Cement industry continues to face significant environmental challenges due to its substantial CO₂ emissions, primarily stemming from carbonate decomposition in raw materials and fossil fuel combustion during production. Carbonatable binders and carbonation curing technologies have a promising potential for CO₂ reduction in cement production, and the existing methods involve the calcination of calcareous and siliceous raw materials to produce low-lime silicates for their emission reduction limits. Natural wollastonite, primarily composed of calcium silicate (CS), has an attractive alternative due to its abundant reserves and ease of extraction. Utilizing natural wollastonite as a carbonatable binder can eliminate both fossil fuel combustion and the need for calcareous raw materials, thereby avoiding the carbonate decomposition entirely. However, its application is currently limited due to its low carbonation reactivity. This study was to investigate the enhancement of carbonation reactivity of natural wollastonite via optimizing calcination activation to develop a high-performance carbonatable binder.

Natural wollastonite was calcinated under various calcination activation condictions (i.e., temperature, time, and cooling regimes). The activated wollastonite powder was mixed with water and compressed at 4 MPa to form the samples with different two dimensions (i.e., 20 mm × 20 mm × 20 mm and 20 mm × 80 mm × 20 mm). These samples underwent carbonation curing for 24 h before characterization. The mechanical properties were evaluated through compressive and flexural strength tests. The phase composition was characterized by X-ray diffraction (XRD) on both the wollastonite powder and carbonated samples before and after calcination activation. The structure of the samples was determined by Fourier-transform infrared spectroscopy (FT-IR) to analyze both the calcination activation effects and the resulting carbonation products. The microstructural evolution was determined by scanning electron microscopy (SEM). CO₂ uptakes were analyzed by thermogravimetric analysis (TGA).

This study reveals that calcination activation significantly enhances the carbonation hardening performance of natural wollastonite via increasing carbonation reactivity. Optimal conditions are identified at a calcination temperature of 1200 ℃, effectively transforming Para-CS and β-CS into metastable α-CS. The effective calcination time for the complete transformation is 60 min, while preserving the material valuable fibrous structure. Water quenching is found to be the most effective cooling method, retaining higher concentrations of crystal defects in the metastable α-CS. The transformation from a chain structure to a ternary ring structure at 1200 ℃ results in an increased structural distortion, thus leading to an enhanced carbonation reactivity of α-CS. The carbonation analysis reveals the extensive formation of carbonation products, primarily calcium carbonate and highly polymerized silica gel, resulting in a dense microstructure. Note that the preservation of the fibrous structure through calcination activation allows unreacted wollastonite to serve as a fibrous reinforcement within the carbonation hardening system, contributing to enhanced mechanical properties.

The results showed that calcination temperature exhibited a dominant effect, followed by calcination time and cooling regime. The optimal calcination temperature of 1200 ℃ led to the improvements in compressive strength, flexural strength, and CO₂ uptakes of the carbonated samples. The calcination time was critical in ensuring a complete phase transformation, while maintaining structural integrity, and a rapid cooling could preserve crystal defects that enhanced carbonation reactivity. The resulting carbonatable binder developed a carbonation hardening system comprising calcium carbonate, highly polymerized silica gel, and unreacted wollastonite fibers that could serve as an effective reinforcement within the carbonation hardening system. These findings could provide a promising pathway for the large-scale utilization of natural wollastonite in sustainable construction materials, having a potential for reducing the environmental impact of cement industry.

Thermal barrier coatings (TBCs), primarily composed of yttria-stabilized zirconia (YSZ), are critical materials for protecting the hot section components of gas turbine engines due to their high fracture toughness, melting point, and thermal stability. However, increasing operational temperatures has some challenges, particularly from molten CMAS (CaO-MgO-Al₂O₃-SiO₂) deposits that can penetrate TBCs, reduce their strain tolerance, and accelerate failure. The performance of YSZ deteriorates upon interaction with CMAS, leading to phase transformation and coating detachment. Research efforts focus on modifying YSZ with TiO₂, Cr₂O₃, or Al₂O₃ based on sacrificial protection strategies, enhancing resistance to CMAS via promoting the crystallization of compounds such as gehlenite (CaAl₂Si₂O₈). This study was to investigate the effect of Ti on the reactivity of sacrificial protective Al₂O₃ coatings with CMAS. Al and Ti layers were deposited on YSZ by magnetron sputtering and heat treatment to form mixed oxide layers to improve the protective efficacy against CMAS attack.

