Iron, Tungsten Dual-Doped Nickel Sulfide as Efficient Bifunctional Catalyst for Overall Water Splitting.

Developing low-cost and highly efficient bifunctional catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is a challenging problem in electrochemical overall water splitting. Here, iron, tungsten dual-doped nickel sulfide catalyst (Fe/W-Ni3S2) is synthesized on the nickel foam, and it exhibits excellent OER and HER performance. As a result, the water electrolyze based on Fe/W-Ni3S2 bifunctional catalyst illustrates 10 mA cm-2 at 1.69 V (without iR-compensation) and highly durable overall water splitting over 100 h tested under 500 mA cm-2. Experimental results and DFT calculations indicate that the synergistic interaction between Fe doping and Ni vacancy induced by W leaching during the in situ oxidation process can maximize exposed OER active sites on the reconstructed NiOOH species for accelerating OER kinetics, while the Fe/W dual-doping optimizes the electronic structure of Fe/W-Ni3S2 and the binding strength of intermediates for boosting HER. This study unlocks the different promoting mechanisms of incorporating Fe and W for boosting the OER and HER activity of Ni3S2 for water splitting, which provides significant guidance for designing high-performance bifunctional catalysts for overall water splitting.

In-situ confining selenium within bubble - like carbon nanoshells for ultra-stable Li-Se batteries.

Lithium-selenium (Li-Se) batteries are promising energy storage devices. However, the long-term durability and high-rate performance of the Se cathode have been limited by significant volume expansion and the troublesome shuttle effect of polyselenides during repeated charging/discharging processes. To revolutionize these issues, we applied a top-down strategy through the in-situ trapping of amorphous Se within bubble-like carbon (BLC) frameworks, which can radically minimize the presence of surface-absorbed Se while enhancing Se loading capacity. This ingenious technique successfully encapsulates all Se species within carbon nanoshells, creating a distinct half-filled core-shell structure known as Se@void@BLC. This in-situ trapping approach ensures the efficient management of Se volume changes during repeated discharge and charge cycles. Moreover, an extraordinary Se loading capacity of up to 65.6 wt% is reached. Using the Se@void@BLC as cathode for Li-Se battery, we achieve a high initial Columbic efficiency of 84.2 %, a high reversible capacity of 585 mAh g-1, and an ultralow capacity decay of only 0.0037 % per cycle during 4000 cycles at 10 A g-1.

Hollow Carbon and MXene Dual-Reinforced MoS2 with Enlarged Interlayers for High-Rate and High-Capacity Sodium Storage Systems.

Sodium-ion batteries (SIBs) and sodium-ion capacitors (SICs) are promising candidates for cost-effective and large-scale energy storage devices. However, sluggish kinetics and low capacity of traditional anode materials inhibit their practical applications. Herein, a novel design featuring a layer-expanded MoS2 is presented that dual-reinforced by hollow N, P-codoped carbon as the inner supporter and surface groups abundant MXene as the outer supporter, resulting in a cross-linked robust composite (NPC@MoS2 /MXene). The hollow N, P-codoped carbon effectively prevents agglomeration of MoS2 layers and facilitates shorter distances between the electrolyte and electrode. The conductive MXene outer surface envelops the NPC@MoS2 units inside, creating interconnected channels that enable efficient charge transfer and diffusion, ensuring rapid kinetics and enhanced electrode utilization. It exhibits a high reversible capacity of 453 mAh g-1 , remarkable cycling stability, and exceptional rate capability with 54% capacity retention when the current density increases from 100 to 5000 mA g-1 toward SIBs. The kinetic mechanism studies reveal that the NPC@MoS2 /MXene demonstrates a pseudocapacitance dominated hybrid sodiation/desodiation process. Coupled with active carbon (AC), the NPC@MoS2 /MXene//AC SICs achieve both high energy density of 136 Wh kg-1 at 254 W kg-1 and high-power density of 5940 W kg-1 at 27 Wh g-1 , maintaining excellent stability.

Enabling Ultrafine Ru Nanoparticles with Tunable Electronic Structures via a Double-Shell Hollow Interlayer Confinement Strategy toward Enhanced Hydrogen Evolution Reaction Performance.

