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Abstract The discovery of Mn-Ca complex in photosystem II stimulates research of manganese-based catalysts for oxygen evolution reaction (OER). However, conventional chemical strategies face challenges in regulating the four electron-proton processes of OER. Herein, we investigate alpha-manganese dioxide (α-MnO2) with typical MnIV-O-MnIII-HxO motifs as a model for adjusting proton coupling. We reveal that pre-equilibrium proton-coupled redox transition provides an adjustable energy profile for OER, paving the way for in-situ enhancing proton coupling through a new “reagent”— external electric field. Based on the α-MnO2 single-nanowire device, gate voltage induces a 4-fold increase in OER current density at 1.7 V versus reversible hydrogen electrode. Moreover, the proof-of-principle external electric field-assisted flow cell for water splitting demonstrates a 34% increase in current density and a 44.7 mW/cm² increase in net output power. These findings indicate an in-depth understanding of the role of proton-incorporated redox transition and develop practical approach for high-efficiency electrocatalysis.

Abstract The integration of flexible micro‐ and nanodevices plays a pivotal role in investigating stress‐enhanced performances and underlying intrinsic mechanisms for two‐dimensional materials. This study presents the fabrication of single‐crystal flexible devices using monolayer MoS2 and its catalytic activities for the hydrogen evolution reaction under stress conditions. A metallic conductive layer was deposited on the photoresist surface via magnetron sputtering, overcoming the challenges associated with lithography on insulating substrates using electron beam lithography (EBL). The results demonstrate optimal etch patterns with a metal modification layer thickness of 10.97 nm. Leveraging this flexible device fabrication process, a single‐layer MoS2 single‐nanosheet flexible micro/nano device was developed and subsequently strain‐modulated (stretched along the zigzag lattice direction with the armchair lattice direction as the axis). A significant enhancement is observed in the electrocatalytic hydrogen evolution performance as the strain increases from 0 % to 0.40 %. Notably, the onset overpotential decreased from 155.6 to 95.7 mV, and the Tafel slope decreased from 175.3 to 98.6 mV dec−1. This study provides new insights into the design and performance of strain devices for two‐dimensional (2D) monocrystalline/polycrystalline materials.

Abstract Due to their extensive microporous structure, metal‐organic frameworks (MOFs) find widespread application in constructing modification layers, functioning as ion sieves. However, the modification layers prepared by existing methods feature gaps between MOFs that are noticeably larger than the inherent MOF pore dimensions. Polysulfides and lithium ions unavoidably permeate through these gaps, hindering the full exploitation of the structural advantages. Herein, an ultrathin (20 nm) and crack‐free MOF film is formed on the separator by atomic layer deposition for the first time. Based on the separator, the mechanism of different MOF layers has been verified by phase field simulation and in situ Raman spectroscopy. The results accurately prove that the MOF particle layer can relieve the shuttle of polysulfides, but it does not have the effect of homogenizing lithium ions. Only the ultrathin and crack‐free MOF film with proper pore size can act as the ion sieve for both polysulfides and lithium ions. As a result, under the test condition of 2 mA cm−2–2 mAh cm−2, the overpotential of the Li/Li symmetric battery is only 18 mV after 2500 h. The capacity retention rate of the lithium–sulfur battery is 95.6% after 500 cycles and 80% after 1000 cycles at 2 C.

Highlights Comprehensive insights into Prussian blue analogs for aqueous sodium- and potassium-ion batteries. Unveiling the dissolution mechanism of transition metal ions in Prussian blue analogs. Innovative solutions to suppression transition metal ion dissolution, spanning electrolyte engineering, transition metal doping/substitution, minimize defects, and composite materials.

