As the core functional unit of the flow battery system, the surface and interface microenvironment of carbon electrode materials determine the electrochemical polarization behavior and energy storage performance. From the perspectives of microstructural regulation and electronic structure modulation, this review systematically examines carbon electrode surface/interface modification strategies and their mechanisms for enhancing flow battery performance. It systematically discusses how microstructural regulation and electronic structure modulation can effectively optimize mass transport kinetics, charge transfer efficiency, and electrocatalytic activity, consequently mitigating electrode polarization. Particular emphasis is placed on unveiling the underlying structure–performance relationships and the structure–function interplay between the electrode microenvironments and their resultant electrochemical properties. Furthermore, advanced characterization techniques, including synchrotron radiation, X-ray absorption spectroscopy, in situ Raman spectroscopy, and first-principles calculations, are summarized to elucidate the dynamic evolution of carbon electrodes. These methods provide crucial insights into how surface chemical modifications reconstruct electronic structures and active sites, leading to suppressed concentration and electrochemical polarization. Building on recent progress in atomically dispersed metal electrocatalysts, we also propose the rational design of single-atom catalyst-modified carbon electrodes. Moreover, synergistic strategies integrating high-throughput computation with machine learning are envisioned to establish multidimensional predictive models based on band structure, adsorption energy, and reaction pathways, thereby addressing the bottlenecks of metal utilization efficiency and structure–performance correlation. Overall, this review delivers a multidimensional theoretical framework and technological roadmap for the rational design and practical deployment of high-performance carbon electrodes in next-generation flow batteries.

As an important material in the process of unconventional oil and gas production, proppant plays a vital role in improving the recovery rate of unconventional oil and gas. With the development of proppant technology, multifunctional proppants have been designed and prepared to meet various needs. Understanding the mechanism of proppant action and migration patterns during unconventional oil and gas production can also provide more targeted guidance for proppant development. This paper introduces the classification, functions and existing technologies of proppants. After dividing proppants into common proppants and new proppants, experimental and simulation studies on proppant migration and placement rules are reviewed. At present, proppants at home and abroad are mainly developing in the direction of low density, high strength, high conductivity and multi-functionality, and combined with the experimental data of proppant migration and placement to improve the simulation study of Euler-Euler, Euler-Lagrangian and Lagrangian-Lagrangian model is also an important development direction for the exploration of proppant migration rules in the future.

The performance of iron-chromium redox flow batteries is significantly influenced by the electrochemical activity of chromium and iron ions, with a particular emphasis on the reactivity of chromium. However, the impact of the chemical properties of chromium ions on the efficiency of electrochemical reactions remains largely unexplored. In this study, we introduced PbCl₂ into the electrolyte and achieved in-situ electrodeposition of the lead-based catalyst. Our findings indicate that the incorporation of lead ions effectively enhances the chromium half-reaction while inhibiting hydrogen evolution. Experimental analyses and molecular dynamics simulations reveal that PbCl₂ does not significantly affect the electrochemical performance of the electrolyte, its influence is mainly due to the electrochemical deposition on the electrode surface. The observed performance improvement is ascribed to the combined effects of Pb and Pb(ClO₃)₂, which catalyze the redox reaction of Cr³⁺/Cr²⁺. In situ differential electrochemical mass spectrometry monitoring of the hydrogen evolution signal demonstrates a clear inhibition of the hydrogen evolution reaction. Notably, the addition of 40 ​mM ​Pb²⁺ significantly reduces the overpotential of the reaction, allowing the energy efficiency of the battery to reach 83.90% at a current density of 140 ​mA/cm², which represents a 5.68% increase compared to the original electrolyte (78.22%). Furthermore, this configuration enables long-term stable operation over 400 cycles. This research presents an innovative approach to enhancing the performance of iron-chromium redox flow batteries, characterized by its simplicity and cost-effectiveness.

