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Closed-loop manufacturing for sustainable perovskite photovoltaics
No full textPerovskite solar cells (PSCs) are emerging as a particularly promising technology to enhance the world’s renewable energy generation capacity. As PSCs are transitioning from research to industrial-scale production, there is an important opportunity to establish sustainable manufacturing pathways. Here, we present a closed-loop framework for the development of environmentally sustainable PSCs and highlight strategies to achieve this vision. First, we analyse the sourcing of raw materials and compare two established PSC fabrication techniques, vapour-phase deposition and solution processing, evaluating their respective advantages and limitations in terms of economic feasibility and environmental impact. Second, we examine solution processing methods, focusing on solvent system design for the preparation of high-quality perovskite films and on the use of non-hazardous or less-hazardous solvents. Third, we examine potential lead-release concerns during PSC operation and discuss approaches to minimize associated environmental risks. Fourth, we summarize effective recycling methods for main PSC components to support a circular production model. Finally, we identify key challenges and outline future research directions to achieve fully sustainable, closed-loop PSC technologies.</p
Interphase tailoring via fluorophenyl-boron integration for high-voltage LiCoO<sub>2</sub> operation
No full textAlmost all commercial lithium-ion batteries (LIBs) with LiCoO2 (LCO) as cathode material are cycled from 3.0 to 4.2 V and their actual specific capacity just ranges from 140 to 160 mA h g−1, which is much lower than the theoretical specific capacity of LCO of 274 mA h g−1. To further improve the actual specific capacity of LCO, elevating the upper limit of its working voltage is necessary. However, as the upper limit of its working voltage is elevated to 4.5 V or higher, the LCO crystal will undergo severe irreversible phase transition, and the oxidization decomposition of electrolyte on the cathode's surface will exacerbate, which will severely reduce the cycling lifespan of batteries, hindering the actual application of high voltage LCO. In this work, we find that 3,5-difluorophenylboronic acid pinacol ester (35-DAPE) is an effective cathode electrolyte interphase (CEI)-forming additive, which can form a robust and stable CEI layer rich in fluorophenyl-groups and B–F/B–O bonds on the surface of LCO cathode, inhibiting the dissolution of cobalt ions and maintain the structural stability of LCO crystal over cycles. The graphite\\LCO pouch cells in a voltage range of 3.0–4.5 V with 35-DAPE display a capacity retention rate of 91.1 % after 150 cycles at room temperature, compared to that of 2.4 % in baseline electrolyte. Besides, rate performance at room temperature and discharging performance at low temperatures of graphite\\LCO pouch cells can also be observed with an improvement after the introduction of 35-DAPE. In addition, this work has explained the decomposition mechanism of 35-DAPE and how its products improve the electrochemical performance of graphite\\LCO pouch cells in detail, which not only advances the actual application of fluorophenylboronic acid pinacol ester additive in high voltage LIBs but also provides valuable insights for the design of functional electrolyte additives.</p
An image steganography algorithm using selective timestep embedding and diffusion model
No full textGenerative steganography has emerged as a promising scheme for enhancing the security of covert communication. However, existing diffusion-model-based approaches primarily utilize the model as a static generator or embed secret data exclusively at the initial noise input, failing to exploit the dynamics intrinsic to the denoising process. To address this limitation, an image steganography algorithm is presented using selective timestep embedding and diffusion model, named ImSA. Unlike conventional methods, ImSA introduces a plaintext related mechanism to select the optimal timestep, embedding secret information into the frequency domain of the intermediate latent variables. Specifically, the plain image is encrypted via a hyperchaotic system into noise-like sequence and subsequently embedded into the high-frequency wavelet subband at the selected timestep. Furthermore, the diffusion model is retrained to adapt to the distribution of latent variables containing the secret data. Compared with current generative steganography methods, the contributions of ImSA are: (1) The imperceptibility and security can be improved by dynamically selecting the specific timestep embedding; (2) The high-capacity information embedding and high-quality images generation can be achieved by frequency-domain embedding; (3) Minimizes disruption to the generative process by converting the plain image into a noise-like cipher. Moreover, experimental results demonstrate a 2.0 bpp embedding capacity with high generation quality, robust extraction quality (PSNR with 38 dB) and strong security performance (Probability of Error with 0.51)
Large area ternary TiO<sub>2</sub>/CdS/g-C<sub>3</sub>N<sub>4</sub> photoanode for hydrogen evolution by photoelectrochemical water splitting