Abstract Molten salt aluminum-sulfur batteries are based exclusively on resourcefully sustainable materials, and are promising for large-scale energy storage owed to their high-rate capability and moderate energy density; but the operating temperature is still high, prohibiting their applications. Here we report a rapid-charging aluminium-sulfur battery operated at a sub-water-boiling temperature of 85 °C with a tamed quaternary molten salt electrolyte. The quaternary alkali chloroaluminate melt – possessing abundant electrochemically active high-order Al-Cl clusters and yet exhibiting a low melting point – facilitates fast Al3+ desolvation. A nitrogen-functionalized porous carbon further mediates the sulfur reaction, enabling the battery with rapid-charging capability and excellent cycling stability with 85.4% capacity retention over 1400 cycles at a charging rate of 1 C. Importantly, we demonstrate that the asymmetric sulfur reaction mechanism that involves formation of polysulfide intermediates, as revealed by operando X-ray absorption spectroscopy, accounts for the high reaction kinetics at such temperature wherein the thermal management can be greatly simplified by using water as the heating media.

Bismuth has garnered significant interest as an anode material for magnesium batteries (MBs) because of its high volumetric specific capacity and low working potential. Nonetheless, the limited cycling performance (≤100 cycles) limits the practical application of Bi as anode for MBs. Therefore, the improvement of Bi cycling performance is of great significance to the development of MBs and is also full of challenges. Here, Bi nanoparticles encapsulated in nitrogen-doped carbon with single-atom Bi embedded (Bi@NC) are prepared and reported as an anode material for MBs. Bi@NC demonstrates impressive performance, with a high discharge capacity of 347.5 mAh g−1 and good rate capability (206.4 mAh g−1@500 mA g−1) in a fluoride alkyl magnesium salt electrolyte. In addition, Bi@NC exhibits exceptional long-term stability, enduring 400 cycles at 500 mA g−1. To the best of our knowledge, among reported Bi and Bi-based compounds for MBs, Bi@NC exhibits the longest cycle life in this work. The magnesium storage mechanism of Bi@NC is deeply studied through X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. This work provides some guidance for further improving the cycling performance of other alloy anodes in MBs.

Abstract Electrochemical conversion of CO2 to formic acid using Bismuth catalysts is one the most promising pathways for industrialization. However, it is still difficult to achieve high formic acid production at wide voltage intervals and industrial current densities because the Bi catalysts are often poisoned by oxygenated species. Herein, we report a Bi3S2 nanowire-ascorbic acid hybrid catalyst that simultaneously improves formic acid selectivity, activity, and stability at high applied voltages. Specifically, a more than 95% faraday efficiency was achieved for the formate formation over a wide potential range above 1.0 V and at ampere-level current densities. The observed excellent catalytic performance was attributable to a unique reconstruction mechanism to form more defective sites while the ascorbic acid layer further stabilized the defective sites by trapping the poisoning hydroxyl groups. When used in an all-solid-state reactor system, the newly developed catalyst achieved efficient production of pure formic acid over 120 hours at 50 mA cm–2 (200 mA cell current).

Abstract Vanadium nitride (VN) electrode displays high‐rate, pseudocapacitive responses in aqueous electrolytes, however, it remains largely unclear in nonaqueous, Na+‐based electrolytes. The traditional view supposes a conversion‐type mechanism for Na+ storage in VN anodes but does not explain the phenomena of their size‐dependent specific capacities and underlying causes of pseudocapacitive charge storage behaviors. Herein, we insightfully reveal the VN anode exhibits a surface‐redox pseudocapacitive mechanism in nonaqueous, Na+‐based electrolytes, as demonstrated by kinetics analysis, experimental observations, and first‐principles calculations. Through ex situ X‐ray photoelectron spectroscopy and semiquantitative analyses, the Na+ storage is characterized by redox reactions occurring with the V5+/V4+ to V3+ at the surface of VN particles, which is different from the well‐known conversion reaction mechanism. The pseudocapacitive performance is enhanced through nanoarchitecture design via oxidized vanadium states at the surface. The optimized VN‐10 nm anode delivers a sodium‐ion storage capability of 106 mAh g−1 at the high specific current of 20 A g−1, and excellent cycling performance of 5000 cycles with negligible capacity losses. This work demonstrates the emerging opportunities of utilizing pseudocapacitive charge storage for realizing high‐rate sodium‐ion storage applications.

