Metal–organic frameworks (MOFs) have emerged as a highly promising class of crystalline proton-conducting materials owing to their designable structures, tunable pore environments, and well-defined conduction pathways. In recent years, superprotonic conduction in MOFs has become a major research focus, as an increasing number of MOF systems have achieved exceptionally high proton conductivities (>10–2 S cm–1) with low activation energies. These advances indicate that superprotonic conduction arises from the cooperative interplay of abundant proton carriers, continuous hydrogen-bonding networks, and low-barrier conduction pathways. This review summarizes rational strategies to enhance proton conduction and highlights representative recent advances in superprotonic conduction in MOFs under both hydrated and anhydrous conditions, with the structure–property relationships underlying their outstanding performance discussed in detail. Finally, key challenges and future directions for the design of proton-conductive MOFs are presented.
Hydrogen production via photocatalytic water splitting offers a sustainable pathway to address global energy and environmental challenges. Among various photocatalysts, metal–organic frameworks (MOFs) have emerged as highly promising platforms owing to their structural tunability, well-defined porosity, and modular integration of light-harvesting and catalytic functionalities. However, precise identification of active sites at the atomic level and a clear understanding of structure–performance relationships remain significant challenges. This review critically examines recent advances in MOF-based systems, with a focus on elucidating structure–performance correlations and strategies to overcome thermodynamic and kinetic limitations. Key approaches, including linker engineering, node modulation, heterostructure construction and the development of conductive MOF derivatives are discussed. Furthermore, advanced characterization techniques are presented to elucidate charge carrier dynamics and underlying reaction pathways. Finally, remaining challenges related to overall water splitting, long-term stability, scalability, and standardized evaluation protocols are outlined, along with future research directions.
The development of artificial water oxidation catalysts (WOCs) represents a journey of structural and conceptual evolution. It began with bioinspired explorations of the Mn4CaO5 cluster in Photosystem II, establishing core principles of molecular design based on precise control of metal nuclearity and coordination environments, and has now advanced towards a new generation of catalysts centered on earth-abundant metals. Throughout this progression, strategies such as multinuclear cooperativity and metal-ligand interactions have enabled base-metal catalysts to rival and even surpass the performance benchmarks set by their noble counterparts. To bridge the molecular precision of homogeneous catalysts with the operational stability required for practical applications, interfacial engineering has become paramount. Hybrid molecular electrodes, constructed through immobilization strategies that include it-it stacking and covalent anchoring, have emerged as representative paradigms that bridge the molecular and material realms. This review systematically delineates this structural evolution pathway. By integrating biological inspiration, molecular design, and interfacial engineering, it outlines a clear blueprint for developing efficient and stable sustainable water oxidation technologies.
Water splitting to produce hydrogen is recognized as a green technology with significant potential to replace traditional non-renewable energy sources. Substantial progress has been made in the hydrogen evolution reaction (HER), with two-dimensional (2D) materials for both photocatalytic and electrocatalytic HER due to their unique structural features and favourable properties. Along with experimental materials design, the properties of the 2D materials have been complemented by computational methods such as density functional theory (DFT) over the past decade. However, these computational approaches face limitations in terms of time and cost efficiency. Consequently, data-driven approaches, particularly machine learning (ML), are emerging as powerful tools in materials science for identifying structure-activity relationships by learning from existing experimental and DFT calculation data. This review discusses the progress of 2D materials for hydrogen evolution, encompassing experimental advances, theoretical insights, and ML-assisted discovery. First, the fundamental principles of HER are examined, combining insights from photocatalysis and electrocatalysis. Next, an overview of 2D materials for HER is presented, including key challenges related to kinetics, stability, and scalability. Subsequently, ML strategies for 2D material discovery and screening are explored. Case studies on ML applications for various 2D photocatalysts and electrocatalysts, including graphene, g-C3N4, transition metal chalcogenides, MXenes, etc., are discussed. Finally, factors influencing large-scale applications and challenges associated with integrating materials science and ML approaches for HER are addressed.
