Construction of a built-in electric field has been identified as an attractive improvement strategy for photoelectrochemical (PEC) water splitting by facilitating the carrier extraction from the inside to the surface. However, the promotion effect of the electric field is still restrained by the confined built-in area. Herein, we construct a microscale built-in electric field via gradient oxygen doping. The octahedral configuration of the synthesized CdIn2S4 (CIS) provides a structural basis, which enables the subsequent oxygen doping to reach a depth of similar to 100 nm. Accordingly, the oxygen-doped CIS (OCIS) photoanode exhibits a microscale built-in electric field with band bending. Excellent PEC catalytic activity with a photocurrent density of 3.69 mA cm(-2) at 1.23 V vs. RHE is achieved by OCIS, which is 3.1 times higher than that of CIS. Combining the results of thorough characterization and theoretical calculations, accelerating migration and separation of charge carriers have been determined as the reasons for the improvement. Meanwhile, the recombination risk at the doping centers has also been reduced to the minimum via optimal experiments. This work provides a new-generation idea for constructing a built-in electric field from the view point of bulky configuration towards PEC water splitting.

Oxygen vacancy engineering is a promising strategy to enhance the electrocatalytic activities in conventional metal oxide electrocatalysts. However, the utilization of oxygen vacancies in high-entropy oxides remains unknown, primarily due to the challenges associated with facile introduction of the oxygen vacancies and explanation of their roles in complex high-entropy systems. Herein, the facile introduction of oxygen vacancies into high-entropy oxides is realized and the unique high entropy-driven role of oxygen vacancies for oxygen evolution reaction (OER) process is revealed. A low-temperature surface carbonization-decarbonization approach is developed to introduce and regulate the oxygen vacancies in high-entropy spinel oxides (HEOs). The oxygen vacancies in HEOs can both facilitate pre-oxidation process for faster OH- adsorption and induce the unique bridge site pathway for easier deprotonation, distinctive in conventional oxides where oxygen vacancies favor *OH adsorption yet hinder the deprotonation. Consequently, the as-prepared high-entropy spinel oxides with oxygen vacancies (HEOs-Ov) exhibit superior OER activities, outperforming the HEOs and most reported oxide-based electrocatalysts. Besides, this universal method can be extended to other spinel oxides with different configuration entropies and can be scaled up. The work paves the way for the exploration of oxygen vacancies in high-entropy oxides toward electrocatalysis fields.

Geometrical configurations play a crucial role in dual-atom catalysts (DACs) for electrocatalytic applications. Significant progress has been made to design DACs electrocatalysts with various geometrical configurations, but in-depth understanding the relationship between geometrical configurations and metal-metal interaction mechanisms for designing targeted DACs is still required. In this review, the recent progress in engineering of geometrical configurations of DACs is systematically summarized. Based on the polarity of geometrical configuration, DACs can be classified into two different types that are homonuclear and heteronuclear DACs. Furthermore, with regard to the geometrical configurations of the active sites, homonuclear DACs are identified into adjacent and bridged configurations, and heteronuclear DACs can be classified into adjacent, bridged, and separated configurations. Subsequently, metal-metal interactions in DACs with different geometrical configurations are introduced. Additionally, the applications of DACs in different electrocatalytic reactions are discussed, including the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and other catalysis. Finally, the future challenges and perspectives for advancements in DACs are highlighted. This review aims to provide inspiration for the design of highly efficient DACs towards energy related applications.

Water evaporation-induced electricity generation is a promising technology for renewable energy harvesting. However, the output power of some reported two-dimensional (2D) nanofluidic films is still restricted by the relatively weak water–solid interactions within the tortuous nanochannels. To further enhance the comprehension and utilization of water–solid interactions, it is of utmost importance to conduct an in-depth investigation and propose a regulatory concept encompassing ion transport. Herein, we propose tortuosity regulation of 2D nanofluidic titanium oxide (Ti0.87O2) films to optimize the ion transport within the interlayer nanochannel for enhanced efficiency in water evaporation-induced electricity generation for the first time. The significance of tortuosity in ion transport is elucidated by designing three 2D nanofluidic films with different tortuosity. Tortuosity analysis and in situ Raman measurement demonstrate that low tortuosity can facilitate the formation of efficient pathways for hydrated proton transport and promote water–solid interactions. Consequently, devices fabricated with the optimized 2D nanofluidic films exhibited a significantly enhanced output power density of approximately 204.01 µW·cm−2, far exceeding those prepared by the high-tortuosity 2D nanofluidic films. This work highlights the significance of the construction of low tortuosity channels for 2D nanofluidic films with excellent performance.