Rechargeable aqueous zinc metal battery has been one of the next‐generation energy storage systems with a promising future due to the advantages of aqueous electrolyte and metallic zinc anode. Among many cathode materials, vanadium‐based materials with considerable specific capacity, adjustable crystal structure, and multiple valence states are very promising cathodes, but the electrochemical performance of vanadium‐based zinc metal batteries faces severe challenges such as the limited and declining capacity and sluggish ion/e− transport kinetics process. Herein, taking VO2 as an example, the crystal structure and energy storage mechanism of VO2 cathode are briefly introduced. The challenges of aqueous Zn/VO2 battery are analyzed in depth. Significantly, the current advanced modification strategies for aqueous Zn/VO2 battery are summarized and discussed in detail, and the future development is also prospected. This article can provide some significant references for the development of aqueous Zn/VO2 battery and the guiding significance for other metal ion battery.

Controlling the morphology of Pt-based nanostructures can provide a great opportunity to boost their catalytic activity and durability. Here the authors report anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires for oxygen reduction reaction with enhanced mass activity and stability.

Abstract Solid‐state electrolytes are critical for the development of next‐generation high‐energy and high‐safety rechargeable batteries. Among all the candidates, sodium (Na) superionic conductors (NASICONs) are highly promising because of their evident advantages in high ionic conductivity and high chemical/electrochemical stability. The concept of NASICONs was proposed by Hong and Goodenough et al. in 1976 by reporting the synthesis and characterization of Na1+xZr2(SixP3−x)O12 (0 ≤ x ≤ 3), which has attracted tremendous attention on the NASICONs‐type solid‐state electrolytes. In this review, we are committed to describing the development history of NASICONs‐type solid‐state electrolytes and elucidating the contribution of Goodenough as a tribute to him. We summarize the correlations and differences between lithium‐based and sodium‐based NASICONs electrolytes, such as their preparation methods, structures, ionic conductivities, and the mechanisms of ion transportation. Critical challenges of NASICONs‐structured electrolytes are discussed, and several research directions are proposed to tackle the obstacles toward practical applications.

While acidic water splitting offers a renewable means to obtain renewable hydrogen fuel, the catalysts needed to oxidize water often require expensive noble metals. Here, authors show manganese oxyhalides as acidic oxygen evolution electrocatalysts.

Abstract Rechargeable magnesium batteries are identified as a promising next‐generation energy storage system, but their development is hindered by the anode−electrolyte−cathode incompatibilities and passivation of magnesium metal anode. To avoid or alleviate these problems, the exploitation of alternative anode materials is a promising choice. Herein, we present titanium pyrophosphate (TiP2O7) as anode materials for magnesium‐ion batteries (MIBs) and investigate the effect of the crystal phase on its magnesium storage performance. Compared with the metastable layered TiP2O7, the thermodynamically stable cubic TiP2O7 displays a better rate capability of 72 mAh g−1 at 5000 mA g−1. Moreover, cubic TiP2O7 exhibits excellent cycling stability with the capacity of 60 mAh g−1 after 5000 cycles at 1000 mA g−1, which are better than previously reported Ti‐based anode materials for MIBs. In situ X‐ray diffraction technology confirms the single‐phase magnesium‐ion intercalation/deintercalation reaction mechanism of cubic TiP2O7 with a low volume change of 3.2%. In addition, the density functional theory calculation results demonstrate that three‐dimensional magnesium‐ion diffusion can be allowed in cubic TiP2O7 with a low migration energy barrier of 0.62 eV. Our work demonstrates the promise of TiP2O7 as high‐rate and long‐life anode materials for MIBs and may pave the way for further development of MIBs.

Metal-organic frameworks (MOFs) have been regarded as one of the most promising materials for efficient energy conversion technologies, especially heterogeneous catalysis, since they were initially developed. Recently, one-dimensional (1D) MOFs and their derived materials have shown great potential for electrocatalysis owing to the combination of the characteristics of 1D structure and MOFs, such as favorable charge transfer, adjustable metal center, abundant active sites and porous structure. This review focuses first on the synthesis and structure of 1D MOF materials, and briefly summarizes the application in electrocatalysis. Two main methods, i.e., template-assisted and template-free methods, are introduced by typical examples and the obtained different 1D structures are analyzed. Then the application of 1D MOF and its derived materials are comprehensively described and the structural merits of heterogeneous electrocatalysis are emphasized. Although many 1D MOFs have been developed, exploring a simple and high-yield method to prepare high-crystallized 1D MOF materials for electrocatalysis remains a great challenge. We aim to present the state of the 1D MOFs in the field of electrocatalysis and contribute to the rational design and synthesis of 1D MOFs.