Engineering of the catalysts' structural stability and electronic structure could enable high-throughput H2 production over electrocatalytic water splitting. Herein, a double-shell interlayer confinement strategy is proposed to modulate the spatial position of Ru nanoparticles in hollow carbon nanoreactors for achieving tunable sizes and electronic structures toward enhanced H2 evolution. Specifically, the Ru can be anchored in either the inner layer (Ru-DSC-I) or the external shell (Ru-DSC-E) of double-shell nanoreactors, and the size of Ru is reduced from 2.2 to 0.9 nm because of the double-shell confinement effect. The electronic structures are efficiently optimized thereby stabilizing active sites and lowering the reaction barrier. According to finite element analysis results, the mesoscale mass diffusion can be promoted in the double-shell configuration. The Ru-DSC-I nanoreactor exhibits a much lower overpotential (η10 = 73.5 mV) and much higher stability (100 mA cm-2). Our work might shed light on the precise design of multishell catalysts with efficient refining electrostructures toward electrosynthesis applications.

Electrolyte and Additive Engineering for Zn Anode Interfacial Regulation in Aqueous Zinc Batteries.

Aqueous Zn-metal batteries (AZMBs) have gained great interest due to their low cost, eco-friendliness, and inherent safety, which serve as a promising complement to the existing metal-based batteries, e.g., lithium-metal batteries and sodium-metal batteries. Although the utilization of aqueous electrolytes and Zn metal anode in AZMBs ensures their improved safety over other metal batteries meanwhile guaranteeing their decent energy density at the cell level, plenty of challenges involved with metallic Zn anode still await to be addressed, including dendrite growth, hydrogen evolution reaction, and zinc corrosion and passivation. In the past years, several attempts have been adopted to address these problems, among which engineering the aqueous electrolytes and additives is regarded as a facile and promising approach. In this review, a comprehensive summary of aqueous electrolytes and electrolyte additives will be given based on the recent literature, aiming at providing a fundamental understanding of the challenges associated with the metallic Zn anode in aqueous electrolytes, meanwhile offering a guideline for the electrolytes and additives engineering strategies toward stable AZMBs in the future.

A quasi-solid polymer electrolyte initiated by two-dimensional functional nanosheets for stable lithium metal batteries.

Lithium-metal batteries (LMBs) are expected to serve as next-generation energy storage systems due to their high theoretical energy density. However, their practical application is largely impeded due to the safety risks that arise from the uncontrollable Li dendrite growth and the high reactivity between high flammability liquid organic electrolytes and metallic lithium. Here, we report a highly safe quasi-solid gel polymer electrolyte (GPE) to achieve stable cycling of lithium metal with high coulombic efficiency, and it is prepared by in situ polymerization of 1,3-dioxolane (DOL) assisted by multi-functional H3Sb3P2O14 sheets. H3Sb3P2O14 acts as an initiator and a functional additive simultaneously that promotes the formation of a stable solid electrolyte interface (SEI) layer, thereby regulating the uniform deposition of Li and improving the Li plating/stripping efficiency. The obtained quasi-solid GPE exhibits high ionic conductivity and enhanced oxidative stability, favoring a stabilized electrode/electrolyte interface. Using the GPE, the electrochemical performance of the quasi-solid-state LMB with a LiFePO4 cathode and a lithium metal anode is significantly improved, delivering a discharge capacity of 125.7 mA h g-1 even after 1000 cycles. Therefore, the high reversibility and remarkable battery cyclability suggest that such a GPE is a promising choice of electrolyte for LMBs, while its facile preparation makes its large-scale application possible in the future.

A 'Moore's law' for fibers enables intelligent fabrics.

Fabrics are an indispensable part of our everyday life. They provide us with protection, offer privacy and form an intimate expression of ourselves through their esthetics. Imparting functionality at the fiber level represents an intriguing path toward innovative fabrics with a hitherto unparalleled functionality and value. The fiber technology based on thermal drawing of a preform, which is identical in its materials and geometry to the final fiber, has emerged as a powerful platform for the production of exquisite fibers with prerequisite composition, geometric complexity and control over feature size. A 'Moore's law' for fibers is emerging, delivering higher forms of function that are important for a broad spectrum of practical applications in healthcare, sports, robotics, space exploration, etc. In this review, we survey progress in thermally drawn fibers and devices, and discuss their relevance to 'smart' fabrics. A new generation of fabrics that can see, hear and speak, sense, communicate, harvest and store energy, as well as store and process data is anticipated. We conclude with a critical analysis of existing challenges and opportunities currently faced by thermally drawn fibers and fabrics that are expected to become sophisticated platforms delivering value-added services for our society.

Edge-hosted Atomic Co-N4 Sites on Hierarchical Porous Carbon for Highly Selective Two-electron Oxygen Reduction Reaction.