Flexible lithium metal batteries with high capacity and power density have been regarded as the core power resources of wearable electronics. However, the main challenge lies in the limited electrochemical performance of solid-state polymer electrolytes, which hinders further practical applications. Incorporating functional inorganic additives is an effective approach to improve the performance, including increasing ionic conductivity, achieving dendrite inhibiting capability, and improving safety and stability. Herein, this review summarizes the latest developments of functional inorganic additives in composite solid-state electrolytes for flexible metal batteries with special emphasis on their mechanisms, strategies, and cutting-edge applications, in particular, the relationship between them is discussed in detail. Finally, the perspective on future research directions and the key challenges on this topic are outlooked.

Electrochemical water splitting, hailed for its cost-effectiveness and eco-friendliness in hydrogen energy production, faces a significant impediment in the form of the oxygen evolution reaction (OER), charac-terized by inherently slow kinetics. Addressing this challenge, the utilization of crystalline-amorphous (c-a) heterostructures, offering precise interface modulation, emerges as a promising solution. In this study, we report the synthesis of a robust electrode comprising of crystalline Ni4.5Fe4.5S8 nanospheres integrated with amorphous NiFeS nanosheets (denoted as NiFeS-TH) using a hydrothermal approach. Remarkably, this electrode exhibits exceptional performance in alkaline electrolytes, requiring a mere overpotential of 420 mV to attain a current density of 2 A/cm2. This enhanced OER performance is attributed to the substantial electrochemically active surface area and the presence of compressive strain at the interfaces. These profound insights into heterostructure design hold the potential to revolutionize the tailoring and optimization of OER efficiency.(c) 2023 Published by Elsevier Ltd.

Supramolecular chemistry during the synthesis of carbon-nitrogen-based materials has recently experienced a renaissance in the arena of photocatalysis and electrocatalysis. In this review, we start with the discussion of supramolecular assemblies-derived carbon-nitrogen-based materials’ regulation from the aspect of morphology, chemical composition, and micro/nanostructural control. Afterwards the recent advances of these materials in energy and environment related applications, including degradation of pollutants, water splitting, oxygen reduction reactions, CO2 reduction reactions along with organic synthesis are summarized. The correlations between the structural features and physicochemical properties of the carbon-nitrogen-based materials and the specific catalytic activity are discussed in depth. By highlighting the opportunities and challenges of supramolecular assembly strategies, we attempt an outlook on possible future developments for highly efficient carbon-based photo/electrocatalysts.

Extending the potential range of MnO2 is imperative to improve power density and capacity density for supercapacitors. However, MnO2 usually suffers from severe Mn dissolution, irreversible phase transition, and poor cycling performance under an extended potential range. Herein, a ligand field regulation strategy is rationally designed to enhance the structural stability of delta-MnO2 to extend the potential window to 0-1.3 V (vs. Ag/AgCl). As revealed, the generated strong covalent B-O plane triangle or P-O tetrahedron configuration effectively decreases the lattice O activity of delta-MnO2. The B-O-Mn and P-O-Mn bonding interactions enhance Mn ion crystal field stabilization energy in the MnO6 octahedra. Therefore, the lattice O loss, Mn dissolution, and irreversible phase transition are well suppressed. The PO43- doped delta-MnO2 electrodes (with a high mass loading of similar to 10 mg cm(-2)) can deliver a large specific capacitance (268.3 F g(-1) at 0.5 A g(-1)) and excellent cycling performance (83.5% after 10000 cycles) in the extended potential window of 0-1.3 V (vs. Ag/AgCl). Our ligand field regulation strategy affords opportunities for developing simultaneously high-capacity and high-voltage electrodes for supercapacitors.

Osmotic power, a clean energy source, can be harvested from the salinity difference between seawater and river water. However, the output power densities are hampered by the trade-off between ion selectivity and ion permeability. Here we propose an effective strategy of double angstrom-scale confinement (DAC) to design ion-permselective channels with enhanced ion selectivity and permeability simultaneously. The fabricated DAC-Ti 0.87 O 2 membranes possess both Ti atomic vacancies and an interlayer free spacing of ≈2.2 Å, which not only generates a profitable confinement effect for Na + ions to enable high ion selectivity but also induces a strong interaction with Na + ions to benefit high ion permeability. Consequently, when applied to osmotic power generation, the DAC-Ti 0.87 O 2 membranes achieved an ultrahigh power density of 17.8 W m −2 by mixing 0.5/0.01 M NaCl solution and up to 114.2 W m −2 with a 500-fold salinity gradient, far exceeding all the reported macroscopic-scale membranes. This work highlights the potential of the construction of DAC ion-permselective channels for two-dimensional materials in high-performance nanofluidic energy systems.