Abstract Solid-state electrolyte (SSE) of the sodium-ion battery have attracted tremendous attention in the next generation energy storage materials on account of their wide electrochemical window and thermal stability. However, the high interfacial impedance, low ion transference number and complex preparation process restrict the application of SSE. Herein, inspired by the excellent sieving function and high specific surface area of red blood cells, we obtained a solid-like electrolyte (SLE) based on the combination of the pancake-like metal–organic framework (MOF) with liquid electrolyte, possessing a high ionic conductivity of 6.60 × 10–4 S cm−1, and excellent sodium metal compatibility. In addition, we investigated the ion restriction effect of MOF’s apertures size and special functional groups, and the ion transference number increased from 0.16 to 0.33. Finally, the assembled Na0.44MnO2//SLE//Na full batteries showed no obvious capacity decrease after 160 cycles. This material design of SLE in our work is an important key to obtain fast ion migration SLE for high-performance sodium-ion batteries.

Abstract High-performance and low-cost sodium-ion capacitors (SICs) show tremendous potential applications in public transport and grid energy storage. However, conventional SICs are limited by the low specific capacity, poor rate capability, and low initial coulombic efficiency (ICE) of anode materials. Herein, we report layered iron vanadate (Fe5V15O39 (OH)9·9H2O) ultrathin nanosheets with a thickness of ~ 2.2 nm (FeVO UNSs) as a novel anode for rapid and reversible sodium-ion storage. According to in situ synchrotron X-ray diffractions and electrochemical analysis, the storage mechanism of FeVO UNSs anode is Na+ intercalation pseudocapacitance under a safe potential window. The FeVO UNSs anode delivers high ICE (93.86%), high reversible capacity (292 mAh g−1), excellent cycling stability, and remarkable rate capability. Furthermore, a pseudocapacitor–battery hybrid SIC (PBH-SIC) consisting of pseudocapacitor-type FeVO UNSs anode and battery-type Na3(VO)2(PO4)2F cathode is assembled with the elimination of presodiation treatments. The PBH-SIC involves faradaic reaction on both cathode and anode materials, delivering a high energy density of 126 Wh kg−1 at 91 W kg−1, a high power density of 7.6 kW kg−1 with an energy density of 43 Wh kg−1, and 9000 stable cycles. The tunable vanadate materials with high-performance Na+ intercalation pseudocapacitance provide a direction for developing next-generation high-energy capacitors.

Abstract Amorphous carbon shows great potential as an anode material for high-performance potassium-ion batteries; however, its abundant defects or micropores generally capture K ions, thus resulting in high irreversible capacity with low initial Coulombic efficiency (ICE) and limited practical application. Herein, pore engineering via a facile self-etching strategy is applied to achieve mesoporous carbon (meso-C) nanowires with interconnected framework. Abundant and evenly distributed mesopores could provide short K+ pathways for its rapid diffusion. Compared to microporous carbon with highly disordered structure, the meso-C with Zn-catalyzed short-range ordered structure enables more K+ to reversibly intercalate into the graphitic layers. Consequently, the meso-C shows an increased capacity by ~ 100 mAh g−1 at 0.1 A g−1, and the capacity retention is 70.7% after 1000 cycles at 1 A g−1. Multiple in/ex situ characterizations reveal the reversible structural changes during the charging/discharging process. Particularly, benefiting from the mesoporous structure with reduced specific surface area by 31.5 times and less defects, the meso-C generates less irreversible capacity with high ICE up to 76.7%, one of the best reported values so far. This work provides a new perspective that mesopores engineering can effectively accelerate K+ diffusion and enhance K+ adsorption/intercalation storage.