In this study, graphite was utilized as a substrate for YSZ coatings. After degreasing and cleaning, graphite substrates were roughened with alumina sand (WA22). A YSZ powder (KF231) was sprayed onto the substrates in Ar-H₂ as a plasma gasby a model Multicoat APS system (Oerlikon Metco Co., Switzerland) to deposit a YSZ coating with the thickness of 1500 μm. The graphite substrate was removed by heat treatment at 750 ℃ for 3 h. Subsequently, Al and Ti films were deposited on the YSZ surface via magnetron sputtering, and followed via annealing at 1000 ℃ for 2 h to form TiO₂-Al₂O₃ modified YSZ (TA-YSZ) coatings. An additional control group of Al₂O₃-modified YSZ (A-YSZ) without Ti deposition was also prepared.

CMAS powders with a composition of 33%CaO-9%MgO-13%AlO_1.5-45%SiO₂ (in mole fraction) were synthesized via melt quenching. The melting and crystallization temperatures of CMAS and its mixtures with Al₂O₃ and TiO₂ were characterized by differential scanning calorimetry (DSC). The thermal corrosion test was performed by painting the coated surface with a CMAS slurry and exposing it to 1300 ℃ for 5 min or 1250 ℃ for 2 h and 10 h (after 2 h heat treatment, the temperature was lowered in a furnace and then raised to 1250 ℃ for 2 h, and this was repeated for 5 times). The phase structure was determined by X-ray diffraction (XRD, Rigaku Smart Lab., Japan). The surface and cross-sectional microstructures of the corroded samples were analyzed by a model Phenom ProX field emission scanning electron microscope (SEM, Thermo Scientific, Netherlands) equipped with an energy-dispersive X-ray spectroscopy (EDS) system. The corroded samples were embedded in epoxy resin, cut and diamond-polished before performing the SEM analysis of the coating cross-section. The phase structure of YSZ was determined by a model InVia-Reflex Fourier-transform Raman spectroscopy (Renishaw Co., UK).

Al and Ti films are sequentially deposited on the surface of YSZ coatings via magnetron sputtering. Al film exhibits a typical physical deposition structure. After heat treatment, the Ti element shows a dotted band above Al layer and forms an oxide layer. The results of DSC analysis reveal that the crystallization and melting characteristic temperatures of the three powder samples (i.e., CMAS, CMAS+Al₂O₃, and CMAS+Al₂O₃+TiO₂) shift towards lower temperatures in such an order. This indicates that the addition of Al₂O₃ and TiO₂ effectively reduces the crystallization temperature of CMAS and affects its melting characteristics.

TA-YSZ and A-YSZ coatings coated with CMAS and subjected to treatments at 1300 ℃ for 5 min or 1250 ℃ for up to 2 h and 10 h show that Ti promotes reactions between CMAS and Al₂O₃ to form high-melting-point crystalline phases such as gehlenite (CaAl₂Si₂O₈) and spinel (MgAl₂O₄). The introduction of Ti significantly enhances the interfacial reaction kinetics between the coating and the CMAS melt. Ti facilitates the formation of high-melting-point crystalline phases. Also Ti accelerates the crystallization process of corrosion products, forming a dense reaction barrier layer that effectively consumes molten CMAS and inhibits its penetration into the YSZ substrate. Moreover, the time and spatial distribution characteristics of the reaction products can occur during corrosion testing due to the different reaction kinetics characteristics of high-melting-point crystalline phases. Under the sacrificial protection mechanism of the surface coating, no phase transformation appears in the YSZ substrate.

