Humanity is confronting significant environmental issues due to rising energy demands and the unchecked use of fossil fuels. Thus, the strategic employment of sustainable and environmentally friendly energy sources is becoming increasingly vital. Additionally, addressing challenges, such as low reactivity, suboptimal energy efficiency, and restricted selectivity, requires the development of innovative catalysts. Two-dimensional (2D) covalent organic frameworks (COFs), known for their limitless structural versatility, are proving to be important materials in energy conversion applications. The exceptional properties of 2D COFs, including an organized arrangement resulting in well-defined active sites and π-π stacking interactions, enable breakthroughs in sustainable energy conversion applications. In this study, we comprehensively investigate universal synthesis methods and specific techniques, such as membrane-based deposition, liquid-phase intercalation, and polymerization. Furthermore, we demonstrate energy-conversion applications of 2D COFs as eco-friendly catalysts for electrochemical processes to promote sustainability and scalability by utilizing them in the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and carbon dioxide reduction reaction. Additionally, we will explore methods for analyzing the physicochemical properties of precisely fabricated 2D COFs. Despite extensive research pertaining to 2D COFs, their practical industrial applications remain limited. Therefore, we propose various perspectives, including enhancing performance, improving synthesis methods, developing binder-free catalysts, expanding catalyst functionality, and advancing full-cell research, to achieve complete industrialization by leveraging their potential.

Although lithium-sulfur (Li-S) batteries have a high theoretical energy density, their practical applications are limited by rapid capacity fading and poor cycling stability due to the dissolution of high-order polysulfides in electrolytes and the sluggish kinetics of the solid-state Li₂S₂/Li₂S redox reaction. Herein, a polysulfide sorbent and redox reaction catalytic promoter, Au quantum dots (Au QDs)-decorated MXene nanosheet, is designed by proposing defect-induced-reduced Ti₃C₂T_x (MXene) to improve the performance of Li-S batteries. The polar surface functional groups and high electronic conductivity of the MXene boost the conversion of sulfur/polysulfides and restrict the dissolution of the polysulfide shuttle. The Au QDs catalyst reduces the conversion reaction activation energy to achieve rapid solid-state Li₂S₂/Li₂S reaction kinetics. Due to the adsorption-catalysis synergistic effect between MXene and Au QDs, an initial discharge capacity of 1,500 mA h g^-1 is obtained, corresponding to a sulfur utilization of 90%. A Li-S battery based on the Au QDs@MXene-decorated separator exhibits a capacity retention rate of 71.0% for 300 cycles at 1 C.

Dual-ion batteries (DIBs) have attracted extensive attention and investigations due to their inherent wide operating voltage and environmental friendliness. Nevertheless, the vast majority of DIBs employ metal-based anode active materials or electrolytes, which are relatively costly and unsustainable. Moreover, the utilization of binders and current collectors in the preparation of cathodes and anodes reduces the energy density to a certain extent, which weakens the advantages of DIBs. Here, we synthesized three types of binder-free nano-embroidered spherical polyimide anode materials composed entirely of renewable elements, paired with pure ionic liquid electrolyte without metal elements and flexible self-supporting independent graphite paper cathode without current collector, to construct a class of totally metal and binder-free DIBs. It significantly improves specific discharge capacity, energy density, cyclic stability, and fast charging performance while remarkably reducing costs and self-discharge rate. Additionally, we overcame the drawbacks of conventional synthesis methods and innovatively prepared nanoscale polyimide materials by a green and facile hydrothermal method, which effectively minimizes synthesis costs and avoids risks. This novel battery system design strategy will promote the advancement of low-cost, high-performance DIBs and could be a promising candidate for large-scale energy storage applications.

The poly (phenylene sulfide) (PPS) fiber membrane is composed of interwoven fibers, with a three-dimensional porous structure. The three-dimensional porous structure makes PPS fiber membranes have high porosity and large specific surface area, which stands out in the field of membrane separation. A PPS fiber is a high-performance fiber with excellent chemical and thermal stability. These characteristics allow PPS fiber membranes to be used in harsh membrane separation environments such as strong acids, alkalis, and high temperatures. However, the corrosion resistance and high-temperature stability of PPS fibers also make the preparation of PPS fibers and their membranes challenging. In this paper, the preparation method is summarized, including two direct methods to make a PPS fiber membrane: melt-blown spinning and melt electrostatic spinning, and two indirect methods: wet papermaking and weaving. Additionally, the applications of PPS fiber membranes are summarized in detail in energy and environmental fields, such as lithium-ion batteries, alkaline water electrolysis, air filtrations, chemical catalyst substrates, and oil-water separations. This review provides an insightful understanding of PPS fiber membrane preparation methods and the interconnections between these preparation methods and specific applications, thus laying a solid foundation for further advancing the range of PPS fiber membrane applications.

