Material property differences among components of solid oxide fuel cell (SOFC) lead to excessive stresses during cell fabrication and operation, among which functional gradient material electrodes have attracted attention for their ability to reduce residual and thermal stresses in SOFC. But so far, there is rare study on SOFC with functional gradient anode using numerical simulation of thermal stress. In this study, a multi-physics field coupling model of SOFC with complete structure was established by COMSOL Multiphysics 6.0. Based on multi-physics field coupling model and numerical simulation of the residual stresses and thermal stresses in SOFC, four different distribution curves were employed to characterize the component distribution of anode materials. The results show that the tensile stress of anode can be significantly reduced by using functional gradient material during fabrication at different temperatures, especially at room temperature. Compared with non-gradient distribution, the maximum tensile stress of the anode is reduced by 47.69% before reduction and 35.74% after reduction by using quadratic curve distribution. During the operation process, the heat generated by the electrochemical reaction and the convective heat transfer of gas leads to the temperature difference between inlet and outlet, resulting in significant stress concentration at inlet and outlet of the metal frame as well as at contact surface between rib and electrode. Functional gradient materials can significantly reduce the maximum stress on the anode, metal frame and electrolyte, which is particularly obvious when using quadratic curve distribution. Therefore, this research has potential theoretical significance and engineering value for designing and fabricating SOFCs.

The fabrication of large-area, high-efficiency perovskite solar cell module (PSM) represents a pivotal stage in the industrialization of perovskite solar cells (PSCs). Leveraging volatile solvents within perovskite precursors is a streamlined approach which offers distinct advantages in the industrialization trajectory of PSCs, but often exhibits accelerated crystallization kinetics, diminutive grain dimensions and elevated defect densities within the films, consequently compromising device efficiency and stability. This study devised a volatile solvent system comprising methylamine/acetonitrile (MA/ACN) for the production of MAPbI₃ perovskite solar cells/module. Incorporation of an optimal quantity of PbCl₂ into the perovskite precursor solution served to retard crystallization kinetics and passivate grain boundary imperfections. Notably, small-area device fabricated via this methodology demonstrated a peak photovoltaic conversion efficiency (PCE) of 21.21%, alongside enhanced operational stability. Furthermore, PSM engineered through this approach achieved a PCE of 18.89%. This study presents a novel paradigm for advancing the large-scale industrial manufacturing of PSCs.

Carbon-based perovskite solar cells (C-PSCs) have attracted significant interest for their advantages of high photoelectric conversion efficiency (PCE), long-term stability and low cost, showing superiority in commercialization of perovskite solar cells (PSCs). However, the promoting effect of PbTiO₃ modification and polarization treatment on C-PSCs photovoltaic performance by in-situ generation of PbTiO₃ on a dense electron transport layer of TiO₂ (c-TiO₂) is still unknow.. It was found that the PbTiO₃ formed after reaction for 30 s could effectively restrict the sharp increase in resistance of the electron transport layer, and substantially reduced the carrier accumulation at the interface to 29.7%, greatly improving the carrier separation ability. In addition, the carrier accumulation was further reduced to 6.78% through polarizing the c-TiO₂/PbTiO₃ layer, so that PSCs displayed 0.93 V of open circuit voltage (V_oc), 14.83 mA/cm² of short circuit current density (J_sc), 51.16% of fill factor (FF), and 7.11% of PCE. This work comprehensively reports the methods of PbTiO₃ modification and polarization treatment, proposes a research strategy to improve the performance of C-PSCs, reveals the intrinsic mechanism for optimizing carrier transport performance, and provides a way for developing high-efficiency, low-cost and long-life commercial PSCs.

