Search Results (12,456)

Facing the dual challenges of energy shortage and environmental degradation, photocatalysis and electrocatalysis have emerged as key technologies for converting small molecules into value-added chemicals, yet their conflicting requirements on the electronic structure of catalysts prevent a single material from freely switching between the two modes. Here, we demonstrate a feasible strategy for achieving on-demand switching between these catalytic functions in a single ferroelectric heterojunction, Pd-C₃N₄@In₂Se₃, through polarization engineering. Using first-principles density functional theory calculations, we show that reversing the polarization direction of the α-In2Se3 layer induces a nonvolatile electronic phase transition. The downward polarization (P↓) configuration exhibits metallic behavior, whereas the upward polarization (P↑) state becomes semiconducting with a type-II band alignment. This transition arises from polarization-dependent interfacial built-in electric fields and charge transfer differences. Notably, the metallicity of the P↓ configuration is localized predominantly within the In₂Se₃ layer rather than delocalized over the entire heterostructure. This arises because the enhanced interfacial charge transfer, driven by the larger work-function difference, selectively populates the conduction band of In₂Se₃, pushing its band edge across the Fermi level, while the Pd-C₃N₄ layer remains semiconducting due to charge depletion and the absence of gap-closing hybridization at the interface. In the P↑ state, the heterojunction acts as an efficient photocatalyst for overall water splitting, with band edges straddling the redox potentials. Under illumination, photogenerated electrons and holes make the hydrogen evolution reaction and oxygen evolution reaction thermodynamically spontaneous. In contrast, the metallic P↓ state serves as an excellent electrocatalyst for hydrogen evolution, delivering a limiting potential as low as −0.11 V, attributed to strengthened N 2p and H 1s orbital hybridization. These findings resolve the conflicting electronic requirements of photocatalysis and electrocatalysis and offer a new paradigm for designing smart, dual-functional catalysts adaptable to varying energy inputs, providing valuable theoretical guidance for future experimental realization of switchable catalytic systems. Full article

With the high-proportion integration of renewable energy, integrated energy systems face greater demands regarding renewable energy utilisation, power balancing, and operational efficiency. By aggregating distributed generation, energy storage and load resources, integrated energy systems can provide effective support for multi-energy coordinated scheduling. This paper proposes a 24 h day-ahead multi-objective optimal scheduling framework for an integrated hydro–wind–photovoltaic–storage energy system based on multi-objective particle swarm optimisation (MOPSO). Firstly, this paper establishes mathematical models for wind power, photovoltaic (PV), hydropower, and energy storage units. Subsequently, it incorporates the outputs of hydropower, wind power, PV, and storage, along with the charging and discharging of energy storage and the process of purchasing electricity from and selling electricity to the main grid, into a unified optimisation model. The objectives are to maximise economic benefit and variable renewable energy utilisation while minimising the peak-to-valley difference in residual load. To address the conflicts between these multiple objectives, a MOPSO algorithm combined with a normalised weighted scoring method is employed to select a compromise optimal solution. Results from case studies based on typical days of the four seasons and various operational strategies demonstrate that the proposed method can rationally allocate the outputs of different energy sources, reduce the system’s dependence on the main grid, and improve variable renewable energy utilisation, thereby providing a reference for the optimal scheduling of integrated energy systems. Full article

Off-grid photovoltaic (PV) hydrogen production systems must coordinate rapidly varying PV power, battery energy, and the operating states of multiple alkaline water electrolyzers. Inappropriate coordination may lead to PV curtailment, frequent unit switching, and persistent workload concentration on a small number of electrolyzers. This paper develops an efficiency- and load-balanced operation (ELBO) scheme as an improved rule-based supervisory strategy rather than an online optimization method. ELBO adopts a two-level decision structure. A planned number of online electrolyzers is first determined from the moving-average PV power and the reference power associated with high single-unit efficiency. This planned count is then corrected using real-time PV power, battery state of charge, and the previous electrolyzer states. The controller adjusts the powers of the online units before changing their number, uses the battery to bridge temporary power deficits, and distributes the remaining adjustable power under the operating and ramp-rate constraints. Five representative PV profiles selected from one year of measured data were used to compare ELBO with PV-following operation (PFO), multi-electrolyzer coordinated operation (MECO), and an offline mixed-integer linear programming (MILP) benchmark. ELBO produced 1328 kg of hydrogen, which was 8.85% and 6.07% higher than PFO and MECO, respectively. Its overall PV-to-hydrogen efficiency and PV utilization reached 65.2% and 94.9%, respectively, with 36 start–stop events. MILP produced 1345 kg of hydrogen, only 1.28% more than ELBO, but required the complete future PV sequence. Ablation analysis further shows that the planned-count layer, moving-average filtering, battery-supported retention, and load-balancing allocation contribute to different and complementary aspects of capacity matching, operating continuity, and workload distribution. The results indicate that the benefit of ELBO arises from the ordered coordination of these supervisory functions and that it provides a practical compromise between operating performance, workload distribution, information requirements, and computational complexity under the representative conditions considered. Full article

