Two-dimensional (2D) materials have rapidly emerged as transformative platforms for energy storage and conversion, owing to their atomic-scale thickness, tunable electronic structures, and versatile chemical functionalities. Over the past five years, remarkable advances in material synthesis, interface engineering, and device integration have unlocked new opportunities, yet challenges in stability, scalability, and performance optimization remain. In this roadmap, we provide an updated perspective toward 2030, systematically reviewing eleven representative 2D material classes, which can be broadly grouped into carbon-based materials, inorganic semiconductors, framework materials, and layered nanosheet systems. Their opportunities and challenges in electrochemical energy storage, photocatalysis, and electrocatalysis are highlighted. We believe this roadmap can enrich the development of 2D materials for sustainable energy technologies, and provide useful guidance for both fundamental studies and practical applications in the coming decade.

Replacing the conventional oxygen evolution reaction (OER) by thermodynamically and kinetically superior alternatives, such as the urea oxidation reaction (UOR) or sulfion oxidation reaction (SOR), represents a promising strategy for achieving energy-saving water electrolysis for hydrogen production. In this study, we report a bifunctional electrocatalyst featuring a three-dimensional structure with substantial surface porosity supported on nickel foam, which is composed of Mn-doped Co8FeS8 integrated with Ni3S2 (Mn-Co8FeS8/Ni3S2/ NF). In an electrolyte containing Na2S, it requires only 0.32 V vs. RHE to reach 100 mA cm- 2, significantly lower than the potentials required for OER (1.53 V vs. RHE) and UOR (1.41 V vs. RHE), and exhibits excellent hydrogen evolution reaction (HER) performance. Specifically, the Mn-Co8FeS8/Ni3S2/NF based hybrid water electrolyzer in Na2S solution achieves an ultra-low cell voltage of 1.15 V at 500 mA cm- 2, consuming only 2.82 kWh/m3 H2, as well as stable operation for 200 h at 750 mA cm- 2. UV-vis spectroscopy and in-situ Raman spectroscopy analyses confirm the stepwise oxidation of toxic S2- to polysulfide ions (Sn2-, 2 <= x <= 4), and ultimately to form economically valuable and non-toxic S8 powder. Density functional theory (DFT) calculations indicate that the Mn dopant in Co8FeS8 generates the highly-intrinsic catalytic sites for SOR and HER, as well as a low energy barrier of water dissociation. The in-situ X-ray absorption near-edge structure (XANES) spectroscopy well supports the Fe atoms as catalytic sites during SOR process. Afterwards, the high-value-added sulfur powder also exhibits excellent performance in Li-S batteries due to its uniform particle size compared to the commercial sulfur powder. This study demonstrates that the doping strategy offers a promising pathway for constructing advanced catalysts to achieve energy-saving hydrogen production and treatment of wastewater containing sulfur ions.

ABSTRACT Organometallic macrocyclic molecules have shown great potential to accelerate the reaction kinetics in Li−S batteries. However, it is still challenging to precisely tailor the microenvironment of metal sites and enhance its intrinsic reactivity. Herein, inspired by single‐atom editing in organic chemistry, we prepared a series of isolobal nickel‐based organometallic macrocyclic molecules (denoted as Ni−N x C y ) to optimize the steric configuration and d‐orbital states of Ni sites by tuning the first coordination shell at atom‐level. In situ x‐ray absorption spectroscopy revealed the dynamic evolution of nickel sites, while in situ Raman spectra demonstrated the accelerated sulfur conversion kinetics for Ni−N 2 C 2 in Li−S batteries. Theoretical calculations confirmed that the geometric configuration of Ni−N x C y can be modulated by first‐shell atoms, when the d xy and d x 2 − y 2 orbitals of nickel can be activated for N 2 C 2 ‐coordinated Ni site. In addition, the up‐shift of d‐band center for Ni−N 2 C 2 further facilitates its hybridization with sulfur species. Consequently, cells with Ni−N 2 C 2 deliver 1277 mA h g −1 at 0.5 C, while showing a decay rate of 0.04% at 2 C. Furthermore, an Ah‐level pouch cell with energy density of 393 W h kg −1 can be achieved based on the total mass of cell. This work provides mechanistic insights into the microenvironment regulation of single‐metal‐site and structure–activity relationships in Li−S batteries.