Single-atom catalysts (SACs) are considered as the most promising nonprecious metal alternatives for oxygen reduction reactions (ORR) in proton exchange membrane fuel cells because of their high atomic utilization and excellent catalytic performance. However, the inadequate activity and long-term stability of SACs under operational conditions significantly hinder their practical application. Therefore, this paper focuses on understanding the micro- and electronic structures that synergistically enable the activity and stability of oxygen reduction. It provides a comprehensive summary of the effects for improving the ORR catalytic activity and stability of SACs from a multilevel, multi-angle perspective, including macroscale adjustments to the overall catalyst structure, nanoscale optimization of the catalyst microstructure, and atomic-scale regulation of the active sites. Additionally, it emphasizes the importance of advanced simulation, computational methods, and characterization techniques in understanding the catalytic and degradation mechanisms of SACs during the ORR process. This review aims to provide a theoretical foundation for the synergistic catalytic mechanisms and long-term stable operation of catalytic sites in complex heterogeneous environments, thereby advancing research on low-cost, high-efficiency, and highly stable single-atom catalysts.

The electrolyte in the flow battery is the carrier of energy storage, however, there are few studies on electrolyte for iron-chromium redox flow batteries (ICRFB). The low utilization rate and rapid capacity decay of ICRFB electrolyte have always been a challenging problem. Herein, the effect of Fe/Cr molar ratio, and concentration of HCl on the performance of ICRFBs at high current density (140 mA cm⁻²) are investigated. The average energy efficiency of the optimal electrolyte (1.25 M FeCl₂, 1.50 M CrCl₃, 3.0 M HCl) increases by 5.99% in the first 20 cycles, and the discharge capacity increases by 15.72% in the first cycle compared to the original commercial electrolyte (1.0 M FeCl₂, 1.0 M CrCl₃, 3.0 M HCl). This electrolyte also shows a longer cycle life. In addition, the COMSOL simulation on the concentration change of electrolyte in ICRFB is proposed, the effect of physical properties on the electrolyte is further explained. Through the simulation and analysis of this complex system, researchers can better understand the performance of flow battery systems. It is important to consider various challenges and constraints that might be encountered in practical applications. This work effectively saves the cost of ICRFB and further provides data support for their engineering applications.

Synthesis of functional nanostructures with the least number of tests is paramount towards the propelling materials development. However, the synthesis method containing multivariable leads to high uncertainty, exhaustive attempts, and exorbitant manpower costs. Machine learning (ML) burgeons and provokes an interest in rationally designing and synthesizing materials. Here, we collect the dataset of nano-functional materials carbon dots (CDs) on synthetic parameters and optical properties. ML is applied to assist the synthesis process to enhance photoluminescence quantum yield (QY) by building the methodology named active adaptive method (AAM), including the model selection, max points screen, and experimental verification. An interactive iteration strategy is the first time considered in AAM with the constant acquisition of the furnished data by itself to perfect the model. CDs exhibit a strong red emission with QY up to 23.3% and enhancement of around 200% compared with the pristine value obtained through the AAM guidance. Furthermore, the guided CDs are applied as metal ions probes for Co²⁺ and Fe³⁺, with a concentration range of 0–120 and 0–150 μM, and their detection limits are 1.17 and 0.06 μM. Moreover, we also apply CDs for dental diagnosis and treatment using excellent optical ability. It can effectively detect early caries and treat mineralization combined with gel. The study shows that the error of experiment verification gradually decreases and QY improves double with the effective feedback loops by AAM, suggesting the great potential of utilizing ML to guide the synthesis of novel materials. Finally, the code is open-source and provided to be referenced for further investigation on the novel inorganic material prediction.