Zinc-air batteries (ZABs) are promising candidates for sustainable energy storage due to their high theoretical energy density (1086 Wh kg-1), low cost, and environmental compatibility. However, their practical deployment is hindered by limited rechargeability, arising from electrolyte instability, Zn anode degradation, and sluggish oxygen redox kinetics. Conventional alkaline and near-neutral electrolytes suffer from issues such as carbonation, dendrite formation, parasitic reactions, and poor reaction kinetics, which restrict long-term cycling performance. This review focuses on emerging electrolyte strategies beyond conventional systems, with particular emphasis on water-in-salt electrolytes (WiSE) and peroxide-mediated reaction pathways. We provide a mechanistic perspective on how electrolyte structure governs Zn2+ solvation, interfacial behaviour, and oxygen reaction pathways, thereby influencing Zn reversibility and overall battery performance. In particular, we discuss how reduced water activity and modified solvation environments in WiSE can suppress parasitic reactions and alter reaction kinetics, while peroxide-based chemistries enable alternative two-electron pathways with improved energy efficiency. By critically comparing these approaches, we highlight key challenges including transport limitations, interfacial stability, and the discrepancy between apparent stability and true Zn reversibility under practical operating conditions. Finally, we outline future research directions toward integrating electrolyte design with realistic performance metrics to enable commercially viable, high-performance rechargeable ZABs.
MXenes is a new kind of 2D transition metal carbides and nitrides, that have captivated researchers for their potential to revolutionize electrochemical applications like energy storage (supercapacitors and batteries), conversion (HER and OER) and electrochemical sensing applications. This review explores their multifaceted applications, focusing on their role in electrochemical applications. This article explores alternative MXene design and synthesis techniques beyond HF etching, including in situ HF etching, molten salt methods, electrochemical etching and many other methods, emphasizing how these methods influence desired MXene structures. Focusing on energy storage applications, this review investigates recent developments in MXenebased electrodes to improve supercapacitor performance in various configurations such as symmetric, asymmetric, metal-ion capacitors and microsupercapacitors. Also, the review explores MXenes usage in batteries such as Li-ion, Li-S, Na-ion, and Zn-ion energy storage technologies. Moreover, the energy conversion in electrochemical water splitting applications, demonstrating the MXene's ability in the hydrogen and oxygen evolution reactions. Furthermore, the electrochemical sensing is the most and common electrochemical technique to identify the various biomolecules and metals in the water resources. We further discussed the challenges and solutions to attain the sustainable solution of MXenes.
Low-dimensional metal nanostructures have sparked tremendous research activity owing to their valuable applications for energy conversion and storage technologies. The energy-related functionalities and stabilities of metal nanostructures are strongly dependent on their surface properties, chemical bonding nature, and electronic and geometric characteristics. Consequently, the regulation of these features can play a pivotal role in enhancing the electrochemical and catalytic performances of metal nanostructures. As an emerging approach for developing highly efficient and robust metal nanostructured materials, exsolution has garnered increasing attention because it enables effective control and stabilization of metal nanoparticles within solid matrices. Moreover, tuning the exsolution conditions can induce phase transitions in the solid substrates, allowing for the expansion of application area from conventional solid oxide fuel cells to other energy-related fields, such as catalysis and batteries. This review highlights the unique merits of phase-tunable exsolution for exploring high-performance energy-functional materials, with an in-depth discussion of the key design factors that optimize their energy performance. A comprehensive survey of a wide range of exsolved hybrid materials was conducted depending on the synthesis methods, characterization tools, and application fields. Future research perspectives for designing and synthesizing high-performance exsolution materials are provided to offer inspiring insights for improving their functionalities, which is pivotal for diverse energy technologies.
Hydrogen production via polymer electrolyte membrane water electrolysis (PEMWE) is central to scalable green hydrogen. Single-atom catalysts (SACs) offer a route to maximize noble-metal utilization while enabling precise control of local electronic structures, but current literature remains fragmented across synthesis techniques, descriptor analyses, and durability evaluations. In this review, we outline the fundamental reaction mechanisms of SACs for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under acidic conditions, and systematically consolidate the key reaction and electronic-structure descriptors that correlate activity, reaction pathways, and durability. We then establish an anchoring-mechanism-centered analytical framework that categorizes the construction of acidic SACs into four mechanistically driven strategies, and explicitly maps each strategy to its characteristic coordination motifs, support chemistry, and stabilization principles. Next, we examine representative acidic HER and OER systems, highlighting how structural and coordination features, metal-support interactions, and multicenter cooperative effects collectively shape the local electronic structure of single-atom sites, thereby governing intrinsic kinetics and stability behavior. Finally, we summarize the major challenges in this field and propose several promising directions for future development. This review aims to provide a coherent analytical framework and practically oriented design guidelines for the rational construction of next-generation acidic SACs for water electrolysis.