Silicon nanowire anodes were investigated in lithium-metal cells using different electrolyte formulations based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide and N-trimethyl-N-butyl-ammonium bis(fluoro sulfonyl)imide ionic liquids. The lithium insertion process in the silicon anode was analyzed by cyclic voltammetry measurements, performed at different scan rates and for prolonged cycles, combined with impedance spectroscopy analysis. A galvanostatic charge-discharge cycling test was performed to analyze the electrochemical performances using different types of ionic liquids. A study of the Solid Electrolyte Interphase layer on the silicon nanowire electrode surface was carried out through X-ray photoelectron spectroscopy. In general, the silicon anodes in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide-based electrolytes show very good reversibility, reproducibility, and efficiency in the lithiation process, even at high scan rates, and exhibit a reversible capacity exceeding 1,000 mA h g^-1 after 2,000 charge-discharge cycles, corresponding to 46% of the initial value.

Exploring highly stable alloy-type anodes for rechargeable lithium batteries is urgent with the ever-increasing demands for high energy density batteries. The liquid metal (LM)-based anodes demonstrate great potential in advanced lithium-ion batteries due to their high energy densities and self-healing performance. However, its high surface tension leads to poor wettability towards the current collector and higher interfacial contact resistance. In this study, we developed a new free-standing LM-based anode LM-W10/Cu foil with good wettability and machinability by mixing high-melting-point tungsten (W) nanoparticles. It greatly improves the inherent defects of poor interfacial contact and lithium diffusion kinetics between the LM and current collectors, reduces the tedious and costly electrode manufacturing process, and regulates lithium deposition behaviors. And this metal mixing strategy has a negligible effect on the self-healing nature of LM. Symmetric cells of LM-W10/Cu foil anodes displayed a low overpotential (~13 mV) and cycled stably for more than 8,000 h (4,000 cycles) at 0.5 or 1 mA/cm²; full cells coupled with LiFePO₄ cathode showed a high capacity retention of 95.15% after 150 cycles.

Rising atmospheric CO₂ concentrations urgently call for advanced sustainable energy storage solutions, underlining the pivotal role of renewable energies. This perspective delves into the capabilities of redox flow batteries as potential grid storage contenders, highlighting their benefits over traditional lithium-ion batteries. While all-vanadium flow batteries have established themselves, concerns about vanadium availability have steered interest toward Organic Flow Batteries. The multifaceted nature of organic materials calls for an integrated approach combining artificial intelligence, robotics, and material science to enhance battery efficacy. The union of artificial intelligence and robotics expedites the research and development trajectory, encompassing everything from data assimilation to continuous refinement. With the burgeoning metaverse, a groundbreaking avenue for collaborative research emerges, potentially revolutionizing flow battery research and catalyzing the progression towards sustainable energy resolutions.

Ammonia has been used in a wide variety of applications, and with the recent interest in hydrogen energy as a green energy source, it is emerging as a cost-effective, high-density hydrogen carrier due to its three hydrogen atoms. Currently, ammonia is produced by the Haber-Bosch method at high temperatures and pressure, which is energy-intensive and emits large amounts of carbon dioxide. As a viable alternative, the electrochemical conversion of nitrate to ammonia has emerged as an efficient and eco-friendly synthesis method. To encourage further exploration in this field, this review offers insights into utilizing two-dimensional materials as electrochemical catalysts, focusing on designs that exploit defects for nitrate reduction to ammonia.

Solar-driven interfacial evaporation (SIE) is an emerging research topic that is gaining attention due to its potential in addressing global water scarcity issues. This review provides a comprehensive overview of base materials, recent innovations in photothermal materials and the design of evaporators for effective water desalination and purification. The recent development of SIE is meticulously discussed, providing a deep understanding of the key performance indicators and state-of-the-art materials. Additionally, this review examines novel strategies that have been reported in the literature for enhancing the efficiency and scalability of SIE systems. These strategies involve using photothermal materials and exploring innovative device configurations. Finally, we discuss the existing challenges and future research directions, emphasizing the potential of SIE in addressing global water scarcity and contributing to a sustainable future.