Abstract Transition metal oxides (TMOs) are considered as the prospective anode materials in lithium‐ion batteries (LIBs). Nevertheless, the disadvantages, including large volume variation and poor electrical conductivity, obstruct these materials to meet the needs of practical application. Well‐designed mesoporous nanostructures and electronic structure modulation can enhance the electron/Li‐ions diffusion kinetics. Herein, a unique mesoporous molybdenum dioxide/molybdenum phosphide heterostructure nanobelts (meso‐MoO2/MoP‐NBs) composed of uniform nanoparticles is obtained by one‐step phosphorization process. The Mott–Schottky tests and density functional theory calculations demonstrated that meso‐MoO2/MoP‐NBs possesses superior electronic conductivity. The detailed lithium storage mechanism (solid solution reaction for MoP and partial conversion for MoO2), small change ratio of crystal structure and fast electronic/ionic diffusion behavior of meso‐MoO2/MoP‐NBs are systematically investigated by operando X‐ray diffraction, ex situ transmission electron microscopy, and kinetic analysis. Benefiting from the synergistic effects, the meso‐MoO2/MoP‐NBs displays a remarkable cycling performance (515 mAh g−1 after 1000 cycles at 1 A g−1) and excellent rate capability (291 mAh g−1 at 8 A g−1). These findings can shed light on the behavior of the electron/ion regulation in heterostructures and provide a potential route to develop high‐performance lithium‐ion storage materials.

As one of the most important micro energy storage devices (MESDs), graphene-based micro-supercapacitors (G-MSCs) possess the advantages of excellent flexibility, long cycle life, affordability and high reliability. In most cases, constructing three-dimensional (3D) graphene networks is widely utilized to promote the permeation of electrolyte and enhance the utilization of active materials. In this work, conventional freeze-drying process is utilized in the fabrication of G-MSCs to constitute 3D interconnected networks micro-electrodes, and further by regulating the composition of inks, carbon spheres (CSs) at different mass loadings are introduced into the graphene scaffolds to further increase the active sites of the micro-electrodes. The fabricated all carbon-based MSC with the optimal mass loading of CSs (0.406 mg cm−2) exhibits a high specific areal capacitance of 17.01 mF cm−2 at the scan rate of 10 mV s−1 and a capacitance retention of 93.14% after 10000 cycles at the scan rate of 500 mV s−1. The proposed microfabrication process is facile and fully compatible with modern microtechnologies and will be highly suitable for large-scale production and integration. Keywords: Three-dimensional, Injecting, Freeze-drying, Mass loading, Supercapacitor

Summary: The understanding and control of the structural complexity of mesoporous semiconductors with single-crystal-like nature are both attractive and challenging. Here, we report a crystallization-driven epitaxial assembly from monomicelles to construct branched mesoporous TiO2 mesocrystals (m-TiO2 MCs) with coherent atomic domains. The star-shaped multipods are obtained by two-step evaporation with nanocrystal mediation, primarily consisting of arms along < 001 >, < 101 >, and < 111 > crystal directions. For each arm, ordered open mesochannels arrange in parallel along the growth direction. The m-TiO2 MC multipods have a surface area of ∼116 m2/g and single-crystal-like frameworks and are good hydrogen evolution photocatalysts. Under full-spectrum irradiation, the branched m-TiO2 MCs exhibit a hydrogen evolution rate of 8 mmol h−1 g−1, which is more than four times higher than that of commercial TiO2 P25. This crystallization-driven self-assembly approach may provide valuable insight into designing programmable mesoporous mesocrystals by controlling the oriented assembly of monomicelle building blocks.