Imidazole-based MOFs, by virtue of the Lewis basicity endowed by electron-rich N sites, the Lewis acidity provided by tunable metal nodes, and the excellent designability of their pore structures, are ideal platforms for achieving highly active and highly selective photo/electrocatalytic conversion of CO2. This review systematically summarizes the latest progress of imidazole-based MOFs (including ZIFs, BIFs, and HZIFs) in the CO2RR. In terms of construction strategies, the structure-activity relationships are systematically elucidated from two dimensions: ligand engineering (functional group modification, coordination mode regulation, and defect engineering) and metal active site design (single-metal sites and heterometallic synergistic/cascade catalysis). It further covers multiscale functionalization pathways such as compositing with functional materials, carrier loading, and the preparation of derived materials. Regarding mechanistic research, by integrating in situ experimental characterizations and DFT calculations, the microscopic mechanisms of CO2 adsorption, activation, and multi-electron reduction are deeply revealed. Furthermore, it introduces the emerging applications of machine learning in high-throughput catalyst screening and reverse structural design. Finally, targeting core bottlenecks such as insufficient intrinsic conductivity, lack of device integration, and relatively high scale-up costs, it proposes future research directions for multidimensional synergistic breakthroughs, with the hope of driving the practical application of imidazole-based MOFs in the context of carbon neutrality.
Electrochemical water splitting is a key technology for sustainable hydrogen production, yet its large-scale application is hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Noble-metal-based catalysts can effectively lower OER overpotentials, while their high cost, limited abundance, and durability issues motivate the development of alternative catalyst platforms. Metal-organic frameworks (MOFs) have emerged as a distinctive class of materials for OER catalysis because they integrate molecular-level coordination environments with extended porous architectures. Their modular metal nodes, tunable organic ligands, and defect-engineering capability enable precise regulation of local electronic structure, active-site density, and mass and charge transport. In addition, MOFs serve as structurally programmable precursors that can be transformed into catalytically active (oxy)hydroxides, oxides, and metal-carbon composites, allowing the transfer of well-defined coordination motifs into robust working catalysts. However, the immense compositional and structural diversity of MOF-based systems have caused empirical optimization inefficient. Artificial intelligence (AI) is therefore emerging as a complementary methodology that links synthesis, structure, and performance through data-driven machine learning. By combining physically informed descriptors with statistical models, AI-assisted approaches provide new opportunities to rationalize catalyst evolution and accelerate application-oriented discovery. This review summarizes recent advances in MOF-based and MOF-derived OER electrocatalysts, with an emphasis on structure-performance relationships and AI-guided design strategies. Current challenges and future directions toward practically deployable OER catalysts are discussed.
Metal-organic frameworks (MOFs) and their derived porous composites have garnered significant scientific attention due to their exceptional porosity, high specific surface area, and tunable composition. One-dimensional (1D) nanostructures, characterized by directional charge transport, high aspect ratios, and structural continuity, offer fundamental advantages in overcoming key limitations in conductivity, active site accessibility, and mechanical stability inherent to many energy materials. MOFs with their exceptional synthetic tunability serve as an ideal building block for such purpose-engineered 1D systems. Specifically, the hierarchical 1D assembly of nanoscale building blocks can establish interconnected conductive networks, enabling collective functionalities and performance enhancement beyond those of individual components. Therefore, 1D MOF-based assemblies and their derivatives have emerged as highly promising candidates for advanced energy conversion and storage applications. In this review, we systematically summarize recent advances in 1D MOF-based architectures, with a focus on compositional modulation, structural engineering, and assembly strategies (including self-assembly and template-assisted assembly) across molecular to macroscopic scales. Additionally, several important applications in electrochemical energy conversion and storage are illustrated. Finally, some challenges and future directions in this area are presented. We anticipate that this comprehensive review will provide valuable insights for the rational design and construction of unique 1D MOF-based assemblies and their derivatives, ultimately advancing their practical implementation in next-generation energy technologies.