Defect calculations for semiconductors demand both large supercells and accurate electronic structures, posing a significant challenge to first-principles methods. Conventional density functional theory (DFT) with local or semi-local exchange-correlation functionals severely underestimates the band gap, whereas hybrid functionals such as HSE06 provide higher accuracy but at a substantially increased computational cost. In this work, we demonstrate that shell DFT-1/2, a self-energy correction method for electronic structure calculations, may be used jointly with HSE06 to reach the optimal efficiency as well as accuracy. In particular, indium phosphide (InP) was taken as an example. The shell DFT-1/2 method was utilized to yield accurate band structures with a 1.44 eV direct gap, without any empirical parameter. Subsequently, the portion of exact exchange was tuned to match the shell DFT-1/2 electronic structure in HSE06 calculations. The charge transition levels of various point defects in InP were derived using HSE06, and HSE06 and shell DFT-1/2 may be employed alternatively to yield the density of states for the defective supercells. Their consistency proves the feasibility of the complementary employment of the two methods, and this strategy is readily extendable to other semiconductor research. Full article

The decarbonization of maritime transportation requires shipboard energy systems to coordinate conventional generators, renewable energy sources, energy storage devices, and thermal energy units under voyage-dependent operating constraints. This paper develops a configurable hybrid multienergy ship system for coordinated electrical and thermal energy scheduling. The proposed framework functionally separates the propulsion subsystem from the service and thermal subsystem while retaining system-level coordination among photovoltaic generation, wind generation, diesel generators, micro gas turbines, energy storage batteries, and thermal energy units. A convolutional neural network is employed to provide short-term photovoltaic power forecasts for day-ahead scheduling. The resulting scheduling problem simultaneously considers voyage completion, power balance, equipment operating limits, ramp-rate constraints, battery charging and discharging restrictions, operating costs, and pollutant emission treatment costs. The nonlinear operating logic is reformulated as a mixed-integer optimization problem and solved using CPLEX. A representative coastal voyage case study is used to evaluate the proposed framework. The results demonstrate that the method can coordinate multiple shipboard energy sources, satisfy the prescribed electrical and thermal demands, and provide a set of Pareto-optimal solutions describing the trade-off between operating cost and emission-related cost. The proposed framework provides a system-level scheduling approach for supporting the economic and low-carbon operation of hybrid multienergy ships under increasingly stringent maritime emission reduction requirements. Full article

The piezocatalytic activity of metal–organic frameworks (MOFs) is generally hampered by an insufficient intrinsic piezoelectric response, which largely restricts their application in energy catalytic conversion. Herein, MIL-125-NH₂(Ti) (denoted NM) was chosen as a prototypical model to demonstrate that defect engineering serves as an efficient strategy to simultaneously reinforce the piezoelectric characteristics and piezocatalytic hydrogen evolution performance of MOFs. Multiple comprehensive characterizations verify that thermally treated NM-250 (NM thermally treated at 250 °C under flowing N₂ atmosphere) contains abundant in situ-generated oxygen vacancies. These defects disrupt the high intrinsic structural symmetry of pristine NM and promote the establishment of polarized electric fields upon mechanical excitation. Electrochemical measurements further reveal that the introduced oxygen vacancies effectively suppress charge carrier recombination and accelerate interfacial charge transfer, thereby facilitating the piezocatalytic hydrogen evolution reaction. Benefiting from the optimized piezoelectric polarization and improved charge separation efficiency, NM-250 delivers a piezocatalytic H₂ production rate of 413.5 μmol g⁻¹ h⁻¹, exceeding the value of pristine NM (180.9 μmol g⁻¹ h⁻¹) by 2.28 times. This work elucidates the underlying mechanism by which oxygen vacancy defects modulate piezoelectric polarization and catalytic kinetics and validates defect engineering as a promising route to construct high-performance MOFs-based piezocatalysts. Full article