No full textPhotoelectrochemical (PEC) water splitting is a key technology for sustainable hydrogen production, yet most studies focus on small-scale photoelectrodes. While some have developed large-area photoelectrodes, they primarily use single-material systems rather than heterojunction structures. Here, we present a large-area heterojunction-based photoanode with an optimized design for improved performance and scalability. Optimization begins at small scale (1 cm2) using a synergistic combination of TiO2/CdS/g-C3N4 ternary heterojunction and mesoporous architecture strategies. CdS enables substantial charge generation through efficient light absorption and separation, while integration of TiO2 and g-C3N4 form type-II heterojunction that promotes directional charge transfer. Mesoporous TiO2 scaffold further boosts the PEC performance by facilitating CdS deposition, where an optimized four-layer thickness balances light absorption and minimizes recombination losses. The photoanode achieves a photocurrent density of 2.38 mA/cm2 at 1.23 VRHE and an applied bias photon-to-current efficiency of 1.46 %. Scaling up to 16 cm2 yields a high photocurrent of 21.3 mA, corresponding to 56 % of the photocurrent density of the best-performing 1 cm2 photoanode. This is enabled by employing cost-effective dynamic dispensing method for depositing mesoporous TiO2, which in turn allows uniform CdS growth. The outcome of this work provides a valuable framework for advancing large-scale PEC technology toward commercial applications.</p
Towards a critical study of temporalities in sustainability transitions: speed, duration, acceleration, and timescapes
No full textAccelerating sustainability transitions is essential for tackling complex sustainability challenges, particularly in light of the ambitious climate targets set by the 2015 Paris Agreement. This chapter explores the multifaceted relationship between time and sociotechnical change within sustainability transitions, highlighting the urgent need for immediate action across energy systems, agriculture, and manufacturing to achieve net-zero emissions by 2050. The analysis demonstrates that accelerating transitions not only addresses climate change but also fosters innovation, social equity, and economic resilience. However, the implications of time—characterised by pace, speed, and acceleration—demand critical examination, as they can lead to unequal resource allocation and the marginalisation of vulnerable populations. The chapter discusses how different stakeholders advocate for varying timescales and technologies based on their interests, underscoring the political nature of sustainability transitions. It also introduces the concept of timescapes, which reflects the dynamic interplay of temporal dimensions that influence transition processes. Furthermore, the chapter reviews historical energy transitions to illustrate the complexities of speed, duration, and acceleration, emphasising the need for interdisciplinary approaches to understand these temporalities. By addressing the political underpinnings and social dynamics of sustainability transitions, the chapter aims to foster transparency, equity, and justice in climate action. Future research directions are proposed, focusing on the integration of diverse methodologies and the critical examination of temporal frameworks within sustainability transition studies, ultimately contributing to more effective and inclusive policies for sustainable futures
Local scour mechanism around offshore wind turbine monopile under current and combined current-wave flow using CFD-DEM method
No full textThe mesoscale mechanism of local scour around monopiles under combined wave and current conditions remains unclear. In this study, a coupling CFD-DEM method that incorporates two-phase flow is used to simulate local scour around monopiles under different combined wave-current conditions. A total of five cases are simulated and results are validated by comparison with existing experimental data and empirical relationships. The local scour mechanism around monopile is investigated from several perspectives, including scour process, scour pit morphology, flow field characteristics, fluid forces on particles and particle motion. The results reveal that the flow velocity, the fluid forces on particles and the seepage field within the particle bed exhibit periodic variations with wave propagation under the combined wave and current conditions, contrasting with the current-only condition. Additionally, the wave-induced seepage and increased flow velocity generate a vortex at the upstream side of the pile, which advances downstream with wave propagation. Throughout one wave period, the increased flow velocity and the upstream vortex contribute significantly to the scour process and particle forces, leading to a phenomenon termed “repeated backfill and scour”. As the combined wave–current parameter Ucw and the Keulegan–Carpenter (KC) number increase, both overall flow intensity and the strength of the upstream vortex increase, resulting in a deeper scouring depth and a longer duration to reach equilibrium. This study provides new insights into the local scour behavior around monopiles under combined wave and current conditions.</p
A Novel High-Order Shock-Capturing Limiter for RKDG Method on Unstructured Meshes via TENO Selection Strategies
No full textThere is a rapidly growing need for high-order numerical schemes on unstructured meshes in the numerical simulation of compressible flows. However, numerous barriers exist to achieve the desired high-order properties on unstructured meshes. The traditional finite-difference method is inadequate for complex unstructured meshes, whereas the finite-volume method introduces additional complexities, e.g., too large stencil size with too many neighboring cells for high-order reconstruction. The Runge–Kutta Discontinuous Galerkin (RKDG) method possesses inherent advantages for unstructured meshes, since it can ensure the high-order property regardless of the type of mesh within a compact stencil. On the other hand, the main weakness of the original RKDG method is their inability to capture discontinuities without artificial numerical oscillations. To tackle this issue, the troubled cell indicator and the slope limiter are integrated with the RKDG method to capture physical discontinuities, where the slope limiter modifies the numerical solutions of the troubled cells detected by the troubled cell