Photocatalytic/electrocatalytic carbon dioxide reduction reaction (P/ECO2RR) enables conversion of CO2 into high-valued products such as ethylene (C2H4) and ethanol (C2H5OH), offering a viable pathway for carbon emission reduction while storing renewable energy in form of chemical energy, which holds significant strategic importance. Compared with conventional catalysts, metal-organic frameworks (MOFs) and their derivatives can be precisely engineered by employing different metal nodes and organic linkers. The pore size, chemical environment and electronic structure can be finely tuned to facilitate the adsorption and activation of CO2 molecules. As a result, MOFs have been considered as an ideal platform for P/ECO2RR. In this article, we summarized the recent works on conversion of CO2 to C2H4 and C2H5OH photo-/electrochemically catalyzed by MOFs and their derivatives. The current challenges and future opportunities for the MOF-based and MOF-derived catalysts for P/ECO2RR toward C2H4 and C2H5OH production were also discussed.
Pt-based intermetallic nanocatalysts are gaining increasing attention as durable and active oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs). The ordered atomic configuration of these catalysts strengthens interactions between Pt and alloying metals, tunes the electronic structure, and provides better stability under acidic operating conditions of PEMFCs. This review summarizes the thermodynamic and kinetic principles of nanoscale Pt alloy disorder-to-order transitions and provides a basis for rational synthesis. Advances in composition design, ranging from binary systems to ternary and high-entropy intermetallics (HEIs), are discussed, along with structural and interfacial strategies that enable nanoparticle (NP) size control and high metal loading. Morphology-controlled Pt-based intermetallic catalysts exposing specific facets and having characteristic dimensions are also highlighted. Finally, representative studies employing X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) are highlighted to illustrate key characterization approaches used to probe intermetallic nanocatalysts. These insights will help in developing Pt-based intermetallic catalysts with both high activity and durability for practical PEMFC applications.
Not only is carbon the fundamental substance of life, it also plays an extremely important role in modern industry and the environment. In this review, we adopt the concept of 'carbon nanoarchitectonics', focusing on how precise electronic structure control and scalable fabrication strategies enable the development of carbon-based catalysts for energy applications. In particular, this review summarizes extensive studies on carbon catalysts for the oxygen reduction reaction (ORR), a key reaction in many energy conversion devices, and discusses how these insights can guide the rational design of carbon catalysts. The first section summarizes methods for creating and controlling carbon materials from a structural fabrication perspective. This includes geometric effects, such as the impact of size and curvature; the design of hydrophobic and hydrophilic surface structures; and the fabrication of hierarchical structures, including morphology, pore structure, and heterostructure. We also discuss bottom-up nanocarbon synthesis as a challenge in nanographene synthesis based on organic chemistry. The second half of this review summarizes the latest research into understanding and controlling the properties of carbon materials. Regarding the electronic structure and reactivity of carbon materials, we discuss the reactivity and electronic states of nitrogen-doped (N-doped) graphitic carbons, the basic sites associated with pyridinic nitrogen (pyri-N), and the Landau level in the absence of an external magnetic field. The section also covers the coupled hydrogenation of pyri-N, the adsorption of oxygen, the activity degradation of N-doped carbon catalysts in the ORR, and non-chemical localization strategies via geometric defects. The conceptual framework of 'carbon nanoarchitectonics' is essential for developing innovative carbon catalysts that can contribute to climate change mitigation. The insights summarized in this review will stimulate further advances in carbon material research and support the realization of a truly sustainable energy society.
The advancement of nonaqueous magnesium metal batteries (MMBs) is critically impeded by severe interfacial instability at the Mg anode. The primary challenge stems from the high charge density of Mg2+ ions, which promotes the formation of tenacious solvation structures and a passivating solid electrolyte interphase (SEI). These phenomena jointly lead to sluggish Mg2+ desolvation kinetics and inhomogeneous, dendritic Mg deposition. To address this, this review systematically dissects these fundamental interfacial challenges. We thoroughly evaluate in situ and operando characterization techniques that elucidate the dynamic processes at the electrode-electrolyte interface. Building on these mechanistic insights, we present a comprehensive analysis of rational optimization strategies, focusing on electrolyte solvation structure modulation, artificial interphase engineering, and 3D anode architecture design. By bridging advanced diagnostic insights with strategic material design, this review aims to deepen the fundamental understanding of Mg anode interfacial chemistry and provide a clear roadmap for developing practical, high-performance MMBs.