YSZ coatings prepared by the atmospheric plasma spraying method were subjected to magnetron sputtering to deposit Al and TiAl films on their surface, which were then in-situ oxidized to form Al₂O₃ and TiO₂-Al₂O₃ (TA-YSZ) layers. The synergistic effect of Ti and Al on the enhancement of the CMAS corrosion resistance of YSZ coatings was investigated. The results showed that Ti significantly accelerated the reaction between CMAS and Al₂O₃, leading to the formation of high-melting-point products such as gehlenite and spinel, and promoted the crystallization of corrosion products. These actions effectively hindered the penetration of molten CMAS into the YSZ coating interior.

A photocatalytic material of Ag₁₀Si₄O₁₃ is widely concerned due to its band structure suitable for visible light response and built-in electric field promoting photogenerated carrier separation. However, in the photocatalysis process, Ag₊ in Ag₁₀Si₄O₁₃ is easily reduced by photoelectrons and accumulates Ag elements, affecting the cycle stability of the photocatalytic system. Graphene oxide can effectively transfer photogenerated electrons, and amorphous SiO₂ can inhibit ion diffusion leaching, which are expected to slow down the photoreduction of Ag₁₀Si₄O₁₃. In this paper, x% SiO₂/Ag₁₀Si₄O₁₃/GO (SAG) composites with different amounts of amorphous SiO₂ were prepared via adding graphene oxide (GO) and silica sol in the process of Ag₁₀Si₄O₁₃ preparation by a sol-gel method. The effect of amorphous SiO₂ addition on the crystal structure, morphology and photoelectrochemical properties was investigated. Methylene blue (MB) was used as a target. The results show that a small amount of amorphous SiO₂ can greatly improve the photoreduction resistance of Ag₁₀Si₄O₁₃ photocatalysts, and broaden the photoresponse range and increase the adsorption capacity of the material for MB. However, the addition of amorphous SiO₂ can simultaneously reduce the migration rate of photogenerated carriers and accelerate the recombination of photogenerated electron-hole pairs. Therefore, the photocatalytic degradation efficiency of the composite system firstly increases and then decreases with the increase of SiO₂ addition. The degradation rate of SiO₂/Ag₁₀Si₄O₁₃/GO (SAG-1) samples can reach 99% under visible light for 40 min, showing a good cyclic stability. After 5 cycles, the crystal structure of the materials becomes stable and the degradation rate can still reach 97%.

In pre-hydrolysis of ethyl orthosilicate: 0.47 g of citric acid was added to 26 mL of anhydrous ethanol under magnetic stirring until complete dissolution, and then 5 mL of ethyl orthosilicate and 1.65 mL of distilled water were added in dropwise to the solution and the solution was stirred for 1 h and sealed for 1 week aging to obtain the silica sol. In preparation of Ag₁₀Si₄O₁₃/GO, 2.1 mL of silica sol and GO sol containing 1%(in mass) Ag₁₀Si₄O₁₃ were added to 10 mL of distilled water under ultrasound and magnetic stirring. 1.6 mL of 0.38 g/mL AgNO₃ solution was added in dropwise to the mixed solution above under stirring for 1 h and aging for 24 h to obtain the precursor sol. The precursor sol was dried, ground and heat-treated at 400 ℃ for 5 h to obtain a brick-red Ag₁₀Si₄O₁₃/GO powder=(i.e., AG). In preparation of SiO₂/Ag₁₀Si₄O₁₃/GO, x%(in mass) Ag₁₀Si₄O₁₃ (x=1, 2, 3, 4) of silica sol was added, stirred continuously for 1 h and aged for 24 h to obtain x% SiO₂/Ag₁₀Si₄O₁₃/GO precursor sol. The subsequent steps were the same as for AG to obtain x% SiO₂/Ag₁₀Si₄O₁₃/GO powders (i.e., SAG-1, SAG-2, SAG-3, and SAG-4), respectively.