MXenes with two-dimensional layered structure are widely used in the field of potassium ion supercapacitors because of their excellent electrical properties and adjustable surface functional groups, but their limited dual-capacitor storage capacity severely retards the application of MXenes materials in electrode materials. In this work, the strategy of “Lewis acid molten salt pre-etching + liquid phase etching + in situ hydrothermal recombination” was used to prepare the Ti₃C₂-based heterojunction with Ti₃C₂ as matrix and MnO₂ coated surface to improve the storage of potassium ions in electrode materials. The connection mode, electrical properties and the change of potassium adsorption law at Ti₃C₂-based heterojunction interfaces were studied by using the first principles calculation method based on density functional theory. The results show that the maximum adsorption capacity of potassium ions in the constructed Ti₃C₂-based heterojunction is about 3 times that of Ti₃C₂. The presence of Ti-O-H-O connecting channel increases the number of free electrons in MnO₂, causing Ti₃C₂-based heterojunction exhibiting excellent electrical properties. The electrochemical test results of the three-electrode system show that, at a current density of 1 A·g^-1, Ti₃C₂-based heterojunction can provide 431 F·g^-1 specific capacitance which is much higher than 128 F·g^-1 of bare Ti₃C₂. At a voltage sweep rate of 100 mV·s^-1, the contribution of pseudocapacitance is up to 89%. In addition, the Ti₃C₂-based heterojunction exhibits lower electrochemical impedance, which improves the potassium ion transport rate and electron transfer rate. Therefore, this study demonstrates that the electrochemical performance of Ti₃C₂ matrix can be improved by constructing Ti₃C₂-based heterojunction, and the corresponding energy storage mechanism can provide a theoretical basis for the design of other MXenes-based electrode materials.

Ag₂Se-based thermoelectric films and devices have become a popular research topic in the field of wearable thermoelectric energy conversion due to their narrow bandgap semiconductor properties, which exhibit good thermoelectric properties at room temperature. These films are typically constructed by stacking nanoparticles, and the dimensions of nanomaterials significantly impact the thermoelectric transport properties of the network. In this study, Ag₂Se nanomaterials with different dimensions were prepared by solvothermal and template methods, and flexible Ag₂Se thermoelectric films were constructed on polyimide substrates using Ag₂Se nanomaterials with different dimensions by spraying process combined with high-temperature post processing. The effects of the dimensionality of Ag₂Se nanomaterials on the microstructures and thermoelectric properties of the films were then systematically investigated. Zero dimensional Ag₂Se nanoparticles exhibited superior conductive networks and thermoelectric properties in comparison to one dimensional nanowire structures. Furthermore, the room temperature power factor of the films reached 199.6 μW·m^-1·K^-2, and the power factor was 257.9 μW·m^-1·K^-2 at the temperature of 375 K, which indicated the good thermoelectric properties of the films. Additionally a device was designed and integrated based on the Ag₂Se films, with four thermoelectric arms and excellent performance. The device exhibited good mechanical flexibility and output performance with internal resistance increased by only 8.2% after 1000 bending cycles (bending radius: 20 mm), and the device displayed an open-circuit voltage of 9.1 mV and a max output power of 43.7 nW at a temperature difference of 30 K. This study presents a novel approach for the preparation of flexible Ag₂Se-based thermoelectric thin-film materials and devices.

CaBi₂Nb₂O₉ (CBN) thin films with a bismuth layered structure are important precursors for ferroelectric memories, due to their high fatigue resistance, and good ferroelectric properties. The epitaxial growth of CBN along the a-axis is desirable for the integration and application. However, the structural anisotropic makes it challenging to regulate the polarization with respect to the crystallography. In this paper, a new strategy is proposed for the growth of a-axis oriented CBN thin films on MgO(100) single crystal substrate. This strategy is realized by changing the deposition temperature using the pulsed laser deposition technique. The CBN thin films are grown along (115)-, (200)-, and (00l)-crystallographic direction, when the films are deposited at 500, 600 and 700 ℃, respectively. As the deposition temperature increases, the CBN films undergo (115)-(200)-(00l) orientation transition. Meanwhile, SEM results show that 600 ℃ is the optimal deposition temperature for high-quality a-axis epitaxial growth of CBN films on MgO substrates. Under this condition, the films are well bonded to the substrate with a low roughness. HRXRD and HRTEM analyses show that the (200)-oriented CBN films are heterogeneous epitaxial growth, forming a semiconformal lattice interface between the (200)-oriented CBN film and the MgO substrate, also revealing a crystallographic relationship between the as-grown thin film and the substrate, i.e., (100)[001]CBN//(100)[001]MgO. The average (200) spacing at the CBN/MgO interface was measured to be 0.5312 nm. Based on the lattice-matching relationship, a theoretical model is proposed that four CBN unit cells matching five MgO unit cells. Moreover, the nanodomain structure of the (115)-oriented CBN thin films and the out-of-plane polarization switching of the (200)-oriented CBN thin films are demonstrated by PFM.