The development of efficient photocatalysts for hydrogen production is a key challenge for sustainable energy technologies. In this study, strontium titanate (SrTiO${}_3$) was synthesized via a citrate-assisted sol-gel method and subsequently modified by deposition-precipitation using nominal HAuCl${}_4$ precursor concentrations of 1.0, 1.5, and 2.0 mM. The resulting materials were characterized by XRD, Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy, SEM with EDS, and X-ray fluorescence (XRF). Au incorporation did not produce detectable changes in the SrTiO${}_3$ crystalline phase or its optical band gap, which remained at 3.19–3.20 eV. The additional absorption band centered near 550 nm was consistent with the localized surface plasmon resonance of metallic Au nanoparticles. Microscopy indicated increasing surface coverage and aggregation at the highest nominal precursor concentration. Under irradiation with a low-pressure Hg lamp, all Au-containing materials presented substantially greater H${}_2$ evolution than pristine SrTiO${}_3$, whereas the comparatively small differences among the Au-modified samples indicated an apparent activity plateau across the evaluated concentration range. Because the Au-associated absorption band near 550 nm lies outside the main 254 nm emission of the lamp and the SrTiO${}_3$ band gap remained mostly unchanged, the enhanced H${}_2$ evolution is consistent with improved interfacial charge separation in the Au/SrTiO${}_3$ system. A Schottky-junction-mediated pathway is proposed based on the observed activity trends and the electronic properties reported for Au/SrTiO${}_3$ interfaces, rather than to a plasmonic or band-gap-tuning effect. The selected STO/Au 2.0 mM material retained approximately 97% of its initial apparent H${}_2$ evolution rate after three consecutive cycles, indicating favorable short-term activity retention. Overall, this comparatively simple synthesis route provides a practical baseline for investigating the influence of nominal Au precursor concentration on H${}_2$ evolution over SrTiO${}_3$. Full article

Inductive power transfer (IPT) is a promising charging approach for rail trams because their trajectories are fixed, lateral displacement is constrained by the rails, and charging infrastructure can be installed at predetermined locations. Nevertheless, the long vehicle body, high power demand, variable air gap, and dynamic operating conditions of rail trams impose stringent requirements on magnetic-coupler design. This study proposes a bibliometric-assisted analytic hierarchy process (AHP) framework for the comprehensive performance evaluation of magnetic couplers used in rail–tram IPT systems. The framework considers five performance dimensions: power-efficiency characteristics, spatial characteristics, power density, time characteristics, and energy-transfer capability. Bibliometric keyword-occurrence statistics are introduced as an external source of evidence to support the initial construction of AHP judgment matrices, thereby reducing the exclusive dependence of conventional AHP on the judgments of a small expert group. A 2M2T low-floor tram is used as a case study, and two magnetic-coupler configurations, namely the $2\times 1$ and $3\times 1$ configurations, are evaluated using electromagnetic and circuit-simulation results. The case study illustrates the application of the proposed framework to the comparison of magnetic-coupler configurations under the operating and installation constraints of the investigated tram. The present validation is limited to simulation-based analysis of one tram platform and two configurations; further experimental and multi-configuration validation is required. Full article

Triboelectric nanogenerators (TENGs) are promising for harvesting low-frequency mechanical energy, but rotating TENGs (R-TENGs) driven by low-speed water flow remain constrained by limited driving torque, sliding-contact losses, and rotating-system stability. Here, a three-dimensional (3D) riveted complementary-structure rotating triboelectric nanogenerator (RCSR-TENG) is proposed for low-speed water-flow energy harvesting. A semi-analytical formulation incorporating a force-dependent real-contact fraction is developed to describe the coupled relationships among output voltage, transferred charge, rotation angle, and contact force. Because the contact parameters were not independently calibrated, the formulation is used for sensitivity and trend analysis rather than as a quantitatively validated predictive model. For the single prototype tested for each configuration, at 1000 rpm under the fixed effective measurement load of 9 MΩ, the RCSR-TENG produced a peak output power of 544 μW, compared with 304 μW for the flat R-TENG, representing an increase of approximately 79%. The same RCSR-TENG prototype maintained a stable voltage amplitude of over 150,000 rotation cycles. When coupled to a fully passive flapping-foil collector in a 0.55 m s⁻¹ water flow, the system generated periodic electrical output with a peak area-normalized power exceeding 5000 μW m⁻². These results demonstrate the structural-performance advantage of the riveted complementary design and its proof-of-concept applicability to low-speed water-flow energy harvesting. Full article

