Electronic structure and absolute band edge position of tetragonal AgInS2 photocatalyst: A hybrid density functional study

Energy bands, effective mass of carriers, absolute band edge positions and optical properties of tetragonal AgInS₂ were calculated using a first-principles approach with the exchange correlation described by B3LYP hybrid functional. The results indicate that tetragonal AgInS₂ has a direct band gap of 1.93 eV, which reproduce well experimental value. Calculated effective masses of electrons and holes are both small which are beneficial to separation and migration of electron and hole pairs. This implies that AgInS₂ has good photocatalytic performance. The calculated optical characteristics indicate that AgInS₂ has a slight anisotropy for both the real and imaginary parts of the dielectric function and exhibits large optical absorption in the visible light region. Furthermore, the calculated band edge positions in (100), (010) and (001) surfaces indicate that tetragonal AgInS₂ is beneficial to the reduction and oxidation of water to hydrogen and oxygen under visible light irradiation.     

Two-step pyrolytic engineering to form porous nitrogen-rich carbons with a 3D network structure for Zn-air battery oxygen reduction electrocatalysis

It is of great urgency to design inexpensive and high-performance oxygen reduction reaction (ORR) electrocatalysts derived from biowastes as substitutes for Pt-based materials in electrochemical energy-conversion devices. Here we propose a strategy to synthesize three-dimensional (3D) porous nitrogen-doped network carbons to catalyze the ORR from two-step pyrolysis engineering of biowaste scale combined with the use of a ZnCl₂ activator and a FeCl₂ promotor. Electrochemical tests show that the synthesized network carbons have exhibited comparable ORR catalytic activity with a half-wave potential (~0.85 V vs. RHE) and outstanding cyclical stability in comparison to the Pt/C catalyst. Beyond that, a high electron transfer number (~3.8) and a low peroxide yield (<7.6%) can be obtained, indicating a four-electron reaction pathway. The maximum power density is ~68 mW cm^?2, but continuous discharge curves (at a constant potential of ~1.30 V) for 12 h are not obviously declined in Zn-air battery tests using synthesized network carbons as the cathodic catalyst. The formation of 3D porous structures with high BET surface area can effectively expose the surface catalytic sites and promote mass transportation to boost the ORR activity. This work may open a new idea to prepare porous carbon-based catalysts for some important reactions in new energy devices.     

Relationship between the adhesion properties of UV-curable alumina suspensions and the functionalities and structures of UV-curable acrylate monomers for DLP-based ceramic stereolithography

Digital light processing (DLP)-based ceramic stereolithography has attracted significant attentions due to the high printing speed and high dimensional accuracy of DLP printers. However, undesired dropping of unfinished ceramic parts during printing, owing to inadequate adhesion between the first cured layer and the substrate of the building platform, still remains a challenge. In this study, the relationship between the adhesion properties of ultraviolet (UV)-curable alumina (α-Al₂O₃) suspensions and the functionalities and structures of UV-curable acrylate monomers was investigated. With an increase in the proportions of monofunctional monomers, the adhesion abilities of UV-curable alumina suspensions enhanced because of reduced volume shrinkage, however, inferior curing performances were observed due to a decrease in the double bond densities. Furthermore, the large-volume branched chain structures in monofunctional monomers and ethyoxyl groups in polyfunctional monomers effectively decreased the volume contraction, improving the adhesion performances of UV-curable alumina suspensions and facilitating the conversion of double bonds to provide excellent curing properties, further guaranteeing strong adhesion of these suspensions to the substrate.     

Electrolyte flow optimization and performance metrics analysis of vanadium redox flow battery for large-scale stationary energy storage

Vanadium redox flow battery (VRFB) is the best choice for large-scale stationary energy storage, but its low energy density affects its overall performance and restricts its development. In order to improve the performance of VRFB, a new type of spiral flow field is proposed, and a multi-physics coupling model and performance metrics evaluation system are established to explore the electrolyte distribution characteristics. The results show that the new spiral flow field can effectively improve the uniformity of electrolyte flow and alleviate the phenomenon of local concentration polarization as compared with the traditional serpentine flow field and parallel flow field. Due to the long flow channel and large pressure drop, the system efficiency is low. However, coulombic efficiency, voltage efficiency and energy efficiency are significantly better than the traditional flow fields. Therefore, the novel flow field has obvious advantages in the application of small stacks.     

Tensions in governing megaprojects: How different types of ties shape project relationship quality?

Faced with increasing governance tensions to cope with conflicts and risks associated with megaprojects, relationship management is seen as an essential aspect for improving relationship quality and achieving project success. Drawing upon transaction cost theory, this study investigated the effects of two types of ties (relational ties and structural ties) on relationship quality. Data from 212 megaproject practitioners were analyzed by structural equation modeling (SEM) and fuzzy-set qualitative comparative analysis (fsQCA). The SEM revealed the indirect effects of two types of ties on relationship quality and the mediating role of contractual functions in the management of relationships. Through the lens of symbiosis, the fsQCA revealed three types of configurations that were sufficient for shaping relationship quality. This study provides a systematic and nuanced distinction between multi-dimensional strengths of ties and contractual functions in project management. Such knowledge would allow megaproject managers to develop effective interventions aimed at enhancing relationship quality.     