Preparation of carbon-carbon composites through the chemical vapor infiltration (CVI) process, utilizing CH₄ and C₂H₅OH as precursors, can effectively improve the deposition rate and produce highly structured pyrolytic carbon. Understanding the reaction mechanism is essential for computational fluid dynamics (CFD) studies. Chemical reaction mechanisms typically involve numerous free radicals and reactions, and manually constructing such mechanisms based on experimental data alone risks omitting critical species and reactions. Hence, in this research, a thorough gas-phase pyrolysis kinetic mechanism for the CH₄+C₂H₅OH+Ar system was developed using the reaction mechanism generator (RMG). This mechanism included 31 core species and 214 core reactions, accurately predicting the evolution of major species' formation and consumption. The simulation results were consistent with experimental observations. Through a detailed analysis of the kinetics and sensitivity of reactants and critical products, reactions influencing the formation and consumption of crucial species were identified. Reaction pathway analysis further clarified relationships among different species, identifying core species within the mechanism. By simplifying the detailed mechanism based on sensitivity and rection pathway analysis at 1373 K and 10 kPa, a gas-phase kinetic mechanism was derived, composed of 18 species and 44 reactions. This streamlined model substantially boosts computational efficiency while retaining key species, providing a more convenient foundation for further CFD studies and applications.

Ammonia is a harmful atmospheric pollutant that poses serious threats to human health and ecological environment. Therefore, the development of low-energy, high-performance and real-time ammonia monitoring system is imperative. In this study, p-aminobenzene sulfonic acid (pABSA) modified MoO₃/polypyrrole (PPy) composite materials were successfully prepared using an in situ chemical oxidation polymerization method with MoO₃ and pyrrole monomer (Py) as raw materials and FeCl₃ as an oxidant, along with pABSA as an anionic surfactant. Microstructure of the materials was characterized to explore influence of pABSA-modified MoO₃/PPy composite materials on the gas sensing performance. The results demonstrate that at room temperature, the response value of pABSA-modified MoO₃/PPy composite material to a mass concentration of 1×10⁵ µg/L ammonia is 188%, which is ~8 times higher than that of pure PPy (22%), exhibiting excellent selectivity and stability. The enhancement in sensing performance can be attributed to the formation of a heterojunction between MoO₃ and PPy as well as surface modification by pABSA leading to increased mobile charge carriers on the material's surface.

Hydrogen generation from electrolyzed water has received extensive attention in the scientific community due to its green and environmentally friendly properties, as well as the high purity of hydrogen produced. However, the slow oxygen evolution reaction (OER) during electrocatalytic water splitting has significantly hampered the development of hydrogen production, posing numerous challenges in its practical application. In this study, a novel three-dimensional (3D) core-shell heterostructure catalyst with crystalline NiMoO₄ nanorods as “core” and amorphous CoFe-LDH nanosheets as “shell” was successfully fabricated on a conductive nickel foam (NF) substrate by using a combination of hydrothermal and electrodeposition strategy. This special 3D core-shell structure fully stimulates the electrocatalytic potential of NiMoO₄ and CoFe-LDH, which greatly enhances the efficiency of the overall water-splitting. Through the synergistic interaction of NiMoO₄ and amorphous CoFe-LDH, the NiMoO₄@CoFe-LDH/NF nanocatalysts generates more active sites and exhibits highly efficient electron transfer ability and excellent OER electrocatalytic activity. Electrochemical tests show that NiMoO₄@CoFe-LDH/NF exhibits the most excellent electrochemical performance when the electrodeposition time is 60 s. The overpotentials η₁₀ and η₁₀₀ at 10 and 100 mA·cm⁻² are only 168 and 216 mV, respectively, which shows a very small Tafel slope and excellent long-term stability. Meanwhile, the overall water-splitting system of NiMoO₄@CoFe-LDH||NiMoO₄ exhibits a low driving voltage, which can produce a current density of 10 mA·cm⁻² at 1.57 V. In conclusion, this work provides new ideas for design and development of efficient catalytic materials for electrolyzed water.

In the process of electrolyzing water to produce hydrogen, the sluggish electrocatalytic kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) limit the energy conversion efficiency. High-entropy materials have been considered as potential catalysts due to their unique structural features and excellent performance, which could potentially replace traditional metal oxides and precious metals for energy conversion and water electrolysis. Due to the incompatibility between different metals and non-metals, there have been few reports on the synthesis of high-entropy compounds, especially high-entropy metal phosphides. In this study, a series of carbon-based high-entropy alloy phosphide nanoparticles were synthesized using citric acid as complexing agent and ammonium dihydrogen phosphate as phosphorus source via a low-temperature Sol-Gel method with different elemental metals. In 1 mol·L^-1 KOH solution, FeCoNiMoCeP/C exhibited good water electrolysis performance at a current density of 10 mA·cm^-2, with overpotentials of 119 and 240 mV for the HER and OER, respectively. Similarly, in overall water splitting studies, FeCoNiMoCeP/C also showed excellent catalytic activity. When operating at a current density of 10 mA·cm^-2, FeCoNiMoCeP/C required only 1.53 V as the combined anode and cathode voltage for electrolyzing water. This is due to the synergistic effects among the atoms of high-entropy phosphide catalysts which provide more reaction sites to increase reaction activity and selectivity. This study is expected to expand the potential applications of high-entropy alloys in the field of electrocatalysis.