Not only high efficiency but also high selectivity of the electrocatalysts is crucial for high-performance, low-cost, and sustainable energy storage applications. Herein, we systematically investigate the edge effect of carbon-supported single-atom catalysts (SACs) on oxygen reduction reaction (ORR) pathways (two-electron (2 e- ) or four-electron (4 e- )) and conclude that the 2 e- -ORR proceeding over the edge-hosted atomic Co-N4 sites is more favorable than the basal-plane-hosted ones. As such, we have successfully synthesized and tuned Co-SACs with different edge-to-bulk ratios. The as-prepared edge-rich Co-N/HPC catalyst exhibits excellent 2 e- -ORR performance with a remarkable selectivity of ≈95 % in a wide potential range. Furthermore, we also find that oxygen functional groups could saturate the graphitic carbon edges under the ORR operation and further promote electrocatalytic performance. These findings on the structure-property relationship in SACs offer a promising direction for large-scale and low-cost electrochemical H2 O2 production via the 2 e- -ORR.

Integrating Covalent Organic Framework with Transition Metal Phosphide for Noble-Metal-Free Visible-Light-Driven Photocatalytic H2 Evolution.

2D covalent organic frameworks (COFs) are considered as one kind of the most promising crystalline porous materials for solar-driven hydrogen production. However, adding noble metal co-catalysts into the COFs-based photocatalytic system is always indispensable. Herein, through a simple solvothermal synthesis method, TpPa-1-COF, a typical 2D COF, which displays a wide light absorption region, is rationally combined with transition metal phosphides (TMPs) to fabricate three TMPs/TpPa-1-COF hybrid materials, named Ni12 P5 (Ni2 P or CoP)/TpPa-1-COF. The incorporated TMPs can be served as electron collectors for accelerating the transfer of charges on TpPa-1-COF, thus the composites are demonstrated to be efficient photocatalysts for promoting water splitting. Benefitting from the richer surface reactive sites and lower H* formation energy barrier, the Ni12 P5 can most effectively improve the photocatalytic performance of the TpPa-1-COF, and the H2 evolution rate can reach up to 31.6 µmol h-1 , approximately 19 times greater than pristine TpPa-1-COF (1.65 µmol h-1 ), and is comparable to the Pt/TpPa-1-COF (38.8 µmol h-1 ). This work is the first example of combining COFs with TMPs to construct efficient photocatalysts, which may offer new insight for constructing noble-metal-free COF-based photocatalysts.

Hetero-Shelled Hollow Structure Coupled with Non-Thermal Plasma Inducing Spatial Charge Rearrangement for Superior NO Conversion and Sulfur Resistance.

Facilitating the mass transfer and spatial charge separation is a great challenge for achieving efficient oxidation of NO and outstanding sulfur resistance. Herein, a hydrothermal-assisted confinement growth technique is used to fabricate well-defined three-dimensional CuOx@MnOx hetero-shelled hollow-structure catalysts. By integrating the coupled plasma space reactor and the porous hierarchical structure of the catalyst, excellent stability (10 h) and high conversion of NO (93.86%) are reached under the concentration of SO2 (1000 mg m-3 ) and NO (200 mg m-3 ). Impressively, precise surface characterization and detailed density functional theory calculations show that the spatial hetero-shelled micro-reactor can orient the redox pairs transportation, facilitating the combination of NO with the surface coordinately unsaturated O atoms, and also prevent the poisoning of SO2 molecules due to the curvature and surface charge effect in the non-thermal plasma equipment.

Interpolation between W Dopant and Co Vacancy in CoOOH for Enhanced Oxygen Evolution Catalysis.

Electronic structure engineering via integrating two defect structures with opposite modulation effects holds the key to fully unlocking the power of a catalyst. Herein, an interpolation principle is proposed to activate CoOOH via W doping and Co vacancies for the oxygen evolution reaction. Density functional theory suggests opposite roles for the W dopant and the Co vacancy but a synergy between them in tuning the electronic states of the Co site, leading to near-ideal intermediate energetics and dramatically lowered catalytic overpotential. Experimental studies confirm the modulation of the electronic structure and validate the greatly enhanced catalytic activity with a small overpotential of 298.5 mV to drive 50 mA cm-2 . The discovery of the interpolation between dopants and vacancies opens up a new methodology to design efficient catalysts for various electrochemical reactions.

Atomically Thin Materials for Next-Generation Rechargeable Batteries.