The microenvironment of nitrogen-coordinated single metal (M- Nx) sites significantly impacts the electronic properties and the kinetics of sulfur species in lithium-sulfur (Li-S) batteries. However, accurately designing the M- Nx materials remains challenging, which is crucial for investigating the structure-function relationship and developing high-performance electrocatalysts. Compared with the traditional pyrolyzed M- Nx catalysts, the single-atom metal sites with precise microenvironment can be fabricated with molecularly dispersed MPc loaded on matrix. Herein, we modulate the d-band electronic states by tailoring the molecularly dispersed iron phthalocyanine (FePc) by means of donating/withdrawing (tetraamino, TA/tetranitro, TN) groups with aminofunctionalized carbon nanotube (ACNT) as matrix. The static and dynamic properties between FePc derivatives and LiPSs are investigated by in-situ Raman spectra and quasi-in-situ XPS methods. Density functional theory (DFT) calculations further reveal the enhanced orbital hybridization of 3d pi-2px/y between Fe and S for FeTNPc@ACNT, which improves the reduction of long-chain polysulfides and the dissociation of Li2S. Consequently, cells with FeTNPc@ACNT exhibit a high specific capacity of 1000.9 mA h g- 1 at 2 C, along with a decay rate of 0.041% after 1000 cycles. This study uncovers that peripheral ligand structure regulation selectively steers the redox kinetics in Li-S batteries.

Developing the highly efficient catalysts is a great challenge for accelerating the redox reactions in Li−S batteries. Inspired by the single‐atom catalysts and metalloproteins, it makes full use of the advantages of metal–organic frameworks (MOFs) as electrocatalysts. Herein, a series of 2D metal‐bonded metalloporphyrin MOFs are prepared with 5,10,15,20‐tetrakis(4‐pyridyl) cobalt porphyrin (CoTPyP) as building blocks and transition metals (M═Mn, Fe, Co, Ni, and Cu) as nodes, respectively. The crystalline structures of the bimetallic 2D MOFs are confirmed by UV–vis spectra and X‐ray diffraction analyses. According to DFT calculation, the peripheral metal nodes optimize the electronic state of Co in porphyrin core. Especially, CoTPyP‐Mn facilitates the cleavage of S−S bond from both ends and promotes their conversion kinetics through Co−S and Li−N bonds. The Li−S cells with CoTPyP‐Mn show the initial specific capacity of 1339 mA h g −1 at 0.2 C. The capacity decay rate is only 0.0442% per cycle after 1000 cycles at 2 C. This work achieves the rational control of the central Co d electron state through the peripheral regulation and enriches the application of MOFs in accelerating the redox kinetics in Li−S batteries.

Catalytic conversion of lithium polysulfides (LiPSs) is a crucial approach to enhance the redox kinetics and suppress the shuttle effect in lithium-sulfur (Li-S) batteries. However, the roles of a typical heterogenous catalyst cannot be easily identified due to its structural complexity. Compared with the distinct sites of single atom catalysts (SACs), each active site of single site catalysts (SSCs) is identical and uniform in their spatial energy, binding mode, and coordination sphere, etc. Benefiting from the well-defined structure, iron phthalocyanine (FePc) is covalently clicked onto CuO nanosheet to prepare low spin-state Fe SSCs as the model catalyst for Li-S electrochemistry. The periodic polarizability evolution of Fe-N bonding is probed during sulfur redox reaction by in situ Raman spectra. Theoretical analysis shows the decreased d-band center gap of Fe (Δd) and delocalization of dxz/dyz after the axial click confinement. Consequently, Li-S batteries with Fe SSCs exhibit a capacity decay rate of 0.029% per cycle at 2 C. The universality of this methodological approach is demonstrated by a series of M SSCs (M = Mn, Co, and Ni) with similar variation of electronic configuration. This work provides guidance for the design of efficient electrocatalysis in Li-S batteries.

Spin-engineering with electrocatalysts have been exploited to suppress the “shuttle effect” in Li–S batteries. Spin selection, spin-dependent electron mobility and spin potentials in activation barriers can be optimized as quantum spin exchange interactions leading to a significant reduction of the electronic repulsions in the orbitals of catalysts. Herein, we anchor the MgPc molecules on fluorinated carbon nanotubes (MgPc@FCNT), which exhibits the single active Mg sites with axial displacement. According to the density functional theory calculations, the electronic spin polarization in MgPc@FCNT not only increases the adsorption energy toward LiPSs intermediates but also facilitates the tunneling process of electron in Li–S batteries. As a result, the MgPc@FCNT provides an initial capacity of 6.1 mAh cm−2 even when the high sulfur loading is 4.5 mg cm−2, and still maintains 5.1 mAh cm−2 after 100 cycles. This work provides a new perspective to extend the main group single-atom catalysts enabling high-performance Li–S batteries.