Amorphous calcium carbonate (ACC) plays a crucial role in biomineralization which crystallization process has attracted significant attention. Magnesium ions (Mg²⁺) can effectively regulate the crystallization of ACC, but the mechanism by which it controls the transformation of ACC into monohydrocalcite (MHC, CaCO₃·H₂O) is not well understood. In this study, Mg²⁺ was used as an additive, and the transformation process from ACC to MHC was investigated in situ using an automatic potentiometric titration system. It was found that Mg²⁺ can enhance the stability of ACC and inhibit the formation of calcite and vaterite. During the transformation of ACC to MHC, partial dissolution firstly occurred, and the molar ratio of Mg/Ca in the solution increased with the consumption of Ca²⁺. Mg²⁺ further adsorbed onto the surface of ACC particles, inhibiting surface dissolution of ACC and promoting internal dissolution of ACC, resulting in the formation of hollow structures rich in Mg²⁺ and smaller-sized nanoparticles. Subsequently, MHC crystallized and grew through particle aggregation. These results elucidate the mechanism by which Mg²⁺ regulates the transformation of ACC into MHC through a non-classical crystallization pathway, enhancing an understanding of the biomineralization mechanism from ACC precursor.

Based on Peltier effect, Bi₂Te₃-based alloy is widely used in commercial solid-state refrigeration at room temperature. The mainstream strategies for enhancing room-temperature thermoelectric performance in Bi₂Te₃ focus on band and microstructure engineering. However, a clear understanding of the modulation of band structure and scattering through such engineering remains still challenging, because the minority carriers compensate partially the overall transport properties for the narrow-gap Bi₂Te₃ at room temperature (known as the bipolar effect). The purpose of this work is to model the transport properties near and far away from the bipolar effect region for Bi₂Te₃-based thermoelectric material by a two-band model taking contributions of both majority and minority carriers into account. This is endowed by shifting the Fermi level from the conduction band to the valence band during the modeling. A large amount of data of Bi₂Te₃-based materials is collected from various studies for the comparison between experimental and predicted properties. The fundamental parameters, such as the density of states effective masses and deformation potential coefficients, of Bi₂Te₃-based materials are quantified. The analysis can help find out the impact factors (e.g. the mobility ratio between conduction and valence bands) for the improvement of thermoelectric properties for Bi₂Te₃-based alloys. This work provides a convenient tool for analyzing and predicting the transport performance even in the presence of bipolar effect, which can facilitate the development of the narrow-gap thermoelectric semiconductors.

Platinum (Pt)-based noble metal catalysts (PGMs) are the most widely used commercial catalysts, but they have the problems of high cost, low reserves, and susceptibility to small-molecule toxicity. Transition metal oxides (TMOs) are regarded as potential substitutes for PGMs because of their stability in oxidizing environments and excellent catalytic performance. In this study, comprehensive investigation into the influence of elastic strains on the adsorption energies of carbon (C), hydrogen (H) and oxygen (O) on TMOs was conducted. Based on density functional theory (DFT) calculations, these effects in both tetragonal structures (PtO₂, PdO₂) and hexagonal structures (ZnO, CdO), along with their respective transition metals were systematically explored. It was identified that the optimal adsorption sites on metal oxides pinpointed the top of oxygen or the top of metal atom, while face-centered cubic (FCC) and hexagonal close-packed (HCP) holes were preferred for the transition metals. Furthermore, under the influence of elastic strains, the results demonstrated significant disparities in the adsorption energies of H and O between oxides and transition metals. Despite these differences, the effect of elastic strains on the adsorption energies of C, H and O on TMOs mirrored those on transition metals: adsorption energies increased under compressive strains, indicating weaker adsorption, and decreased under tension strains, indicating stronger adsorption. This behavior was rationalized based on the d-band model for adsorption atop a metallic atom or the p-band model for adsorption atop an oxygen atom. Consequently, elastic strains present a promising avenue for tailoring the catalytic properties of TMOs.