Abstract High energy density lithium metal batteries (LMBs) are promising next‐generation energy storage devices. However, the uncontrollable dendrite growth and huge volume change limit their practical applications. Here, a new Mg doped Li–LiB alloy with in situ formed lithiophilic 3D LiB skeleton (hereinafter called Li–B–Mg composite) is presented to suppress Li dendrite and mitigate volume change. The LiB skeleton exhibits superior lithiophilic and conductive characteristics, which contributes to the reduction of the local current density and homogenization of incoming Li+ flux. With the introduction of Mg, the composite achieves an ultralong lithium deposition/dissolution lifespan (500 h, at 0.5 mA cm−2) without short circuit in the symmetrical battery. In addition, the electrochemical performance is superior in full batteries assembled with LiCoO2 cathode and the manufactured composite. The currently proposed 3D Li–B–Mg composite anode may significantly propel the advancement of LMB technology from laboratory research to industrial commercialization.

Lithium metal batteries suffer from the dendrite growth upon electrochemical cycling. Here the authors introduce a lithiophilic-lithiophobic gradient interfacial ZnO/CNT layer, which facilitates the formation of a stable solid electrolyte interphase, and suppresses the growth of lithium dendrite.

Summary: Sodium ion capacitors (SICs) are designed to deliver both high energy and power densities at low cost. Electric double-layer capacitive cathodes are typically used in these devices, but they lead to very limited capacity. Herein, we apply a pseudocapacitive layered ferric vanadate (Fe-V-O) as cathode to construct non-aqueous SICs with both high energy and power densities. The Fe-V-O nanosheets cathode displays remarkable rate capability and cycling stability. The pseudocapacitive sodium storage mechanism of Fe-V-O, with over 83% of total capacity from capacitive contribution, is confirmed by kinetics analysis and ex situ characterizations. The capacitive-adsorption mechanism of hard carbon (HC) anode is demonstrated, and it delivers excellent rate capability. Based on as-synthesized materials, the assembled HC//Fe-V-O SIC delivers a maximum energy density of 194 Wh kg−1 and power density of 3,942 W kg−1. Our work highlights the advantages of pseudocapacitive cathodes for achieving both high energy and power densities in sodium storage devices. : Electrochemical Energy Storage; Energy Materials; Nanoelectrochemistry Subject Areas: Electrochemical Energy Storage, Energy Materials, Nanoelectrochemistry

Electrocatalysis offers important opportunities for clean fuel production, but uncovering the chemistry at the electrode surface remains a challenge. Here, the authors exploit a single-nanosheet electrode to perform in-situ measurements of water oxidation electrocatalysis and reveal a crucial interaction with oxygen.

The development of suitable anode materials is essential to advance sodium-ion battery technologies. Here the authors report that alkaline earth metal vanadates are promising candidates due to the favorable electrochemical properties and interesting sodium-storage mechanism.

Carbons dominate anode materials for supercapacitors, however the attained energy density remains low. Here the authors fabricate low-crystalline iron oxide-hydroxide nanoparticle anodes with good electrochemical characteristics, exhibiting high stability and energy/power densities in a hybrid supercapacitor.

Lithiation modification of MoO3 nanobelts was carried out by a simple hydrothermal method. The structure and morphology of the directly lithiated MoO3 nanobelts were characterized by XRD and SEM. The results show that, compared to that of pristine MoO3 nanobelts, the size of lithiated MoO3 nanobelts with a width of about 200 nm and a length of 5~8 μm decreases, while preserving crystal structure and belt-shape morphology. The lithiated MoO3 nanobelts exhibit good cycling capability, with a capacity retention rate of 50% after 39 cycles, while the non-lithiated nanobelts retain only 26.5%. It is proposed that the Li+ ions occupy the interstitial site of MoO3 lattice which can stabilize the structure and reduce the electrostatic interaction between MoO3 layer and Li+ ions in the interlayer during the discharge, resulting in the improvement of electrochemical performance.

PEO doped MoO3 nanobelts were synthesized by using a versatile hydrothermal method. The structure and morphology of the products were characterized by XRD, IR and SEM. The results indicate that PEO doped MoO3 nanobelts with length of 1~8 μm and thickness of 50 nm can be fabricated without using any template. Compared to the pure MoO3 nanobelts, PEO doped MoO3 nanobelts exhibit lower discharge capacity, however, the intercalation of PEO into MoO3 nanobelts significantly enhances the cycling stability and reversibility of insertion/extraction of Li+ ions in the materials.