Atomically thin materials (ATMs) with thicknesses in the atomic scale (typically <5 nm) offer inherent advantages of large specific surface areas, proper crystal lattice distortion, abundant surface dangling bonds, and strong in-plane chemical bonds, making them ideal 2D platforms to construct high-performance electrode materials for rechargeable metal-ion batteries, metal-sulfur batteries, and metal-air batteries. This work reviews the synthesis and electronic property tuning of state-of-the-art ATMs, including graphene and graphene derivatives (GE/GO/rGO), graphitic carbon nitride (g-C3N4), phosphorene, covalent organic frameworks (COFs), layered transition metal dichalcogenides (TMDs), transition metal carbides, carbonitrides, and nitrides (MXenes), transition metal oxides (TMOs), and metal-organic frameworks (MOFs) for constructing next-generation high-energy-density and high-power-density rechargeable batteries to meet the needs of the rapid developments in portable electronics, electric vehicles, and smart electricity grids. We also present our viewpoints on future challenges and opportunities of constructing efficient ATMs for next-generation rechargeable batteries.

Rational design of metal oxide catalysts for electrocatalytic water splitting.

Electrocatalytic energy conversion between electricity and chemical bonding energy is realized through redox reactions with multiple charge transfer steps at the electrode-electrolyte interface. The surface atomic structure of the electrode materials, if appropriately designed, will provide an energetically affordable pathway with individual reaction intermediates that not only reduce the thermodynamic energy barrier but also allow an acceptably fast kinetic rate of the overall redox reaction. As one of the most abundant and stable forms, oxides of transitional metals demonstrated promising electrocatalytic activities towards multiple important chemical reactions. In this topical review, we attempt to discuss the possible avenues to construct the electrocatalytic active surface for this important class of materials for two essential chemical reactions for water splitting. A general introduction of the electrochemical water splitting process on the electrocatalyst surface with applied potential will be provided, followed by a discussion on the fundamental charge transfers and the mechanism. As the generally perceived active sites are chemical reaction dependent, we offer a general overview of the possible approaches to construct or create electrocatalytically active sites in the context of surface atomic structure engineering. The review concludes with perspectives that summarize challenges and opportunities in electrocatalysis and how these can be addressed to unlock the electrocatalytic potentials of the metal oxide materials.

Robust Pseudocapacitive Sodium Cation Intercalation Induced by Cobalt Vacancies at Atomically Thin Co1-x Se2 /Graphene Heterostructure for Sodium-Ion Batteries.

Electronic structure engineering on electrode materials could bring in a new mechanism to achieve high energy and high power densities in sodium ion batteries. Herein, we design and create Co vacancies at the interface of atomically thin CoSe2 /graphene heterostructure and obtain Co1-x Se2 /graphene heterostructure electrode materials that facilitate significant Na+ intercalation pseudocapacitance. Density functional theory (DFT) calculation suggests that the Na+ adsorption energy is dramatically increased, and the Na+ diffusion barrier is remarkably reduced due to the introduction of Co vacancy. The optimized electrode delivers a superior capacity of 673.6 mAh g-1 at 0.1 C, excellent rate capability of 576.5 mAh g-1 at 2.0 C and ultra-long life up to 2000 cycles. Kinetics analysis indicates that the enhanced Na+ storage is mainly attributed to the intercalation pseudocapacitance induced by Co vacancies. This work suggests that the creation of cation vacancy could bestow heterostructured electrode materials with pseudocapacitive Na+ intercalation for high-capacity and high-rate energy storage.

Coexisting Single-Atomic Fe and Ni Sites on Hierarchically Ordered Porous Carbon as a Highly Efficient ORR Electrocatalyst.

The development of oxygen reduction reaction (ORR) electrocatalysts based on earth-abundant nonprecious materials is critically important for sustainable large-scale applications of fuel cells and metal-air batteries. Herein, a hetero-single-atom (h-SA) ORR electrocatalyst is presented, which has atomically dispersed Fe and Ni coanchored to a microsized nitrogen-doped graphitic carbon support with unique trimodal-porous structure configured by highly ordered macropores interconnected through mesopores. Extended X-ray absorption fine structure spectra confirm that Fe- and Ni-SAs are affixed to the carbon support via FeN4 and NiN4 coordination bonds. The resultant Fe/Ni h-SA electrocatalyst exhibits an outstanding ORR activity, outperforming SA electrocatalysts with only Fe- or Ni-SAs, and the benchmark Pt/C. The obtained experimental results indicate that the achieved outstanding ORR performance results from the synergetic enhancement induced by the coexisting FeN4 and NiN4 sites, and the superior mass-transfer capability promoted by the trimodal-porous-structured carbon support.