Lithium-sulfur (Li-S) batteries have become an ideal candidate for the next generation of rechargeable batteries for the high theoretical energy density. However, the sluggish redox kinetics hampered the development of Li-S batteries. It is reported that the conversion kinetics of lithium polysulfides (LiPSs) can be accelerated by introducing catalytic materials. The macrocyclic metal porphyrins have attracted extensive attention due to their excellent chemical stability and structural tunability. Herein, we designed a series of iron porphyrins substituted by the electron-donating and electron-withdrawing groups. According to electrochemical characterization and theoretical calculation, the functional group can switch the spin state of central Fe and modulate their catalytic performance. The methoxy-substituted iron porphyrin (FeTPP-4OMe) shows smaller band gap and facilitates the electron transfer. As a result, Li-S batteries with FeTPP-4OMe delivered a specific capacity of 1,062.0 mA h g - 1 and retained a high specific capacity of 771.4 mA h g - 1 at 0.5 C after 500 cycles with a capacity fading of 0.055 %. This work provides a guidance for the functional group modification of metal macrocyclic compounds in Li-S batteries.

Metallic conductive 1T phase molybdenum sulfide (MoS2) has been identified as promising anode for sodium ion (Na+) batteries, but its metastable feature makes it difficult to obtain and its restacking during the charge/discharge processing result in part capacity reversibility. Herein, a synergetic effect of atomic-interface engineering is employed for constructing 2H-MoS2 layers assembled on single atomically dispersed Fe N C (SA Fe N C) anode material that boosts its reversible capacity. The work-function-drivenelectron transfer occurs from SA Fe N C to 2H-MoS2 via the Fe S bonds, which enhances the adsorption of Na+ by 2H-MoS2, and lays the foundation for the sodiation process. A phase transfer from 2H to 1T/2H MoS2 with the ferromagnetic spin-polarization of SA Fe-N-C occurs during the sodiation/desodiation process, which significantly enhances the Na+ storage kinetics, and thus the 1T/2H MoS2/SA Fe N C display a high electronic conductivity and a fast Na+ diffusion rate.

Rechargeable aqueous zinc-ion batteries are promising candidate for grid-scale energy storage. However, the development of zinc-ion batteries has been plagued by the lack of cathode materials with high specific capacity and superior lifespan. Herein, hexagonal Cs0.3V2O5 cathode is fabricated and investigated in zinc-ion batteries. Compared with the traditional vanadium oxides, the introduction of Cs changes the periodic atomic arrangements, which not only stabilizes the open framework structure but also facilitates the Zn2+ diffusion with a lower migration energy barrier. Consequently, high specific capacity of 543.8 mA h g(-1) at 0.1 A g(-1) is achieved, which surpasses most of reported cathode materials in zinc-ion batteries. The excellent cycle life is achieved over 1000 cycles with about 87.8% capacity retention at 2 A g(-1). Furthermore, the morphological evolution and energy storage mechanisms are also revealed via a series of techniques. This work opens up a phase engineering strategy to fabricate the hexagonal vanadium oxide and elucidate the application of phase-dependent cathodes in zinc-ion batteries.

Hydrogen peroxide（H 2 O 2 ） as a multifunctional and environmentally friendly oxidizer,plays a crucial role in industrial production,bleaching,disinfection,and wastewater treatment,etc.The traditional anthraquinone process is not the ideal choice for batch H 2 O 2 production due to the disadvantages of environmental pollution,insecurity,and complicated process.Typically,H 2 O 2 can be synthesized by the 2-electron（2e - ）oxygen reduction reaction（ORR） process,which process is a promising alternative to produce the H 2 O 2 at a large scale.Carbon-based materials are considered as one kind of the best catalysts for 2e - ORR due to their abundant reserves,low cost,adjustable structure,and good conductivity.Therefore,this paper reviews the research progress of carbon-based catalysts in 2e - ORR for H 2 O 2 .Firstly,the basic principle of 2e - ORR is introduced,and the key factors affecting the ORR path are revealed.Then,density functional theory（DFT） employed to reveal the essence of catalytic active sites is introduced.After that,several effective strategies on catalysts for promoting the production of H 2 O 2 are summarized in detail,including optimized single atom catalysts（SACs）,defect engineering on catalyst surface,pyrrole nitrogen doping,oxygen-containing functional groups doping,and other heteroatoms（e.g.S,P,F） doping.At last,the development of the practical applications in the devices for mass production of H 2 O 2 are discussed.Finally,the potential opportunities and challenges in the future development of electrochemical synthesis of H 2 O 2 are proposed.