The crystal structure of the materials was characterized by a model D8/axs X-ray diffractometer (XRD, Bruker Co., Germany). The microscopic morphology of the materials was observed by a model JSM-6701F transmission electron microscope (TEM, Electro-Optics Co., Japan). The chemical state was analyzed by a model PHI5702 X-ray photoelectron spectrometer (XPS, Physical Electronics Inc., USA). The photoresponsive properties were determined by a model U-3900H diffuse reflectance spectrometer (UV-Vis, Hitachi High-Technologies Co., Japan). The fluorescence emission spectra of the materials were determined by a model F97 fluorescence spectrophotometer (FSP, Shanghai Prismatic Technology Co., Ltd., China). The impedance, transient photocurrent, and Mott-Schottky curves were determined by a model CHI660D electrochemical workstation (Shanghai Tatsuwa Instrumentation Co., Ltd., China).

The sample of 0.1 g was weighed and stirred in 100 mL of 20 mg/L MB solution, which was protected from light. For every 10 min, 3 mL of the sample was removed and the supernatant was centrifuged to determine the concentration of MB by a UV spectrophotometer. The adsorption performance was evaluated by a ratio of the concentration of the solution after adsorption, c_t, to the initial concentration of MB, c₀, at time t (c_t/c₀). After dark adsorption equilibrium, a 300 W xenon lamp was used as a light source, a filter (λ>420 nm) was added to simulate visible light, the distance from the light source to the liquid surface was fixed at 15 cm, the sample of 3 mL was taken for every 5 min, and the supernatant was centrifuged to determine the concentration of MB by a UV spectrophotometer. The photocatalytic performance was evaluated by a ratio of the concentration of the degraded solution to the initial concentration of MB, c₀, at the time of t′ (c_t/c₀).

Five cycling experiments were performed on AG and SAG-1 to evaluate the stability of the photocatalytic properties of the materials. The stability of the crystal structure of the materials was evaluated based on the XRD patterns after each cycle.

The XRD patterns show that the introduction of SiO₂ has no effect on the crystal structure of Ag₁₀Si₄O₁₃. The TEM images of SAG-1 indicate the presence of graphene oxide, Ag₁₀Si₄O₁₃ and SiO₂. The UV-Vis diffuse reflectance spectra show that the edge of the absorption band of SAG-1 extended to 660 nm, which can be caused by the defects formed during the preparation of the material, but the forbidden bandwidth changes slightly, indicating that the protective layer of SiO₂ does not cause any significant changes in the band gap. The PL spectra show that the fluorescence intensity of the material increases gradually with the increase in the content of amorphous SiO₂, showing that the photogenerated carrier complexation rate increases with the increase of SiO₂ incorporation. The photocatalytic performance of Ag₁₀Si₄O₁₃ decreases significantly from 99% to about 90% after 5 cycles, while the photocatalytic performance of SAG-1 does not change after 5 cycles and still reaches 97%. The results show that the introduction of a small amount of SiO₂ can slow down the reduction production of Ag⁺ during the photocatalytic degradation of Ag₁₀Si₄O₁₃, and the crystal structure remains stable after some cycles, which greatly improves the stability of the material structure.

SiO₂/Ag₁₀Si₄O₁₃/GO ternary composites with different SiO₂ composite amounts were synthesized by a sol-gel method with GO and excess silica sol in an one-pot method. The complexing agent citric acid was used as a "bridge" to allow Ag₁₀Si₄O₁₃ nanoparticles to grow uniformly on GO, and the excess silica sol was attached to the precursor surface, forming an amorphous SiO₂ protective layer after heat treatment. The introduction of the amorphous SiO₂ protective layer did not affect the crystal structure of Ag₁₀Si₄O₁₃, which could extend the visible-light response range of the composite photocatalyst and significantly improve the adsorption performance for cationic dyes. However, SiO₂ could reduce the migration rate of photogenerated carriers and accelerate the assembly of photogenerated electron-hole pairs, affecting the photocatalytic performance of the material. An appropriate amount of amorphous SiO₂ protective layer could improve the photoreduction resistance and cycling stability of Ag₁₀Si₄O₁₃ photocatalysts, while maintaining the original photocatalytic activity. The degradation rate of the SAG-1 sample was still 97% after 5 cycles, and the crystal structure remained stable after 5 cycles (I₍₁₃₂₎/I₍₁₁₁₎ =1.16). This work could provide an reference for solving the problem that the materials of Ag-based efficient photocatalysts could be susceptible to photocorrosion during the photocatalytic process.