The growing demand for wearable electronics and smart textiles has intensified research into flexible, miniaturized, high-performance, and safe energy storage devices. Lithium-sulfur (Li-S) batteries, with their high theoretical energy density supported by sulfur's multielectron chemistry and cost-effectiveness, are highly promising, yet they face critical bottlenecks. These challenges include low long-cycle capacity retention and inadequate cycling durability during bending. Conventional materials such as graphene and conductive polymers fall short in interface stability or scalable synthesis, failing to balance electrical conductivity with mechanical strength simultaneously. MXene emerges as a breakthrough, offering metal-grade conductivity, tunable surface chemistry, abundant functional groups, and exceptional mechanical resilience. Its layered structure not only anchors polysulfides but also withstands repeated deformations. This review systematically examines the design strategies for Li-S batteries that integrate flexibility, high energy density, and cycling stability. Firstly, synthesis, structure, properties, and analysis of advantages of MXene used in Li-S batteries are summarized. Subsequently, computational and simulation approaches are employed to analyze MXene's role in addressing shuttle effects and lithium dendrite growth. Applications of MXene-based materials in various components of flexible Li-S batteries are then discussed. Finally, insights are provided on challenges and future developments for MXene-based flexible Li-S batteries.
The electrochemical hydrogen evolution reaction (HER) is a critical technology in green hydrogen production and various industrial processes, characterized by dynamic interactions at the electrode surface, catalyst structure, reaction intermediates, and electrolyzer components. A comprehensive understanding of these factors is essential for elucidating the reaction mechanism and designing efficient electrocatalysts. This review examines the interaction between electrolytes and surface adsorbates, analyzes the associated challenges and opportunities in the HER process, and focuses on the three key interface effects that determine HER activity and stability: the electric field effect, the Marangoni effect, and the electrolyte-induced interface reconfiguration effect. Under industrial conditions, interactions within the catalyst layer can influence the binding energy of adsorbed intermediates. Furthermore, the local electric field determined by the zero-charge potential plays a key role in stabilizing polar adsorbates and regulating proton transfer. Structural rearrangement outside the catalyst layer, along with the Marangoni effect triggered by bubble dynamics, also increases energy barriers to the reaction process. By combining in-situ characterization techniques with multi-scale theoretical simulations, the coupling effects of these phenomena under high current density can be better understood, providing effective tools for real-time analysis of interface dynamics under operating conditions. Finally, based on a deep understanding of the interface microenvironment, strategies for optimizing HER catalysts are proposed, along with potential challenges and development prospects for interface engineering technology in large-scale applications.
Photocatalytic CO2 reduction (CO2RR) to high-value chemicals and fuels presents a promising yet challenging strategy for addressing energy and environmental crises. Despite considerable advances in producing C1 products, the selective synthesis of more desirable multi-carbon (C2+) compounds remains hindered by the kinetic and thermodynamic complexities of multi-electron/proton transfers and C-C coupling. Thus, in this review, we will summarize the advances in photocatalytic CO2 reduction to C2+ products in recent years. To overcome the kinetic and thermodynamic limitations, the review will emphasize the importance of synergistic catalytic strategies in designing efficient photocatalytic systems, including defect engineering, heterojunction construction, cocatalyst loading, and localized surface plasmon resonance (LSPR) effects. These strategies aim to enhance charge separation, increase surface electron density, stabilize key reaction intermediates, and lower the energy barrier for C-C coupling during CO2RR. Specifically, the mechanistic investigation into synergistic catalysis will reveal its critical role in directing photocatalytic CO2 reduction toward various C2+ products, highlighting that synergy is the cornerstone for achieving high selectivity and efficiency. To conclude, we will offer perspectives on future developments and outline the key challenges that remain. We hope this review inspires future work in both fundamental research and engineering, advancing the field toward industrial high-selectivity photocatalytic CO2 conversion.
Electrocatalytic polymer electrolyte membrane water electrolysis (PEMWE), including both proton and anion exchange membrane water electrolysis, involves oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode, but still faces significant technical bottlenecks such as sluggish reaction kinetics and poor operational stability. To address these limitations, designing advanced electrocatalysts and understanding their electrocatalytic mechanisms are imperative for accelerating the technological progress of PEMWE. This review provides a comprehensive overview of electrocatalytic reaction mechanisms in both acidic and alkaline media, together with an in-depth analysis of recent advances in non-carbon/carbon-based electrocatalysts and bifunctional electrocatalysts for both the OER and HER. The synthesis strategies, advanced characterization techniques, and performance evaluation metrics of these electrocatalysts are systematically discussed. Key technical challenges are critically analyzed, and future research directions are proposed to guide the innovative design of next-generation electrocatalysts and expedite their practical applications in PEMWE systems.