Carbon materials with the merits of superior conductivity and wide available resources have emerged as promising anode candidates for sodium-ion batteries (SIBs). However, the inferior capacitance and the limited interlayer spacing restrain their practical application. Herein, we report an atom-adjustable doping strategy to fabricate the N/P dual-doped porous carbon nanosheet anodes (NP-PCN) via the in situ pyrolysis of supermolecules. Nitrogen atoms and phosphorus atoms are introduced to the skeleton with the monomers assembled incrementally. Benefiting from its monomer processability, the supermolecules demonstrate a rationally designed topological structure, endowing the derived carbon anode with a homogeneous heteroatom dispersion with 25.00 at. % of nitrogen and 6.37 at. % of phosphor, an expanded interlayer spacing of 0.47 nm, as well as an optimized configuration of more pyridinic N. Accordingly, the resulting NP-PCN achieves an enhanced reversible capacity of 223 mAh g(-1) at 100 mA g(-1), a robust rate capability of 114 mAh g(-1) at 1000 mA g(-1), and a long cycle life of 4000 cycles with a capacity retention of 92.60%. The storage mechanism is also explored by in situ Raman spectra and galvanostatic intermittent titration technique. This work may inspire new possibility of designing high-performance carbon anodes toward rechargeable alkali-metal-ion batteries at an atomic level.

Driven by the increasing demand for portable electronics, grid-scale storage, and electric vehicles, 22 the intensive research of electrochemical energy storage (EES) devices with high performance, cost-23 efficient and environmental friendliness has always been at the forefront of energy science and 24 technology. Rechargeable metal-ion energy storage devices are considered to be the promising 25 candidates for sustainable large smart grids and renewable electrochemical energy storage 26 technologies owing to their high specific energy density, affordable cost, and long charge/discharge 27 cycle life. The electrochemical properties and performance of these devices are intimately dependent 28 on the physicochemical nature of their electrode materials, the critical component of an energy Overall, we thank all the authors for their meaningful work and would also like to thank all the 99 reviewers for their insightful suggestions and constructive comments. It is hoped that this special 100 issue will stimulate future research on the discovery and design of novel electrodes and drive the 101 intensive ongoing development of high-energy-density rechargeable energy storage devices. We 102 anticipate that these endeavors will pave a way for achieving green growth and stainable 103 development. 104FZ: writing and review. YD, JZ, PX, PW and HL: co-drafting and editing. All authors have made a 106 substantial, direct and intellectual contribution and approved the submitted version.

Perovskite-type ABO(3) transition metal oxides are promising electrocatalysts for oxygen evolution reaction (OER), but still suffer from insufficient activities. Traditional efforts are mainly based on a single-site doping of heteroatom ions into either B-sites or O-sites of the ABO(3) structures. Here we propose a dual-site doping strategy by simultaneous incorporation of iodine cations and anions into the B-sites and O-sites of ABO(3) perovskite oxides, respectively. Consequently, both activated B-site transition metals with optimal e(g) orbital occupancy and large amount of active oxygen species were achieved for remarkably improved OER activities. Using this approach, significantly improved OER activities are achieved in some representative perovskite oxides, including Ba0.5Sr0.5(Co0.8Fe0.2)(0.9)O3-delta (BSCF), SrCo0.9O3-delta (SCO) and SrNi0.9O3-delta (SNO). Specifically, the iodine dual-site doped BSCF boosts a small overpotential of 290 mV at 10 mA cm(-2) and a small Tafel slope of 53 mV dec(-1), which is about 130 mV and almost half times lower than that of pristine BSCF, respectively. Besides, this general dual-site doping strategy can also realize scale-up synthesis and achieve a gram-scale production. Our findings show a unique doping strategy to design efficient perovskite oxide electrocatalysts beyond the conventional approaches.