TEC technology offers precise temperature control, addressing challenges like localized hotspots and complex heat flows in high-power-density chips, which is a key technology for sustainable and high-efficiency thermal management. However, the existing researches still face significant challenges in achieving the ultra-thin designs and high-efficiency required for modern chip architectures. The ability to manage transient high heat flux while maintaining scalability and cost-efficiency remains a concern. Future efforts should focus on the balance of cost, durability, and TE properties of materials through nanoengineering, doping, and interface engineering to enhance their performance. In terms of device design, optimizing multi-stage architectures and achieving miniaturization alongside intelligent functionalities will enable more efficient heat dissipation. These improvements are indispensable for catering to the increasing demands of high-power chips. At the system level, the integration of TEC with liquid cooling or heat pipes will enhance overall thermal management efficiently. The incorporation of TE generation provides new opportunities for constructing sustainable and energy-efficient cooling systems. With continued innovation in materials preparation, device design, and system integration, TEC may pave a way for efficient, reliable, and scalable solutions for the next generation of electronic systems.

Although flexible thermoelectric technology has made remarkable progress in waste heat power generation, wearable devices and smart textiles, having a great application potential, there are still a series of problems in practical application. Therefore, a more systematic and comprehensive study is needed. The output of flexible substrate thermoelectric devices depends on the heat harvesting area and temperature gradient, and can produce power densities ranging from a few microwatts per square centimeter to a few milliwatts per square centimeter. However, the interface thermal resistance of low-dimensional flexible devices will lead to a low conversion efficiency, and its preparation technology is still limited to a large-scale application. Major challenges for fiber thermoelectric devices include building larger temperature gradients in the direction of heat flow, designing scalable architectures, improving mechanical stability, and enhancing comfort. In addition, the development of advanced preparation technologies such as magnetron sputtering and pulsed laser deposition will also achieve a large-scale production. Also, the combination of boost and energy storage technologies, such as efficient DC-DC converters and new energy storage systems, will effectively solve the problem of low output voltage of thermoelectric devices, so that they can directly drive low-power sensors or communication modules. Finally, with the further development of interface stability and flexible design of flexible substrate thermoelectric devices, flexible thermoelectric devices will be more widely used in wearable technology, smart textiles and some related fields.

RAMBs are regarded as one of the most promising alternatives to the existing battery technologies for large-scale energy storage due to their low cost, high capacity, superior safety, and abundant availability of aluminum. However, RAMBs still encounter significant challenges, with the lack of highly reversible, long-lifetime Al anodes being a critical bottleneck. Although considerable progress has been made in this field, it remains in its early stages and requires further comprehensive investigation. A future research can focus on the following aspects, 1) Revealing the in-depth failure mechanisms and enhancing the stability of Al metal anodes. Whether through anode modification or electrolyte optimization, the underlying mechanisms must be thoroughly investigated, with particular attention to the failure processes and stability of the anode interface. In-situ characterization techniques are highly preferred to identify the fundamental causes of interface failure. Also, there is a need to refine some methods for evaluating anode stability and to establish standardized performance parameters and evaluation criteria. 2) Exploring high-performance, non-corrosive, and cost-effective RAMBs systems. The performance of RAMBs is highly depended on the properties of the electrolyte and its compatibility with Al anodes. To address the corrosion challenges posed by chloride-based ILs on both Al and other metallic parts, the design of non-corrosive electrolytes is essential for practical applications. However, employing such non-corrosive electrolytes necessitates overcoming an issue of natural Al₂O₃ passivation layer on Al anode. 3) Developing high-capacity and stable cathode materials. The extremely high charge density of Al³⁺ results in an intense Coulomb interaction with intercalation-type cathode materials, which slows down the intercalation/deintercalation kinetics of Al³⁺ and leads to an irreversible structural damage to the cathode. For conventional conversion-type cathodes, their intense bonding with Al³⁺ severely limits the reversibility of redox reactions. It is thus critical for advancing RAMBs to develop novel cathode materials that can efficiently utilize the three-electron-transfer mechanism of Al³⁺ and exhibit fast kinetics.