As a novel type of green energy storage device, supercapacitors exhibit several orders of magnitude higher capacities than the traditional dielectric capacitors and significantly higher power density than the traditional secondary batteries. Supercapacitors have been widely applied in energy storage fields. Electrode materials, as pivotal components of supercapacitors, play an important role in electrochemical performance. Molybdenum-based materials have attracted widespread attention for their high theoretical capacitance, abundant resources, and facile synthesis tactics. Therefore, it is necessary to systematically summarize the application of Mo-based electrode materials in high-performance supercapacitors and unveil their developmental direction and trends. In this paper, we provide a review of binary Mo-based materials, ternary Mo-based materials, nanocomposites of Mo-based materials, and Mo-based MOFs and derivative materials. In addition, we further point out the key issues on the development of Mo-based materials in supercapacitors. This review may inspire more insightful works and enlighten other electrochemical areas concerning Mo-based materials.

In lithium-sulfur (Li-S) batteries, the root-cause solution is to accelerate the polysulfide conversion to their end products by electrocatalysts. Herein, we put forward a molecular spin engineering to break the symmetry of Fe-N-C and achieve the spin modulation for triplet-to-singlet conversion by the ligand field theory. The Fe-N-C shows an 3d-electronic structure of (d xy ) 2 (d xz ) 2 (d yz ) 2 and dramatically speeds up the LPSs conversion kinetics. According to the density functional theory (DFT), there is an upshift of energy levels after the adsorption of LPSs on Fe center. As a result, the optimized catalyst delivers a capacity fading rate of 0.026% per cycle at 2 C. In addition, a high capacity of 1042 mA h g −1 is achieved with satisfied capacity retention with the sulfur loading of about 4 mg cm −2 . This strategy provides a novel route for the regulation of Fe-spin state and the exploration of catalytic effect in Li-S batteries.

With the rapid development of mobile electronic devices and electric vehicles, traditional lithium-ion batteries (LIBs) can no longer satisfy human’s requirement due to the limited energy density. Nowadays, the metal-sulfur/selenium (M-S/Se) batteries have attracted widespread attention due to the high theoretical energy density. Among the M-S/Se batteries, lithium-sulfur (Li-S) batteries receive more attention. Li-S batteries show a high theoretical specific capacity (1675 mA h g–1) and high energy density (2600 W h kg–1). However, Li-S batteries still face some problems: (i) Due to the soluble polysulfide (LiPSs), the “shuttle effect” can cause the loss of sulfur components and corrosion of Li anode. (ii) The electrical conductivity of S8 and Li2S2/Li2S is poor, lots of conductive additives need to be introduced into the sulfur cathode, making the theoretical energy density difficult to be achieved. (iii) The volume change during the charge/discharge processes is about 80%, which leads to the structural collapse. For the M-S/Se batteries, there exist the similar problems to be solved. Over the past years, efforts have been devoted to constructing conductive scaffolds to enhance the specific capacity, cycling stability and rate delivery of M-S/Se batteries. Carbon-based materials present the porous nanostructures and high conductivity, which have been employed as host materials and interlayer materials to promote the electrochemical performance. In this chapter, the investigations of carbon-based materials in M-S/Se batteries are summarized. Finally, carbon-based materials applied in M-S/Se batteries were briefly prospected, aiming at providing some thoughts for the design of electrode materials in M-S/Se batteries.

With the increasing dependence on fossil energy, environmental pollution has become a serious problem for human beings. Renewable energy has been developed to reduce the use of non-renewable sources. Clean energy, such as wind, solar and tidal power, suffers from time and space factors. Therefore, energy storage system is required to match the development of clean energy. Metal-ion batteries (MIBs) have attracted much attention due to their high-energy density and cycle life. Among MIBs, lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and potassium-ion batteries (PIBs) have attracted the most attention. However, metal ion batteries also face some problems. Due to the large radius of sodium/potassium ions, the active site cannot be fully utilized during the insertion/deinsertion process. In addition, charge transfer, ion transfer and volume change should be paid attention to in the exploit of electrode materials. In this regard, carbon-based nanomaterials show great potential. This chapter focuses on the application of carbon-based nanomaterials in MIBs, including metal-free carbon-based materials, atomically dispersed metal on carbon-based materials, metal nanoparticles encapsulated by carbon-based materials and metal nanoparticles supported on carbon-based materials. Finally, the application of carbon-based nanomaterials in metal batteries is briefly prospected, aiming to provide some enlightenment for the design and manufacture of MIBs.