β-FeOOH modified carbon monolith anode derived from wax gourd for microbial fuel cells

The preparation of high-performance anode materials is of significance for enhanced power generation in microbial fuel cells (MFCs). Herein, porous carbon monolith was prepared by simple freeze drying of wax gourd and subsequent pyrolysis (WGC). β-FeOOH was coated on WGC to further improve the performance of the anode (β-FeOOH/WGC). The maximum power density of the MFCs with WGC and β-FeOOH/WGC anode was 913.9 and 1355.1 mW/m² respectively, which was much higher than that of the control (558.2 mW/m²). WGC possessed three-dimensional pore structure, nitrogen and oxygen-containing functional groups, which endowed it with satisfactory bacterial loading. Improved MFC performance after β-FeOOH modification could be ascribed to two aspects: β-FeOOH enhanced the electrochemical activity and decrease the transfer resistance; β-FeOOH was conducive to exoelectrogens formation. This study demonstrated that the synthesis of β-FeOOH modified carbon monolith anode offered an efficient route to enhance the power generation of MFCs.     

Coupling Characteristics of a Co-flow Water Mist System and Normal Temperature Counter Air Jets

Fire Technology - A co-flow water mist system is considered a clean and efficient emergency handling measure for preventing and controlling the leakage of hazardous gas. To reveal the coupling...     

Effect of coral sand powders and seawater salinity on the impact mechanical properties of cemented coral sand

Coral sand is one kind of the important building materials in coral reef engineering practice. The use of cement as a stabilizing agent can significantly improve the mechanical properties of coral sands and is widely applied in the subbase engineering construction in coral reef islands. Cement-stabilized coral sand structures may contain high contents of fine coral particles and salinity because of the high crushability of coral sands and the existence of seawater surrounding them. In this study, the effects of coral sand powders and seawater salinity on the dynamic mechanical properties of cemented coral sand (CCS) were investigated through the split Hopkinson pressure bar (SHPB) tests and Scanning Electron Microscope (SEM) analysis. It was found that the strength (i.e., the peak stress) of CCS specimens increased firstly and then decreased with the increase of powder content. The specimens reached the maximum peak stress when 3% powder content was included. The initial improvement of CCS strength was attributed to the pore-filling effect of coral powders, namely, the micro pores of the CCS specimens could be more effectively filled with higher percentages of coral powders being used in the experiments. However, excessive coral powders resulted in the reduction of specimen strength because these powders could easily be cemented into agglomerates by absorbing water from the specimens. These agglomerates could reduce the cementation strength between the coarse coral particles and the cement. Meanwhile, the peak stress of CCS specimens was found to be negatively correlated with the average strain rate and the ultimate strain. The degree of specimen fracture was found to be correlated with the amount of specific energy absorption during the tests. Furthermore, the “sulfate attack” caused by the inclusion of salinity of water had different influences on the CCS specimens with different coral powder contents. The ettringite and gypsum produced in “sulfate attack” could fill the pores and lead to cracking of the specimens, significantly affecting the specimen strength.     

Constructing the high-areal-capacity,solid-state Li polymer battery via the multiscale ion transport pathway design

The parasitic Li dendrite formation and retarded ion diffusion dynamics inhibit the deployment of solid-state batteries (SSBs) at high areal capacity loadings. Here, we present the modular design of the Li⁺ percolating network by grafting the ionic-conductive polyether amine (PEA) at the multiple scales: the PEA modified zinc hydroxystannate (PEA@ZHS) (flame retardant units) and polyamide 6 (mechanical rigid units) are coherently introduced to optimize the PEO-based solid electrolyte (PX-PEA@ZHS) with the Young's modulus (3.41 GPa), ionic conductivity (4.29 × 10⁻⁴ S cm⁻¹ at 55 °C) and flame retardancy (22% reduction of heat release rate); on the other hand, PEA molecules are grafted onto the acetylene black additive to establish the dual conductive network, endowing two orders of magnitude increase of ionic conductivity for the high-compaction cathodes. The as-integrated symmetric cell exhibits a critical current density up to 0.8 mA cm⁻² and cycling endurance for 1000 h at 0.2 mA cm⁻²; upon the SSBs assembly with the record high loading of LiFePO₄ (12.4 mg cm⁻²), the high-areal-capacity, cycling stability as well as the extreme temperature endurance till 110 °C are simultaneously realized, which inspire the rational design of commercially feasible, energy-dense, flame-resistance energy storage prototype.