Dual single-atom catalysts (DSACs) with maximized atomic utilization efficiency largely depend on stabilization of dual-metallic single atoms on ideal supports, such as those two-dimensional (2D) atomic layers with open double-sided surfaces. However, the modulation of metal-2D support interactions is critical for enhancing the catalytic performance of DSACs, which has rarely been achieved by routine 2D atomic nanosheets. Here we report a soft template-directed interlayer confinement route for the synthesis of a Fe-Co DSAC. Fe and Co single atoms are stabilized separately on 2D carbon nanosheets via coordination with nitrogen (N) and sulfur (S) heteroatoms to form a FeN4S1/CoN4S1 configuration. The synergistic effect of Fe-Co dual metal centers can optimize the adsorption/desorption features and decrease the reaction barriers for enhanced oxygen reduction reaction (ORR) activities. The Fe-Co DSAC exhibits outstanding electrocatalytic activities of ORR with a half-wave potential of 0.86 V and Zn-air batteries with a maximum power density of 152.8 mW cm(-2), outperforming the monometallic Fe and Co SACs. This work paves a new avenue for synthesis of effective DSACs for high-performance electro-catalysis.

The vigorous development of photocatalytic water splitting technology has laid the foundation for the photo catalytic transfer hydrogenation of organic substrates to produce the high value-added chemicals using water as hydrogen source. Nevertheless, the high dissociation energy of the O-H bond impedes its academic progress and the practical applications. Herein, we synthesize a 3D hierarchical porous loofah-like carbon nitride sponge (LCN) with ultrathin thickness via the supramolecular pre-organization coupling with the oxidation etching process, in which the heterogeneous oxygen atoms and the nitrogen vacancies are in-situ engineered. On top of the adorable photocatalytic H2 evolution (4812 mu mol h(-1) g(-1)), LCN associated with Pt cocatalyst reveals a conversion rate of 96.5 % towards the hydrogenation of 4-nitrophenol, substantially superior to the reference experiment (8.3 %). Further based on the isotope-labeling tests and the density functional theory calculations, the photo-generated H0 from water is clarified to be the direct reducing agent, tactfully skipping the hydrogen extraction step in the traditional path. This work provides a green and sustainable methodology to transfer the solar energy to the valuable fine chemicals, as well as highlights the importance of the 3D hierarchical porous structure to the catalytic activity.

Perovskite-type transition metal oxides have emerged as promising electrocatalysts for various electrocatalytic reactions owing to their low cost, compositional tunability and high stability. However, insufficient electrocatalytic activities of pristine perovskite oxides hinder their pathway towards real-world applications. The incorporation of heteroatoms into perovskite oxide structures has been regarded as an efficient way to improve the electrocatalytic performance. This minireview summarizes the recent advances in the heteroatom doping of perovskite oxides as efficient electrocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). These heteroatom doping strategies are classified based on various types of doping sites. The mechanisms of improved electrocatalytic activities are discussed in detail within different doping sites and various kinds of dopants. Finally, the remaining challenges and perspectives are outlined for future developments of perovskite oxide-based catalysts.

Abstract Graphitic carbon nitride (g-C3N4)-based photocatalysts have shown great potential in the splitting of water. However, the intrinsic drawbacks of g-C3N4, such as low surface area, poor diffusion, and charge separation efficiency, remain as the bottleneck to achieve highly efficient hydrogen evolution. Here, a hollow oxygen-incorporated g-C3N4 nanosheet (OCN) with an improved surface area of 148.5 m2 g−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere, wherein the C–O bonds are formed through two ways of physical adsorption and doping. The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects, leading to the formation of hollow morphology, while the O-doping results in reduced band gap of g-C3N4. The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6 μmol g−1 h−1 for ~ 20 h, which is over four times higher than that of g-C3N4 (850.1 μmol g−1 h−1) and outperforms most of the reported g-C3N4 catalysts.

Potassium‐ion batteries based on conversion/alloying reactions have high potential applications in new‐generation large‐scale energy storage. However, their applications are hindered by inherent large‐volume variations and sluggish kinetics of the conversion/alloying‐type electrode materials during the repeated insertion and extraction of bulky K + ions. Although some efforts have been focused on this issue, the reported potassium‐ion batteries still suffer from poor cycling lifespans. Here, a superior stable antimony selenide (Sb 2 Se 3 ) anode is reported for high‐performance potassium‐ion batteries through a combined strategy of conductive encapsulation and 2D confinement. The Sb 2 Se 3 nanorods are uniformly coated with a conductive N‐doped carbon layer and then confined between graphene nanosheets. The synergistic effects between conductive coating and confinement effectively buffer the large volumetric variation of the conversion/alloying anodes, which can maintain structural stability for superior cyclability. The as‐prepared anodes exhibit a high reversible specific capacity of ≈590 mA h g −1 and outstanding cycling stability over 350 cycles. In situ and ex situ characterizations reveal a high structural integration of the large‐volume‐change Sb 2 Se 3 anodes during a reversible K storage mechanism of two‐step conversion and multistep alloying processes. This work can open up a new possibility for the design of stable conversion/alloying‐based anodes for high‐performance potassium‐ion batteries.