Extreme weather couples spatially correlated component damage with photovoltaic (PV) derating, changing electric-vehicle (EV) demand, repair delay, and time-varying network topology. This paper develops a coordinated restoration architecture for multi-area feeders containing PV, battery energy storage, and charging stations. Its weather-facing layer constructs joint outage-risk, renewable-error, charging-demand, and voltage-vulnerability descriptors. Those descriptors parameterize a two-stage mixed-integer second-order-cone program with a finite-support optimal-transport ambiguity set that remains well defined for discontinuous mixed-integer recourse. Regional actor–critic agents propose five-minute corrections around the hourly robust schedule; constrained projection, non-linear AC power-flow screening, emergency fallback, and margin-tightened re-optimization retain the authority to accept or reject each proposal. The evaluation uses public 33-node and 123-node feeders together with synthetic 240-node and 850-node stress networks. A pre-fit manifest allocates 240 records to training, 80 to validation, and 320 to final testing, while aggregate operational outcomes cover 50 random streams. Within this controlled benchmark, accepted schedules restore 93.6% of critical-load energy (SD 2.1 percentage points), serve 96.7% of total demand (SD 1.8 percentage points), retain 82–86% of EV service across hazard classes, and reduce the modeled 24 h objective by 25.8% relative to deterministic dispatch. The full pipeline records two to four candidate-stage voltage-limit events by hazard, and 4.9% of candidates undergo tightened re-optimization before accepted schedules reach zero reported AC voltage-limit violations. Between-method comparisons are descriptive and unpaired; the larger synthetic cases are structural stress tests rather than feeder-transfer tests. Full article

Protein solubility can limit enzyme performance in industrial applications. This is the case for some carbonic anhydrases (CAs), key enzymes for CO₂ capture and utilization. In this study, we investigated an α-class CA from the thermophilic bacterium Hydrogenimonas thermophila (HtCA), which was predominantly expressed as an insoluble protein in Escherichia coli. Surface analysis using Molecular Operating Environment (MOE) revealed extensive hydrophobic regions, suggesting a basis for its poor solubility. To improve solubility, three C-terminal fusion tags were evaluated (Gb1, ng3-NEXT, and T7B9). All tagged variants showed markedly increased soluble expression as determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis. To reduce surface hydrophobicity, selected residues were substituted with charged amino acids. Most variants displayed improved solubility, and V136D showed enhanced thermostability, retaining 76% activity after exposure to 90 °C for an hour. However, the F177D variant completely lost all enzymatic activity, highlighting the importance of evaluating both solubility and catalytic function during protein engineering. Molecular dynamics simulations supported the experimental findings, revealing that thermostable variants exhibited reduced structural fluctuations and favorable free-energy landscapes, while the inactive F177D mutant sampled a broader conformational space and higher-energy conformations, consistent with decreased structural stability and loss of catalytic activity. Full article

For renewable-rich microgrids, effective energy management is essential to improve economic efficiency and renewable-energy utilization while maintaining supply adequacy and network security. However, online dispatch remains challenging because variable renewable generation and demand must be coordinated under battery operating limits, distribution-network voltage constraints, and limited forecast information. To address this challenge, this paper proposes a safety-filtered hierarchical PPO–TD3 framework for microgrid energy management. The upper PPO layer selects coarse battery operating modes for long-horizon economic scheduling, while the lower TD3 layer refines continuous battery-power commands for short-term regulation. Before execution, the fused command is projected through a model-based safety filter considering state-of-charge limits, supply-priority rules, and voltage screening under a 33-bus radial-network surrogate. Fixed-test evaluation over five random seeds and 62 chronologically held-out test days shows that the proposed controller reduces total operating cost from 1003.66 to 686.31 k c.u. (31.6%) and unserved energy from 1743.25 to 1052.14 kWh (39.6%) relative to MPC-Lite, while reducing average decision time from 180.21 to 43.55 ms per step. In a separate safety-filter ablation, the filter reduced total cost from 912.47 to 686.31 k c.u., the hard-voltage violation rate from 25.31% to 19.46%, and the executed state-of-charge violation rate from 0.40% to 0.00%. These results indicate that the proposed framework supports reliable and efficient renewable-rich microgrid operation, facilitating renewable-energy integration and enhancing operational resilience. Full article

