Recent Advancements of Graphene-Based Materials for Zinc-Based Batteries: Beyond Lithium-Ion Batteries.

Graphene-based materials (GBMs) possess a unique set of properties including tunable interlayer channels, high specific surface area, and good electrical conductivity characteristics, making it a promising material of choice for making electrode in rechargeable batteries. Lithium-ion batteries (LIBs) currently dominate the commercial rechargeable battery market, but their further development has been hampered by limited lithium resources, high lithium costs, and organic electrolyte safety concerns. From the performance, safety, and cost aspects, zinc-based rechargeable batteries have become a promising alternative of rechargeable batteries. This review highlights recent advancements and development of a variety of graphene derivative-based materials and its composites, with a focus on their potential applications in rechargeable batteries such as LIBs, zinc-air batteries (ZABs), zinc-ion batteries (ZIBs), and zinc-iodine batteries (Zn-I2 Bs). Finally, there is an outlook on the challenges and future directions of this great potential research field.

Two-Dimensional Iron Phosphorus Trisulfide as a High-Capacity Cathode for Lithium Primary Battery.

Metal phosphorus trichalcogenide (MPX3) materials have aroused substantial curiosity in the evolution of electrochemical storage devices due to their environment-friendliness and advantageous X-P synergic effects. The interesting intercalation properties generated due to the presence of wide van der Waals gaps along with high theoretical specific capacity pose MPX3 as a potential host electrode in lithium batteries. Herein, we synthesized two-dimensional iron thio-phosphate (FePS3) nanoflakes via a salt-template synthesis method, using low-temperature time synthesis conditions in single step. The electrochemical application of FePS3 has been explored through the construction of a high-capacity lithium primary battery (LPB) coin cell with FePS3 nanoflakes as the cathode. The galvanostatic discharge studies on the assembled LPB exhibit a high specific capacity of ~1791 mAh g-1 and high energy density of ~2500 Wh Kg-1 along with a power density of ~5226 W Kg-1, some of the highest reported values, indicating FePS3's potential in low-cost primary batteries. A mechanistic insight into the observed three-staged discharge mechanism of the FePS3-based primary cell resulting in the high capacity is provided, and the findings are supported via post-mortem analyses at the electrode scale, using both electrochemical- as well as photoelectron spectroscopy-based studies.

Elemental Two-Dimensional Materials for Li/Na-Ion Battery Anode Applications.

Two-dimensional (2D) nanostructure is currently the subject in the fields of new energy storage and devices. During the past years, a broad range of 2D materials represented by graphene have been developed and endow with excellent electrochemical properties. Among them, elemental 2D materials (Xenes) are an emerged material family for Li/Na-ion battery (LIB/SIB) anodes. Compared with other 2D materials and bulk materials, Xenes may exhibit some great superiorities for Li/Na storage, including excellent conductivity, fast ion diffusion and large active sites exposure. In this review, we provide a systematic summary of the recent progress and achievements of Xenes as well as their applications in LIBs/SIBs. The broad categorization of Xenes from group IIIA to VIA has been concisely outlined, and the related details in syntheses, structures and Li/Na-ion storage properties are reviewed. Further, the latest research progress of Xenes in Li/Na ion batteries are summarized, together with mechanism discussions. Finally, the challenges and prospects of Xenes applied to Li/Na ion battery are proposed based on its current developments.

Constructing Multifunctional Heterostructure of Fe2 O3 @Ni3 Se4 Nanotubes.

Heterostructures have attracted increasing attention due to their amazing synergetic effects, which may improve the electrochemical properties, such as good electrical/ionic conductivity, electrochemical activity, and mechanical stability. Herein, novel hierarchical Fe2 O3 @Ni3 Se4 nanotubes are successfully fabricated by a multistep strategy. The nanotubes show length sizes of ≈250-500 nm, diameter sizes of ≈100-150 nm, and wall thicknesses of ≈10 nm. The as-prepared Fe2 O3 @Ni3 Se4 nanotubes with INi:Fe = 1:10 show excellent Li storage properties (897 mAh g-1 high reversible charge capacity at 0.1 A g-1 ), good rate performance (440 mAh g-1 at 5 A g-1 ), and outstanding long-term cycling performance (440 mAh g-1 at 5 A g-1 during the 300th cycle) as an anode material for lithium ion batteries. In addition, the Fe2 O3 @Ni3 Se4 nanotubes with INi:Fe = 1:10 (the atomic ratio between Ni and Fe) show superior electrocatalytic performance toward the oxygen evolution reaction with an overpotential of only 246 mV at 10 mA cm-2 and a low Tafel slope of 51 mV dec-1 in 1 m KOH solution.

Ultrathin Porous NiFeV Ternary Layer Hydroxide Nanosheets as a Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting.