The reversible conversion reaction of a SEI was enabled by FeNX catalysts, which provided novel avenues for designing anode materials. Furthermore, a large number of spin-polarized electrons were stored in the already-reduced Fe species.

Lithium-sulfur(Li-S) batteries have been puzzled by the “shuttle effect”. In the recent years, catalytic materials present a huge potential for solving this problem. However, the exploitation for catalytic activity was still challenging in Li-S batteries. In this article, we put forward a single atom catalyst (SAC) of FeN 4 coupled with Fe 3 C on the N-doped carbon (FeN 4 /Fe 3 C@NC) by one-step pyrolysis method. The FeN 4 and Fe 3 C synergistically catalyze the polysulfides conversion when the N-doped carbon provides the high conductive three-dimensional skeleton in Li-S batteries. As a result, the FeN 4 /Fe 3 C@NC shows a specific capacity of 1100 mA·h/g at 0.2 C(1 C=1675 mA/g). In addition, the FeN 4 /Fe 3 C@NC maintains 99.01% of the pristine specific capacity after 100 cycles at 0.5 C, indicating the improved electrochemical performance in Li-S batteries. This work sheds new lights on the design of engineering catalysts for developing high-performance Li-S batteries.

The aqueous rechargeable batteries (ARBs) are puzzled by the limited cycle life owing to the serious side reactions and instability of the anode materials. Herein, we report the ultrastable triquinoxalinylene (3Q) molecule with multiple redox reactions as anode in aqueous Li + electrolytes over a wide pH range, when the dissolution of anode and hydrolysis of water phenomena are suppressed. The discharged product of 3Q-Li shows relatively higher stability than that of 3Q-Li-H through the density functional theory (DFT) calculations. Furthermore, the 3Q molecule shows the ultrafast Li (+ )storage performance (133.3 mA h g(-1) at 100 A g(-1)) in the strong alkaline Li + electrolyte. The assembled 3Q//Ni(OH)(2) cell shows the ultrastable performance after 200 k cycles. In addition, the universal generality of 3Q anode is demonstrated in the acidic (MnO2 cathode) and neutral (LiMn2O4 cathode) electrolyte medium. This strategy provides a new route for the design of anode materials in ARBs.

SiO is a promising alternative to Si as the anode material for lithium-ion batteries, but it still suffers from a low initial coulomb efficiency, poor electrical conductivity, unstable cycling performance, etc. Various strategies have been attempted to solve these issues but were left unsolved. In this work, we propose a simple strategy that checks all of the right boxes by presetting a lithium source electrolyte (Li2CO3) into a SiO film using the magnetron sputtering method. The preset lithium source electrolyte provides both the lithium ions and the electrolyte required for the formation of a solid electrolyte interphase and thus significantly improves the initial coulomb efficiency. The lithium source electrolyte also acts as a medium to facilitate the growth of a solid electrolyte interphase inside this composite film in addition to its surfaces. The interior interphase provides an efficient and fast pathway for lithium-ion transmission during the lithiation process and thus improves the anode conductivity and the rate performance. The interior interphase also suppresses the brittle fracture by buffering the dramatic volume change during the lithiation/delithiation process and stabilizes the cycling performance substantially. In addition, this strategy is safe, green, and of low-cost, when compared to others, and provides a feasible way to commercialize the SiO anode for lithium-ion batteries.

As low-cost electrocatalysts for oxygen reduction reaction applied to fuel cells and metal-air batteries, atomic-dispersed transition metal-nitrogen-carbon materials are emerging, but the genuine mechanism thereof is still arguable. Herein, by rational design and synthesis of dual-metal atomically dispersed Fe,Mn/N-C catalyst as model object, we unravel that the O 2 reduction preferentially takes place on Fe III in the FeN 4 /C system with intermediate spin state which possesses one e g electron (t 2g 4e g 1) readily penetrating the antibonding π-orbital of oxygen. Both magnetic measurements and theoretical calculation reveal that the adjacent atomically dispersed Mn-N moieties can effectively activate the Fe III sites by both spin-state transition and electronic modulation, rendering the excellent ORR performances of Fe,Mn/N-C in both alkaline and acidic media (halfwave positionals are 0.928 V in 0.1 M KOH, and 0.804 V in 0.1 M HClO 4 ), and good durability, which outperforms and has almost the same activity of commercial Pt/C, respectively. In addition, it presents a superior power density of 160.8 mW cm −2 and long-term durability in reversible zinc–air batteries. The work brings new insight into the oxygen reduction reaction process on the metal-nitrogen-carbon active sites, undoubtedly leading the exploration towards high effective low-cost non-precious catalysts.