ConspectusFlexible and wearable electronics have recently sparked intense interest in both academia and industry because they can greatly revolutionize human lives by impacting every aspect of our daily routine. Therefore, developing compatible energy storage devices has become one of the most important research frontiers in this field. Particularly, the development of flexible electrodes is of great significance when considering their essential role in the performance of these devices. Although there is no doubt that transition metal oxide nanomaterials are suitable for providing electrochemical energy storage, individual oxides generally cannot be developed into freestanding electrodes because of their intrinsically low mechanical strength.Two-dimensional sheets with genuine unilamellar thickness are perfect units for the assembly of freestanding and mechanically flexible devices, as they have the advantages of low thickness and good flexibility. Therefore, the development of metal oxide materials into a two-dimensional sheet morphology analogous to graphene is expected to solve the above-mentioned problems. In this Account, we summarize the recent progress on two-dimensional molecular sheets of transition metal oxides for wearable energy storage applications. We start with our understanding of the principle of producing two-dimensional metal oxides from their bulk-layered counterparts. The unique layered structure of the precursors inspired the exploration of their interlayer chemistry, which helps us to understand the processes of swelling and delamination. Rational methods for tuning the chemical composition, size/thickness, and surface chemistry of the obtained nanosheets and how physicochemical properties of the nanosheets can be modulated are then briefly introduced. Subsequently, the orientational alignment of the anisotropic sheets and the origins of their liquid-crystalline characteristics are discussed, which are of vital importance for their subsequent macroscopic assembly. Finally, macroscopic electrodes with geometric diversity ranging from one-dimensional macroscopic fibers to two-dimensional films/papers and three-dimensional monolithic foams are summarized. The intrinsically low mechanical stiffness of metal oxide sheets can be effectively overcome by wisely designing the assembly mode and sheet interfaces to obtain decent mechanical properties integrated with superior electrochemical performance, thereby providing critical advantages for the fabrication of wearable energy storage devices.We expect that this Account will stimulate further efforts toward fundamental research on interface engineering in metal oxide sheet assembly and facilitate wide applications of their designed assemblies in future new-concept energy conversion devices and beyond. In the foreseeable future, we believe that there will be a big explosion in the application of transition metal oxide sheets in flexible electronics.

Selenium (Se), due to its high electronic conductivity and high energy density, has recently attracted considerable interest as a cathode material for rechargeable Li/Na batteries. However, the poor cycling stability originating from the severe shuttle effect of polyselenides hinders their practical applications. Herein, highly stable Li/Na-Se batteries are developed using ultrathin (approximate to 270 nm, loading of 0.09 mg cm(-2)) cetrimonium bromide (CTAB)/carbon nanotube (CNT)/Ti3C2Tx MXene hybrid modified polypropylene (PP) (CCNT/MXene/PP) separators. The hybrid separator can immobilize the polyselenides via enhanced Lewis acid-base interactions between CTAB/MXene and polyselenides, which is demonstrated by theoretical calculations and X-ray photoelectron spectroscopy. The incorporation of CNT helps to improve the electrolyte infiltration and facilitate the ionic transport. In situ permeation experiments are conducted for the first time to visually study the behavior of polyselenides, revealing the prohibited shuttle effect and protected Li anode from corrosion with CCNT/MXene/PP separators. As a result, the Li-Se batteries with CCNT/MXene/PP separators deliver an outstanding cycling performance over 500 cycles at 1C with an extremely low capacity decay of 0.05% per cycle. Moreover, the hybrid separators also perform well in Na-Se batteries. This study develops a preferable separator-electrolyte interface and the concept can be applied in other conversion-type battery systems.

Water scarcity is one of the most critical issues of this century. Currently, water desalination is performed using polymeric membranes. However, the polymers suffer from low water permeability and degradation, both of which increase energy consumption and the cost of water desalination. There have been several breakthroughs by deploying two-dimensional (2D) materials with the merits of excellent water permeability and chemical resistance, rendering them highly promising as alternative materials of choice for water desalination. However, controlling and maintaining the pores and channels of 2D-based membranes down to the subnanometer level is a challenging process. Herein, we summarized the research progress on 2D materials for membrane-based water desalination. Several nanoporous and stacked membranes of 2D materials are discussed. Design strategies to maintain the stability of the membranes are particularly elucidated, including pore size optimization and interlayer spacing engineering down to subnanometer scales. The current challenges and future research directions are also presented.