In this review, we emphasize the critical importance of the fundamental failure mechanisms of Al anodes and clarify Al³⁺ solvation and de-solvation behaviors and breakthroughs in the design of pivotal materials such as non-corrosive and high-performance electrolytes and high-capacity cathodes. This review provides valuable insights for the development of next-generation RAMBs and contributes to accelerating their practical application.

Composite solid electrolytes (CSE), which consist of a polymer matrix combined with inorganic fillers, leverage the advantages of both solid polymer electrolytes (SPE) and inorganic solid electrolytes, offering promising prospects for practical applications. However, the development and implementation of CSE are still in their early stages, revealing a significant gap between their existing performance and application requirements, necessitating further enhancements. To address this, CSE with specific morphologies and microstructures must be designed to improve the connectivity of ion migration channels, facilitating efficient ion transport. An effective interfacial conductive network can be established via carefully controlling the ratio, size, dispersion, and other characteristics of the inorganic fillers, significantly enhancing ionic conductivity. The strategic application of simulation and characterization techniques to elucidate the ion transport mechanisms within CSE is crucial for advancing the performance of these materials. Lastly, to lower the costs associated with ASSB, the fabrication process of CSE should be streamlined to be simple, time-efficient, and material-saving, while also being compatible with the existing battery production lines to enhance the practicality.

The development of fluorescence intensity-based thermometry faces two major challenges, i.e., enhancement of temperature measurement performance and expansion of application domains. Regarding performance improvement, the existing fluorescence intensity thermometric methods primarily focus on fluorescence intensity ratio (FIR) techniques involving thermally coupled and non-thermally coupled energy levels. However, several critical issues have emerged.

Firstly, rare-earth ions and certain transition metal ions exhibit significant thermal quenching effects at elevated temperatures, thus leading to substantial attenuation of fluorescence signals in high-temperature environments. Secondly, in thermally coupled energy level-based FIR thermometry, despite the abundant energy levels of rare-earth ions, some studies on potential thermally coupled energy levels for specific rare-earth ions remain insufficient. Moreover, systematic investigations into performance variations among different thermally coupled energy level pairs for FIR thermometry are notably lack. Thirdly, the fundamental mechanisms underlying non-thermally coupled FIR thermometry, particularly the operational principles of dual-luminescent-center systems, have yet to establish universally accepted theoretical explanations. The energy transfer processes and interaction mechanisms between different luminescent centers' energy levels require a further elucidation. In terms of luminescent center selection, more combinations such as rare-earth-rare-earth ion pairs and rare-earth-transition metal ion systems warrant a comprehensive exploration. Lastly, although numerous temperature-sensitive materials demonstrate either high upper measurement limits or superior relative sensitivity, materials simultaneously with a high relative sensitivity in a broad temperature range remain scarce. Therefore, the design and development of novel temperature-sensitive materials will constitute a crucial research frontier.

Concerning application expansion, fluorescence intensity thermometry has attracted considerable attention due to its unique characteristics. The existing thermometric materials exhibit diverse advantages, each possesses inherent limitations. A critical challenge lies in rationally designing application scenarios based on material properties to maximize their functional advantages for practical implementations. Current research predominantly focuses on material development itself, with insufficient exploration of potential application fields. Note that raw materials cannot be directly employed in industrial production but require integration into temperature sensor architectures coupled with complete testing systems. However, the research framework spanning from material development to practical applications, encompassing complete testing systems and material optimization, remains underdeveloped. Furthermore, although applications have extended to biomedical and aerospace fields, investigations under extreme conditions such as ultra-low temperatures and highly corrosive environments remain inadequate.