Solid-state batteries have garnered attention due to their potentiality for increasing energy density and enhanced safety. One of the most promising solid electrolytes is garnet-type Li₇La₃Zr₂O₁₂ (LLZO) ceramic electrolyte because of its high conductivity and ease of manufacture in ambient air. The complex gas-liquid-solid sintering mechanism makes it difficult to prepare LLZO with excellent performance and high consistency. In this study, an in-situ Li₂O-atmosphere assisted solvent-free route is developed for producing the LLZO ceramics. First, the lithium-rich additive Li₆Zr₂O₇ (LiZO) is applied to in-situ supply Li₂O atmosphere at grain boundaries, where its decomposition products (Li₂ZrO₃) build the bridge between the grain boundaries. Second, comparisons were studied between the effects of dry and wet routes on the crystallinity, surface contamination, and particle size of calcined powders and sintered ceramics. Third, by analyzing the grain boundary composition and the evolution of ceramic microstructure, the impacts of dry and wet routes and lithium-rich additive LiZO on the ceramic sintering process were studied in detail to elucidate the sintering behavior and mechanism. Lastly, exemplary Nb-doped LLZO pellets with 2 wt% LiZO additives sintered at 1,300 °C × 1 min deliver Li⁺ conductivities of 8.39 × 10^-4 S cm^-1 at 25 °C, relative densities of 96.8%, and ultra-high consistency. It is believed that our route sheds light on preparing high-performance LLZO ceramics for solid-state batteries.

Multivalent-ion batteries, as promising alternative or supplementary technologies to lithium-ion batteries, have increasingly attracted attention recently. Various advanced materials have been presented to pursue potential breakthroughs in energy and power. Among them, vanadium (V)-based materials benefiting from abundant resources, various polymorphs and valences, especially most with large interlayer spacings, are good candidates for multivalent-ion storage. However, limited by multiple inherent issues, e.g., strong electrostatic interactions, poor electronic conductivity, structure collapse or materials dissolution under battery operation, etc., various strategies have sprung many advanced materials and applications and also brought about new challenges that are in urgent need to clarify and summarize. Hence, advanced V-based compounds developed for multivalent-ion storage in the past few years are selectively summarized and systematically analyzed, including vanadium oxides and sulfides, vanadates, and V-based MXenes and phosphates. Not only crystal structures and electrochemical properties but also mainstream ion storage mechanisms are critically reviewed. Through analyzing the challenges accompanying multivalent-ion storage, potential opportunities are anticipated.

Electrochemical conversion of carbon dioxide (CO₂) into high-value chemicals and fuels driven by electricity derived from renewable energy has been recognized as a promising strategy to achieve carbon neutrality and create sustainable energy. Particularly from the viewpoint of the product values and the economic viability, selective CO₂ reduction to formic acid/formate has shown great promise. Palladium (Pd) has been demonstrated as the only metal that can produce formic acid/formate perfectly near the equilibrium potential; yet, it still suffers from CO poisoning, poor stability and competitive CO pathway at high overpotentials. Herein, recent progress of Pd-based electrocatalysts for selective CO₂ electroreduction and their mechanistic understanding are reviewed. First, the fundamentals of electrochemical CO₂ reduction and the reaction pathway of formic acid/formate on Pd are presented. Then, recent advances in the rational design and nanoscale engineering strategies of Pd-based electrocatalysts for further improving CO₂ reduction activity and selectivity to formic acid/formate product, including size control, morphology and shape control, alloying, heteroatom doping, surface-strain engineering, and phase control, are discussed from the perspectives of both experimental and computational aspects. Finally, we discuss the pertinent challenges and describe the future prospects and opportunities in terms of the development of electrocatalysts, electrolyzers and characterization techniques in this research field.

Ultrathin lithium (Li) metal foils with controllable capacity could realize high-specific-energy batteries; however, the pulverization of Li metal foils due to its extreme volume change results in rapid active Li loss and capacity fading. Here, we report a strategy to stabilize ultrathin Li metal anode via in-situ transferring Li from ultrathin Li foil into a well-designed three-dimensional gradient host during a cycling process. A three-dimensional carbon fiber with gradient distribution of Ag nanoparticles is placed on the ultrathin Li foil in advance and acts as a Li reservoir, guiding Li deposition into its interior and thus alleviating the volume change of ultrathin Li foil anodes. Hence, a high reversibility of Li metal is achieved and Li pulverization is suppressed, which can be witnessed by a long cyclic life in the symmetric cells. The proposed method offers a versatile and facile approach for protecting ultrathin Li metal anodes, which will boost their commercial application process.