Iron-chromium redox flow battery (ICRFB) is an electrochemical energy storage technology that plays a vital role in dealing with the problems of discontinuity and instability of massive new energy generation and improving the acceptance capacity of the power grid. Carbon cloth electrode (CC) is the main site where the electrochemical reaction occurs, which always suffers from the disadvantages of poor electrochemical reactivity. A new N-B co-doped co-regulation Ti composite CC electrode (T-B-CC) is firstly generated and applied to ICRFB, where the REDOX reaction can be promoted significantly owing to the plentiful active sites generated on the modified electrode. As contrasted with ICRFB with normal CC electrode, after 50 battery charge/discharge cycles, the discharge capacity (1,990.3 ​mAh vs 1,155.8 ​mAh) and electrolyte utilization (61.88% vs 35.94%) of ICRFB with CC electrode (T-B-CC) are significantly improved. Furthermore, the energy efficiency (EE) is maintained at about 82.7% under 50 cycles, which is 9.3% higher than that of the pristine electrically assembled cells. The co-modulation of heteroatom doping and the introduction of Ti catalysts is a simple and easy method to improve the dynamics of the Cr³⁺/Cr²⁺ and Fe³⁺/Fe²⁺ reactions, enhancing the performance of ICRFBs.

Iron-chromium redox flow batteries (ICRFBs) have emerged as promising energy storage devices due to their safety, environmental protection, and reliable performance. The carbon cloth (CC), often used in ICRFBs as the electrode, provides a suitable platform for electrochemical processes owing to its high surface area and interconnected porous structure. However, the CC electrodes have issues, such as, insufficient electron transfer performance, which limits their industrial application. Here, we employed silicic acid etching to carve dense nano-porous structures on the surface of CC electrodes based on the favorable design of ICRFBs and the fundamental principles of electrode polarization losses. As a result, we developed a multifunctional carbon cloth electrode with abundant vacancies, notably enhancing the performance of the battery. The fabricated electrode showcased a wealth of defect sites and superior electronic transport properties, offering an extensive and effective reaction area for rapidly flowing electrolytes. With an electrode compression ratio of 40% and the highest current density in ICRFBs so far (140 mA·cm⁻²), the battery achieved the average energy efficiency of 81.3%, 11.24% enhancement over the previously published work. Furthermore, throughout 100 charge–discharge cycles, the average energy efficiency degradation was negligible (~ 0.04%), which has the potential to become the most promising candidate for large-scale and long-term electrochemical energy storage applications.

With the deployment of renewable energy and the increasing demand for power grid modernization, redox flow battery has attracted a lot of research interest in recent years. Among the available energy storage technologies, the redox flow battery is considered the most promising candidate battery due to its unlimited capacity, design flexibility, and safety. In this review, we summarize the latest progress and improvement strategies of common inorganic redox flow batteries, such as vanadium redox flow batteries, iron-chromium redox flow batteries, and zinc-based redox flow batteries, including electrolyte, membrane, electrode, structure design, etc. In addition, we introduce the latest progress in aqueous and non-aqueous organic redox flow batteries. We also focus on the modification mechanism, optimization design, improvement strategy, and modeling method of the redox flow battery reaction. Finally, this review presents a brief summary, challenges, and perspectives of the redox flow battery.

The in situ mining technology is applied to the exploitation of medium- and low-maturity shale oil, which can use heaters to warm up the oil shale formations and pyrolyze the kerogen. Due to the low thermal conductivity of oil shale, electric heaters need extra equipment to improve heat transfer efficiency. In this study, a thermally conductive proppant is fabricated by coating epoxy-resin and graphite on ceramic proppants for the first time, which could support the fracturing crack and transfer heat. The thermal conduction property of epoxy-resin and graphite coated proppants (EGPs) is 245% higher than that of uncoated proppants, which can transfer more heat to the oil shale formation and accelerate the conversion of kerogen. The adhesive property of EGPs is improved by 47.9% under the load force of 1500 nN, which prolongs the time for the fracture to close. In summary, this novel proppant is expected to assist in-situ mining technology in the production of medium and low-maturity shale oil.