redox reactions with Na+ for sustainable NIBs. Our work provides a valuable guideline for the design principle of high-capacity and stable OEMs for sustainable energy storage.

Highly selective production of light aromatics from lignin through integrated approach of the torrefaction deoxygenation pretreatment and the dual-catalyst catalytic fast pyrolysis using Nb modified γ-Al2O3 and HZSM-5

Light aromatics are extremely important building blocks for manufacturing of numerous industrial products. The integrated approach of the torrefaction deoxygenation pretreatment (TDP) and the dual-catalyst catalytic fast pyrolysis (DC-CFP) using the HZSM-5 and metal (Nb, Zn, Ga, Ni, Ce) modified γ-Al2O3 as catalyst was employed to enhance the production of light armatics from the hardwood lignin. The torrefaction deoxygenation mechanism was established based on the evolution of chemical structure of lignin. The maximum removal rate of oxygen element was 22.82%, achieved at the TDP temperature of 300 °C. The oxygen element was removed through the cleavage of β–O–4 bond, the aliphatic–OH and aliphatic–HC═O on the side-chain, and the aromatic–OH and aromatic–OCH3 on the aromatic nucleus, releasing as the oxygenated gaseous compounds (CO2, H2O, and CO). The synergistic effect between HZSM-5 and metal modified γ-Al2O3 in DC-CFP was observed, remarkably improving the yield of light aromatics. Metal modified γ-Al2O3 aimed to first convert lignin into macromolecular phenols, and HZSM-5 was complementary used to convert the macromolecular phenols into light aromatics by the deoxygenation reactions. The maximum selective yield of bio-BTX were 74.39%, obtained at TDP temperature of 250 °C, lignin-to-catalyst ratio of 1:3, and HZSM-5-to-15%Nb/Al2O3 of 2:2.

Study on the structural evolution and heat transfer performance of Cu supported on regular morphology CeO2 in CO catalytic combustion and chemical looping combustion

Chemical looping combustion (CLC) and catalytic combustion (CC), which are potential technologies to promote CO→CO2 efficient conversion and energy conservation for the steelmaking off-gas, are investigated in reaction activity, structure evolution catalysts/oxygen carriers (OCs) and energy recovery using Cu/CeO2 materials. Activity results suggest that the rod-shaped samples with well-defined (100) crystal faces exhibit higher activity than the sphere-shaped samples with (111) crystal faces, obtaining the optimized copper content of 3 wt%. IR spectra confirmed the proposed reaction pathway that the CO adsorbed on copper sites (Cu+–CO) at the Cu–Ce interface reacts with adjacent surface lattice oxygen. The gaseous oxygen continuously migrates to the external surface of materials, thus resulting in strongly exothermic CO self-sustained combustion during CC. Such a violent reaction does not cause obvious evolution of chemical composition, crystalline phase and structure. Since the active lattice oxygen is gradually consumed but not replenished by external gaseous O2 in time, CO combustion is not self-sustained during CLC. Therefore, the reduction cycle is no longer confined to the surface of the material but penetrates deep into its body, which accelerates Cu+ enrichment at the surface and leads to irreversible sintering and agglomeration of the material.

Gas-pressurized torrefaction of lignocellulosic solid wastes: Low-temperature deoxygenation and chemical structure evolution mechanisms

A novel gas-pressurized (GP) torrefaction realizes deeper deoxygenation of lignocellulosic solid wastes (LSW) to as high as 79% compared to traditional torrefaction (AP) with the oxygen removal of 40% at the same temperature. However, the deoxygenation and chemical structure evolution mechanisms of LSW during GP torrefaction are currently unclear. In this work, the reaction process and mechanism of GP torrefaction were studied through follow-up analysis of the three-phase products. Results demonstrate gas pressure causes over 90.4% of cellulose decomposition and the conversion of volatile matter to fixed carbon through secondary polymerization reactions. Above phenomena are completely absent during AP torrefaction. A deoxygenation and structure evolution mechanism model is developed through analysis of fingerprint molecule and C structure. This model not only provides theoretical guidance for optimization of the GP torrefaction, but also contributes to the mechanism understanding of pressurized thermal conversion processes of solid fuel, such as coal and biomass.

Effects of aging degradation and reactive reconstruction on the structure and properties of styrene–butadiene–styrene block copolymer