Herein, the hydrothermal synthesis of porous ultrathin ternary NiFeV layer double hydroxides (LDHs) nanosheets grown on Nickel foam (NF) substrate as a highly efficient electrode toward overall water splitting in alkaline media is reported. The lateral size of the nanosheets is about a few hundreds of nanometers with the thickness of ≈10 nm. Among all molar ratios investigated, the Ni0.75 Fe0.125 V0.125 -LDHs/NF electrode depicts the optimized performance. It displays an excellent catalytic activity with a modest overpotential of 231 mV for the oxygen evolution reaction (OER) and 125 mV for the hydrogen evolution reaction (HER) in 1.0 m KOH electrolyte. Its exceptional activity is further shown in its small Tafel slope of 39.4 and 62.0 mV dec-1 for OER and HER, respectively. More importantly, remarkable durability and stability are also observed. When used for overall water splitting, the Ni0.75 Fe0.125 V0.125 -LDHs/NF electrodes require a voltage of only 1.591 V to reach 10 mA cm-2 in alkaline solution. These outstanding performances are mainly attributed to the synergistic effect of the ternary metal system that boosts the intrinsic catalytic activity and active surface area. This work explores a promising way to achieve the optimal inexpensive Ni-based hydroxide electrocatalyst for overall water splitting.

S-Doped TiSe2 Nanoplates/Fe3 O4 Nanoparticles Heterostructure.

2D Sulfur-doped TiSe2 /Fe3 O4 (named as S-TiSe2 /Fe3 O4 ) heterostructures are synthesized successfully based on a facile oil phase process. The Fe3 O4 nanoparticles, with an average size of 8 nm, grow uniformly on the surface of S-doped TiSe2 (named as S-TiSe2 ) nanoplates (300 nm in diameter and 15 nm in thickness). These heterostructures combine the advantages of both S-TiSe2 with good electrical conductivity and Fe3 O4 with high theoretical Li storage capacity. As demonstrated potential applications for energy storage, the S-TiSe2 /Fe3 O4 heterostructures possess high reversible capacities (707.4 mAh g-1 at 0.1 A g-1 during the 100th cycle), excellent cycling stability (432.3 mAh g-1 after 200 cycles at 5 A g-1 ), and good rate capability (e.g., 301.7 mAh g-1 at 20 A g-1 ) in lithium-ion batteries. As for sodium-ion batteries, the S-TiSe2 /Fe3 O4 heterostructures also maintain reversible capacities of 402.3 mAh g-1 at 0.1 A g-1 after 100 cycles, and a high rate capacity of 203.3 mAh g-1 at 4 A g-1 .

Co9 S8 /MoS2 Yolk-Shell Spheres for Advanced Li/Na Storage.

Uniform sized Co9 S8 /MoS2 yolk-shell spheres with an average diameter of about 500 nm have been synthesized by a facile route. When evaluated as anodes for lithium-ion and sodium-ion batteries, these Co9 S8 /MoS2 yolk-shell spheres show high specific capacities, excellent rate capabilities, and good cycling stability.

Fe-Doped Ni3 C Nanodots in N-Doped Carbon Nanosheets for Efficient Hydrogen-Evolution and Oxygen-Evolution Electrocatalysis.

Uniform Ni3 C nanodots dispersed in ultrathin N-doped carbon nanosheets were successfully prepared by carburization of the two dimensional (2D) nickel cyanide coordination polymer precursors. The Ni3 C based nanosheets have lateral length of about 200 nm and thickness of 10 nm. When doped with Fe, the Ni3 C based nanosheets exhibited outstanding electrocatalytic properties for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For example, 2 at % Fe (atomic percent) doped Ni3 C nanosheets depict a low overpotential (292 mV) and a small Tafel slope (41.3 mV dec-1 ) for HER in KOH solution. An outstanding OER catalytic property is also achieved with a low overpotential of 275 mV and a small Tafel slope of 62 mV dec-1 in KOH solution. Such nanodot-incorporated 2D hybrid structures can serve as an efficient bifunctional electrocatalyst for overall water splitting.

Monolayer Co3 O4 Inverse Opals as Multifunctional Sensors for Volatile Organic Compounds.

Monolayers of periodic porous Co3 O4 inverse opal (IO) thin films for gas-sensor applications were prepared by transferring cobalt-solution-dipped polystyrene (PS) monolayers onto sensor substrates and subsequent removal of the PS template by heat treatment. Monolayer Co3 O4 IO thin films having periodic pores (d≈500 nm) showed a high response of 112.9 to 5 ppm C2 H5 OH at 200 °C with low cross-responses to other interfering gases. Moreover, the selective detection of xylene and methyl benzenes (xylene+toluene) could be achieved simply by tuning the sensor temperature to 250 and 275 °C, respectively, so that multiple gases can be detected with a single chemiresistor. Unprecedentedly high ethanol response and temperature-modulated control of selectivity with respect to ethanol, xylene, and methyl benzenes were attributed to the highly chemiresistive IO nanoarchitecture and to the tuned catalytic promotion of different gas-sensing reactions, respectively. These well-ordered porous nanostructures could have potential in the field of high-performance gas sensors based on p-type oxide semiconductors.