indicator. In this work, we propose a new troubled cell indicator and a new limiter based on Targeted Essentially Non-Oscillatory (TENO) schemes for unstructured meshes. The new TENO troubled cell indicator can be applied to unstructured meshes with the compact property and ability to detect troubled cells. For each interface of the targeted troubled cells, the new TENO limiter is utilized to select a smooth numerical solution between the troubled cell and its immediate neighboring cell. Then, a novel weighting strategy is proposed to obtain the final reconstructed numerical solution from the candidate numerical solutions at each interface. It is worth noting that the conventional weighting strategy computes the final reconstructed numerical solution based on the area of corresponding neighboring cells, whereas the newly proposed weighting strategy determines the final reconstructed numerical solution regarding the smoothness of each candidate numerical solution from different interfaces rather than their areas. A set of benchmark cases, including strong shockwaves and a broad range of flow length scales, is simulated to illustrate the performance of the newly proposed limiter in comparison to the Weighted Essentially Non-Oscillatory (WENO) limiter on unstructured meshes. The newly proposed scheme significantly enhances the WENO limiter, exhibiting superior robustness and low-dissipation properties.<br/
Intent-based trust evaluation
No full textTrust relationships play a crucial role in various domains, such as social spam detection, retweet behavior analytics, and recommendation systems. Trust is often implicit and difficult to observe directly in the real world, as it is driven by people's underlying intentions and motivations. Therefore, when evaluating trust, it is critical to analyze not only user behavior data but also the intentions behind these behaviors that lead to trust. Existing trust evaluation methods often neglect the underlying reasons behind connections, such as shared hobbies or belonging to the same community. Therefore, these methods cannot differentiate the genuine intentions that lead to trust, resulting in an inaccurate evaluation of hidden trust relationships. To address this issue, we propose a novel Intent-based model for Trust Evaluation (INTRUST). This model can distinguish the intent behind high-order information in social communities using hypergraphs. Initially, we used hyperedges to represent high-order correlations between user-to-item and user-to-user interactions. Then, we construct K intent prototypes, which serve as foundational elements to build trust. Furthermore, we distinguish K-independent intent subgraphs from these high order correlations. To enhance the generalization and robustness of the model, we employ self-supervised learning and construct contrastive views at the node-level, hyperedge-level, and node hyperedge-level. Extensive experiments on real-world datasets demonstrate that our model outperforms state-of-the-art approaches in terms of trust evaluation accuracy and efficiency.</p
Mitigating the Dominance of Channel Resistance in β-Ga<sub>2</sub>O<sub>3</sub> UMOSFETs via Cell Pitch Scaling
No full textThis letter presents a systematic investigation of cell pitch (Lcell) scaling from 10 μm down to 5 μm on the electrical characteristics of vertical β-Ga2O3 U-shaped trench gate MOSFETs (UMOSFETs), enabled by a self-aligned gate trench etching process. The analysis of the components of the specific on-resistance (Ron,sp) reveals a critical transition: as Lcell is scaled, the drift region resistance surpasses the channel resistance to become the dominant performance-limiting factor. The scaled device with a Lcell of 5 μm demonstrates the merits of this strategy, achieving a low Ron,sp of 8.7 mΩ·cm2 and a high breakdown voltage (Vbr) of 1002 V. These parameters yield a power figure of merit (PFOM) of 115 MW/cm2, which is the highest among all the reported vertical β-Ga2O3 MOSFETs based on current blocking layer up to date. These findings provide a physical roadmap for future optimization of vertical Ga2O3 power transistors, highlighting the importance of drift region engineering in addition to channel optimization.</p
Molecular Drivers of Electron-Donating Capacity in Dissolved Black Carbon from Nitrogen-Rich Pyrogenic Carbon
No full textDissolved black carbon (DBC) from nitrogen-rich feedstock-derived pyrogenic carbon may influence aquatic photochemistry and byproduct formation due to its electron-donating capacity (EDC). Yet, the molecular drivers of EDC remain unclear. Here, we developed an integrated analytical framework to characterize DBC leached from nitrogen-rich biochar pyrolyzed at 350, 450, and 550 °C (DBC350, DBC450, and DBC550) under simulated intermittent rainfall over 30 days. Through two-dimensional correlation spectroscopy (2D-COS) and Fourier transform ion cyclotron resonance mass spectrometry, we analyzed sequential responses and synergistic relationships of thousands of individual DBC molecules with various functional groups. The EDC increased with leaching time, particularly in DBC350, coinciding with a shift toward lower m/z, more unsaturated, and aromatic compounds. Spearman's analysis showed that EDC-related molecules were predominantly nitrogen-bearing (61-76%), highly unsaturated, and low-oxygen. Our 2D-COS analysis on EDC-related molecules and functional groups identified (hetero)aromatic structures as key EDC contributors. Tandem mass spectrometry and X-ray photoelectron spectroscopy further confirmed the prevalence of carboxylic, pyrrolic, and/or amide groups. Extended (hetero)aromatic structures contributed to the higher EDC in DBC350 than in DBC450 and DBC550. Our study offers the first molecular and functional group-level insight into EDC-related DBC compositions, with implications for biochar-related and postwildfire water quality management.</p