Achieving high-performance recycling of aged SBS modified asphalt will help promote the sustainable development of transportation infrastructure. The destruction of the SBS cross-linking network is an important reason for the deterioration of the performance of aged SBS modified asphalt. Scientific reconstruction of aged SBS cross-linked network is the key to achieving the performance recovery of aged modified asphalt. In this research, the evolution of chemical structure, molecular weight, thermodynamic properties, multiple stress creep recovery capability and rheological property of SBS during the process of aging degradation and reactive reconstruction were systematically investigated. The results showed that the molecular weight and creep recovery capability of SBS decreased sharply, and its complex modulus and phase angle exhibited a strong temperature and frequency dependence after aging. While the number average molecular weight of aged SBS increased by over 70% after reactive reconstruction, and its thermal-oxygen stability shown better performance as compared with that of fresh SBS. Meanwhile, the glass transition temperature of aged SBS was restored to −43.8℃ and −54.9℃ after reactive reconstructed by toluene diisocyanate (TDI) and isocyanate pre-polymer. Therefore, isocyanate pre-polymer with flexible long chain structure was more benefit for improving the low-temperature performance of reactive reconstructed aged SBS. Furthermore, the creep recovery ability and complex modulus of aged SBS were all significantly improved, and exhibited dramatically high-elastic properties after reactive reconstruction. And as compared with isocyanate pre-polymer, TDI with benzene ring rigid structure was more conducive to restoring the medium–high temperature rheological properties of aged SBS. Therefore, effective restoration of molecular weight and performance of aged SBS can be achieved by using reaction reconstruction method. This study would provide inspiration and ideas for the high-value recycling of waste polymer modified asphalt.

Biomimetic and flexible high-performance carbon paper prepared by welding three-dimensional carbon fiber network with polyphenylene sulfide spherical sites for fuel cell gas diffusion layer

High-performance carbon fiber paper (CFP) is usually an important part of the fuel cell gas diffusion layer (GDL). However, the preparation of CFP for GDL is still a challenge due to its arduous preparation process. Here, inspired by the structure of bird's nest in nature, we present the original design of PPS spherical sites welding three-dimensional (3D) carbon fiber network to produce high-performance CFP by facile wet papermaking and heat treatment. With a 3D CF network as the skeleton and PPS spherical sites as the welding points, CFs/PPS composite paper exhibits good mechanical strength and outstanding flexibility. Meanwhile, the excellent conductivity (6.8 S/cm) is integrated with super-hydrophobic performance, electrothermal performance (Tmax = 365 °C), heat resistance (DTGmax>575 °C), and corrosion resistance, becoming a high-performance multifunctional CFP. The mythical combination of these properties makes CFs/PPS composite paper an ideal candidate in the field of fuel cell GDL. In addition, the evolution of chemical structure of CF/PPS during carbonization is emphasized, which is of great significance for the properties of composite paper. This work presents a leap forward in the preparation of multi-property high-performance CFP in a simple method and is a key step toward exploring how the structural changes of CFs/PPS composite paper can be understood during carbonization.

Scanning transmission X-ray microscopy of hydrogen evolution electrocatalysts on reduction graphene oxide membranes

Cobalt is one of the promising metal catalysts for hydrogen evolution reaction, and its catalytic performance can be further improved by supporting on graphene oxide and reduced graphene oxide as an active interface to the substrate. Scanning transmission X-ray microscopy (STXM) identifies the position-dependent functional groups on the membranes and chemical structure evolution of the CoxOy. The in-situ mass spectrometer analysis shows the reduction current and H2 generation of the electrocatalyst enhanced by the addition of graphene oxide and reduced graphene oxide to CoxOy, as compared to the CoxOy on the bare substrate. The best hydrogen evolution reaction performance of CoxOy at − 2.5 V is correlated with the high Co3+ concentration existed on the reduced graphene oxide, as evidenced by the nano- and element-resolved capability of STXM. With the economical electro-reduction synthesis, this study provides brand-new insights into the critical role of substrate rGO and electrocatalyst CoxOy toward the design of high efficiency electrocatalyst.

Insights into the chemical structure evolution and carbonisation mechanism of biomass during hydrothermal treatment

The thermochemical conversion of biomass energy contributes to the goals of carbon peaking and carbon neutrality. In this paper, the evolution of the chemical structure of corn stalk (CS) during hydrothermal carbonisation (HTC) was investigated and the effect of temperature on the physicochemical properties, carbon skeletal structure, and surface functional groups of the obtained hydrochar was explored. The results indicate that the H/C and O/C atomic ratios of the hydrochar decreased as the HTC temperature increased. The -C-(O, N), –C=O, and O–C=O bonds in the CS rapidly formed aromatic structures through cyclisation, condensation, or polymerisation, which in turn increased the -C-(C, H)/C=C content in the hydrochar. The oxygen-containing functional groups in the CS and hydrochar were mainly carbonyl (C=O), aromatic ring (C=C), ether oxygen bond (C–O), alcohol-phenol oxygen bond (C–OH), and carboxyl (O=C–O) groups. A high HTC temperature lowered the degree of substitution of the aromatic hydrocarbons and increased their degree of condensation. The hydrolysis stage and the formation of aromatic structures were competing processes. At low temperatures, the hydrolysis reaction was dominant and the generation of aromatic structures was secondary. However, at high temperatures, the intermediate compounds underwent transformation after hydrolysis, and the generation of aromatic structures was more competitive.

Insight into the ammonia torrefaction and pyrolysis system of cellulose: Unraveling the evolution of chemical structure and nitrogen migration mechanism

Insight into the ammonia torrefaction and pyrolysis system of cellulose: Unraveling the evolution of chemical structure and nitrogen migration mechanism