It is anticipated that these challenges above will be progressively addressed with sustained research efforts. The development of advanced temperature-sensitive materials with enhanced performance and their subsequent integration into industrial applications are expected to drive significant advancements in fluorescence intensity-based thermometry technology.

Room-temperature sodium-sulfur (RT Na-S) batteries, as one of effective candidates for next-generation high-energy-density battery systems, have the advantages of high theoretical energy density (i.e., 1274 W·h·kg^-1), high elemental abundance (i.e., S and Na) and low cost. However, the practical application of RT Na-S batteries is restricted due to the poor electronic conductivity of sulfur, sluggish reaction kinetics, and sodium polysulfides (NaPSs) shuttle effect. The related studies are performed on cathode materials of RT Na-S batteries. Among various materials, two-dimensional layered materials have attracted extensive attention due to their unique structures and physicochemical properties, showing a substantial promise for applications. Compared to conventional experimental research methods, first-principles computational techniques can assist in designing novel high-performance electrode materials in atomic and electronic scales. This paper was thus to investigate g-C₃N₄ as a catalyst for RT Na-S batteries based on the first-principles calculation methods. In addition, the chemical interactions between g-C₃N₄ and NaPSs, electronic structure, and reaction energy barriers were also analyzed.

Density functional theory (DFT) calculations were carried out by a software named Vienna ab initio simulation package (VASP). The exchange-correlation energy was described using the Perdew-Burke-Ernzerhof (PBE) functional within the framework of the generalized gradient approximation (GGA). A plane-wave cutoff energy of 500 eV was chosen. A vacuum layer larger than 20Å was used in the calculations to avoid the interlayer interactions. The convergence of energy and force criteria on the atoms were set to be 10^-5 eV and 0.02 eV·Å^-1, respectively. The DFT-D3 method was used to calculate the long-range van der Waals interactions. The 3×3×1 and 4×4×1 Monkhorst-Pack K-points were set in the first Brillouin zone for geometric optimization and calculation of density of states (DOS), respectively. The adsorption energy of NaPSs adsorbed on g-C₃N₄ monolayer was calculated by

The g-C₃N₄ studied belongs to a hexagonal crystal system, where C and N atoms are bonded in sp² hybridized configuration, forming a conjugated π-electron structure. The density of states (DOS) of g-C₃N₄ monolayer shows semiconductor characteristics with a band gap of 1.12 eV. The adsorption energy is a fundamental criterion for assessing whether a material can anchor polysulfides. The adsorption energies of NaPSs and S₈ on the g-C₃N₄ surface were calculated, and all the values range from -1.0 eV to -5.0 eV, indicating that g-C₃N₄ can be ideal candidates for anchoring NaPSs. The analysis of DOS and differential charge density of these adsorption systems shows that electron transfer occurs through Na-S and Na-N bonds and the band gap decreases, compared to the pristine g-C₃N₄ (except S₈ adsorption system), facilitating electron transfer and providing electrons for the redox processes of NaPSs. The Gibbs free energy calculation for the entire discharge process reveals that the energy barrier of the rate-determining step is only 0.70 eV. These results emphasize a pivotal role played by the g-C₃N₄ in accelerating the conversion of NaPSs.

Based on first-principles calculations, we systematically investigated the anchoring and catalytic behavior of g-C₃N₄ toward NaPSs. The results showed that g-C₃N₄ could have a great potential as a sulfur host and catalytic material for RT Na-S batteries. g-C₃N₄ had an anchoring effect on NaPSs, contributing to improved battery cycle life. g-C₃N₄ could effectively capture NaPSs from the electrolytes, suppressing the shuttle effect. And g-C₃N₄ accelerated the conversion kinetics of NaPSs, enhancing sulfur utilization. All these findings could underscore an immense potential of g-C₃N₄ in the design of RT Na-S battery cathodes.