Phosphorus and Sulfur Co-Doped Cobaltous Oxide Synthesized by an Inorganic-Salt-Assisted Method: Reaction Mechanism and Electrocatalytic Application.

An inorganic-salt-assisted synthesis of non-metallic heteroatom (phosphorus and sulfur) co-doped cobaltous oxide (P/S-CoO) has been reported. Potassium sulphate (K2 SO4 ) was used as inorganic source of sulfur (S), while triphenyl phosphine (PPh3 ) was used as phosphorus (P) source. A stepwise mechanistic investigation into the doping process revealed that the decomposition of PPh3 triggered the release of both the elemental sulfur and phosphorus because of the reducing reaction environment. The transformation of cobalt-PPh3 complex into cubic cobalt (II) oxide along with the successful co-doping (P and S) was achieved by high temperature calcination at 800 °C but preserved the bulk CoO crystalline structure. The as synthesized P/S-CoO demonstrated an unprecedented enhancement on the oxygen evolution activity compare to that of pristine CoO with the current density of 10 mA/cm2 at the overpotential of 293 mV in 1.0 M KOH electrolyte and profound stability at different current densities.

Approaching the activity limit of CoSe2 for oxygen evolution via Fe doping and Co vacancy.

Electronic structure engineering lies at the heart of efficient catalyst design. Most previous studies, however, utilize only one technique to modulate the electronic structure, and therefore optimal electronic states are hard to be achieved. In this work, we incorporate both Fe dopants and Co vacancies into atomically thin CoSe2 nanobelts for /coxygen evolution catalysis, and the resulted CoSe2-DFe-VCo exhibits much higher catalytic activity than other defect-activated CoSe2 and previously reported FeCo compounds. Deep characterizations and theoretical calculations identify the most active center of Co2 site that is adjacent to the VCo-nearest surface Fe site. Fe doping and Co vacancy synergistically tune the electronic states of Co2 to a near-optimal value, resulting in greatly decreased binding energy of OH* (ΔEOH) without changing ΔEO, and consequently lowering the catalytic overpotential. The proper combination of multiple defect structures is promising to unlock the catalytic power of different catalysts for various electrochemical reactions.

Interface Engineering of CoS/CoO@N-Doped Graphene Nanocomposite for High-Performance Rechargeable Zn-Air Batteries.

Low cost and green fabrication of high-performance electrocatalysts with earth-abundant resources for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for the large-scale application of rechargeable Zn-air batteries (ZABs). In this work, our density functional theory calculations on the electrocatalyst suggest that the rational construction of interfacial structure can induce local charge redistribution, improve the electronic conductivity and enhance the catalyst stability. In order to realize such a structure, we spatially immobilize heterogeneous CoS/CoO nanocrystals onto N-doped graphene to synthesize a bifunctional electrocatalyst (CoS/CoO@NGNs). The optimization of the composition, interfacial structure and conductivity of the electrocatalyst is conducted to achieve bifunctional catalytic activity and deliver outstanding efficiency and stability for both ORR and OER. The aqueous ZAB with the as-prepared CoS/CoO@NGNs cathode displays a high maximum power density of 137.8 mW cm-2, a specific capacity of 723.9 mAh g-1 and excellent cycling stability (continuous operating for 100 h) with a high round-trip efficiency. In addition, the assembled quasi-solid-state ZAB also exhibits outstanding mechanical flexibility besides high battery performances, showing great potential for applications in flexible and wearable electronic devices.

2D Electrocatalysts for Converting Earth-Abundant Simple Molecules into Value-Added Commodity Chemicals: Recent Progress and Perspectives.

The electrocatalytic conversion of earth-abundant simple molecules into value-added commodity chemicals can transform current chemical production regimes with enormous socioeconomic and environmental benefits. For these applications, 2D electrocatalysts have emerged as a new class of high-performance electrocatalyst with massive forward-looking potential. Recent advances in 2D electrocatalysts are reviewed for emerging applications that utilize naturally existing H2 O, N2 , O2 , Cl- (seawater) and CH4 (natural gas) as reactants for nitrogen reduction (N2 → NH3 ), two-electron oxygen reduction (O2 → H2 O2 ), chlorine evolution (Cl- → Cl2 ), and methane partial oxidation (CH4 → CH3 OH) reactions to generate NH3 , H2 O2 , Cl2 , and CH3 OH. The unique 2D features and effective approaches that take advantage of such features to create high-performance 2D electrocatalysts are articulated with emphasis. To benefit the readers and expedite future progress, the challenges facing the future development of 2D electrocatalysts for each of the above reactions and the related perspectives are provided.