This study reports the synthesis and comprehensive characterization of a novel 5% cadmium-doped cerium oxide/reduced graphene oxide (5% Cd-CeO₂/rGO) nanocomposite for the enhanced visible-light-driven photocatalytic degradation of methyl orange (MO). The nanocomposite was prepared using a simple co-precipitation method followed by thermal reduction, which integrates the excellent electron-transport properties of reduced graphene oxide (rGO) with the oxygen-vacancy-rich characteristics of Cd-doped CeO₂, resulting in improved photocatalytic performance. The successful synthesis of the nanocomposite and the direct interaction between the rGO sheets and ultrafine CeO₂ nanoparticles were verified through structural and morphological analyses using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM). XPS results indicated an increase in the Ce³⁺ concentration and oxygen vacancy density after Cd doping and rGO incorporation, both of which play a crucial role in enhancing photocatalytic activity. Under visible-light irradiation, the 5% Cd-CeO₂/rGO nanocomposite exhibited substantially higher photocatalytic activity and methyl orange (MO) degradation efficiency than pristine CeO₂ and reduced graphene oxide (rGO). The improved photocatalytic performance demonstrates the beneficial role of combining metal-ion doping with conductive carbon supports to facilitate charge separation and electron transport in semiconductor photocatalysts. The developed nanocomposite also shows promising potential for the design of next-generation semiconductor-based materials for photocatalytic, energy conversion, and optoelectronic applications. Full article

Extremely fast charging (XFC) of high-energy-density lithium-ion batteries is fundamentally constrained by the intrinsic waveform characteristics of conventional variable-current profiles (VCPs), limiting further reductions in charging time while maintaining electro-thermal safety. In the present study, a computational electro-thermally constrained optimization framework is developed in which a square-wave VCP is reformulated using a finite Fourier series to improve XFC performance. An electro-thermal numerical model is employed to evaluate the charging behavior of the resulting Fourier series-based square wave (F-square wave) with the number of harmonic terms ranging from N = 1 to 100. The optimal charging performance is achieved at N = 10, reducing the charging time from 940 to 878 s (6.6%) and satisfying the U.S. DOE 15-min XFC target (900 s). The performance enhancement originates from two complementary effects: the Gibbs overshoot, which locally increases the charging current near the allowable current limit, and the finite-series approximation, which smooths the current transition before and after the waveform discontinuity. Rather than treating the Gibbs overshoot associated with Fourier approximation as an undesirable numerical artifact, this study demonstrates that it can be computationally exploited as a controlled perturbation to accelerate charging while maintaining electro-thermal safety. Although the Fourier perturbation slightly increases the terminal voltage risk near the waveform discontinuity, all electrical and thermal constraints remain satisfied throughout the charging process. These findings demonstrate that finite Fourier perturbation provides an effective computational design strategy for overcoming the intrinsic waveform limitations of discontinuous charging profiles and advancing electro-thermally constrained XFC of lithium-ion batteries. Full article

BiOF has emerged as a promising functional material for photocatalysis, electrochemical energy storage, and ion adsorption due to its unique layered structure, excellent chemical stability, and tunable electronic properties. Density functional theory (DFT) calculations provide in-depth theoretical insights into the crystal structure, intrinsic defects, doping modification, and heterostructure construction of BiOF. This review systematically summarizes the recent DFT research progress of BiOF systems. Computational results reveal the lattice characteristics, bandgap features, built-in electric field distribution and facet anisotropy of BiOF, and highlight the critical influence of Bi semicore states on structural relaxation and electronic modulation. Defect engineering of bismuth and oxygen vacancies can effectively optimize band structure, accelerate carrier separation and improve catalytic performance. Cation and anion doping introduce impurity energy levels to narrow the bandgap and broaden the visible-light response range. Various BiOF-based heterostructures with different band alignment modes are analyzed, and the interfacial built-in electric field dominates charge separation, while excessive formation energy and unfavorable charge transfer still restrict material optimization. This work provides a systematic theoretical reference for the rational design and performance improvement of high-efficiency BiOF-based materials. Full article