Porous silicon-based anode materials with their high theoretical specific capacity (i.e., approximately 4200 mA·h·g^-1) and unique porous structure have a promising application potential in the field of lithium-ion batteries. Their porous structure provides effective buffering space for the significant volume change (i.e., 300%) of silicon during charging and discharging, effectively mitigating material pulverization and maintaining the integrity of the electrode structure, thereby enhancing battery cycle stability and Coulombic efficiency, and greatly increases the utilization rate and conductivity of active materials, thus enhancing the energy density of lithium-ion batteries. However, despite the enormous application prospects of porous silicon-based anode materials, their high preparation costs, low initial Coulombic efficiency, and capacity fade after long-term cycling remain some critical factors restricting their commercialization.

To address these issues, recent studies mainly focus on nanostructure design, composite material development, electrolyte optimization, and large-scale preparation techniques. The emergence of silicon-carbon composite materials, which embed silicon nanoparticles into a porous carbon matrix, can construct a good conductive network, effectively improving material conductivity, and further enhance the buffering capacity for silicon volume changes, significantly improving battery cycle stability and rate performance. In this paper, a porous silicon-carbon layered silicon-based composite was prepared as an anode material. In addition, the electrochemical performance of this material was also investigated.

In the preparation process, silicon nanopowder was first uniformly dispersed with a mixed solvent of deionized water and anhydrous ethanol, and then sonicated under ultrasound to ensure uniform dispersion of silicon nanopowder. Subsequently, PVP (polyvinylpyrrolidone) and glucose/sucrose were added to the dispersed suspension as a pore-forming agent and two carbon sources, and stirred at room temperature to form a uniform precursor sol. The two precursor sols, i.e., Si/PVP/glucose and Si/PVP/sucrose, were placed into the ink cartridges of a microelectronic printer, and the gels were uniformly printed onto copper foil by a 3D printing technology. Finally, the carbon-containing substances in the electrode were completely reduced to amorphous carbon after vacuum drying and carbonization treatment. Note that different carbon sources (i.e., glucose and sucrose) released different amounts of gas during the carbonization process, leading to subtle changes in the electrode structure and subsequently affecting its electrochemical performance.

The prepared electrode materials were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and other characterization techniques.

The results show that larger pores with a uniform pore distribution exist in Si@PVP/glucose structure, and the electrode exhibits minimal cracking after charging and discharging cycles, demonstrating the superior mechanical stability and resistance to expansive internal stresses. In contrast, the pore distribution of Si@PVP/sucrose is relatively uneven, and the electrode exhibits greater cracking after cycling, leading to a decrease in cycle stability and electrochemical performance. These results demonstrate that the Si@PVP/glucose structure electrode exhibits a greater ability to withstand expansive internal stresses and has a higher cycle retention rate. The electrochemical performance tests further validate the superiority of the Si@PVP/glucose composite material. After 100 cycles of charging and discharging, the specific capacity of the Si@PVP/glucose electrode reaches 1095 mA·h·g^-1, with a reversible capacity retention rate of 97.4%, while the specific capacity of the Si@PVP/sucrose electrode is only 970 mA·h·g^-1, with a reversible capacity retention rate of 91.0%. It is indicated that the Si@PVP/glucose composite material has significant advantages in optimizing the performance of porous silicon-based anode materials, particularly in improving cycle stability and rate performance.

This study prepared a porous silicon-carbon layered silicon-based composite (i.e., Si@PVP/glucose) as an anode material, and the performance was optimized. The results showed that the Si@PVP/glucose electrode material exhibited a greater ability to withstand expansive internal stresses and had a higher cycle retention rate. The electrochemical performance tests further validated the superiority of the Si@PVP/glucose material. It is indicated that this porous silicon-based anode material could have a promising application potential in the field of energy storage and conversion for high-energy-density and long-life batteries.