CuO-ZnO micro/nanoporous array-film-based chemosensors: new sensing properties to H2S.

CuO-ZnO micro/nanoporous array-films are synthesized by transferring a solution-dipped self-organized colloidal template onto a device substrate and sequent heat treatment. Their morphologies and structures are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectrum analysis. Based on the sensing measurement, it is found that the CuO-ZnO films prepared with the composition of [Cu(2+)]/[Zn(2+)]=0.005, 0.01, and 0.05 all show a nice sensitivity to 10 ppm H2S. Interestingly, three different zones exist in the patterns of gas responses versus H2S concentrations: a platform zone, a rapidly increasing zone, and a slowly increasing zone. Further experiments show that the hybrid CuO-ZnO porous film sensor exhibits shorter recovery time and better selectivity to H2S gas against other interfering gases at a concentration of 10 ppm. These new sensing properties may be due to a depletion layer induced by p-n junction between p-type CuO and n-type ZnO and high chemical activity of CuO to H2S. This work will provide a new construction route of ZnO-based sensing materials, which can be used as H2S sensors with high performances.

Research progress on layered metal oxide electrocatalysts for an efficient oxygen evolution reaction.

Hydrogen, highly valued for its pristine cleanliness and remarkable efficiency as an emerging energy source, is anticipated to ascend to a preeminent status within the forthcoming energy landscape. Electrocatalytic water splitting is considered a pivotal, eco-friendly, and sustainable strategy for hydrogen production. The substantial energy consumption stemming from oxygen evolution side reactions significantly impedes the commercial viability of water electrolysis. Consequently, the pursuit of a cost-effective and efficacious oxygen evolution reaction (OER) catalyst stands as an imperative strategy for realizing hydrogen production via water electrolysis. Layered metal oxides, owing to their robust anisotropic properties, versatile adjustability, and extensive surface area, have emerged as suitable candidates for OER catalysts. However, owing to the distinctive attributes of layered metal oxides, ongoing investigations into these materials are slightly fragmented, lacking universal consensus. This article comprehensively surveys the recent advancements in layered metal oxide-based OER catalysts, categorized into single metal oxides, alkali cobalt oxides, perovskites, and miscellaneous metal oxides. Initially, the main OER intermediate reaction steps of layered metal oxides are scrutinized. Subsequently, the design, mechanism, and application of several pivotal layered metal oxides in the OER are systematically delineated. Finally, a summary is provided, alongside the proposal of future research trajectories and challenges encountered by layered metal oxides, with the aspiration that this paper may serve as a valuable reference for scholars in the field.

Janus electronic state of supported iridium nanoclusters for sustainable alkaline water electrolysis.

Metal-support electronic interactions play crucial roles in triggering the hydrogen spillover (HSo) to boost hydrogen evolution reaction (HER). It requires the supported metal of electron-rich state to facilitate the proton adsorption/spillover. However, this electron-rich metal state contradicts the traditional metal→support electron transfer protocol and is not compatible with the electron-donating oxygen evolution reaction (OER), especially in proton-poor alkaline conditions. Here we profile an Ir/NiPS3 support structure to study the Ir electronic states and performances in HSo/OER-integrated alkaline water electrolysis. The supported Ir is evidenced with Janus electron-rich and electron-poor states at the tip and interface regions to respectively facilitate the HSo and OER processes. Resultantly, the water electrolysis (WE) is efficiently implemented with 1.51 V at 10 mA cm-2 for 1000 h in 1 M KOH and 1.44 V in urea-KOH electrolyte. This research clarifies the Janus electronic state as fundamental in rationalizing efficient metal-support WE catalysts.

Covalently Bonded Ni Sites in Black Phosphorene with Electron Redistribution for Efficient Metal-Lightweighted Water Electrolysis.

The metal-lightweighted electrocatalysts for water splitting are highly desired for sustainable and economic hydrogen energy deployments, but challengeable. In this work, a low-content Ni-functionalized approach triggers the high capability of black phosphorene (BP) with hydrogen and oxygen evolution reaction (HER/OER) bifunctionality. Through a facile in situ electro-exfoliation route, the ionized Ni sites are covalently functionalized in BP nanosheets with electron redistribution and controllable metal contents. It is found that the as-fabricated Ni-BP electrocatalysts can drive the water splitting with much enhanced HER and OER activities. In 1.0 M KOH electrolyte, the optimized 1.5 wt% Ni-functionalized BP nanosheets have readily achieved low overpotentials of 136 mV for HER and 230 mV for OER at 10 mA cm-2. Moreover, the covalently bonding between Ni and P has also strengthened the catalytic stability of the Ni-functionalized BP electrocatalyst, stably delivering the overall water splitting for 50 h at 20 mA cm-2. Theoretical calculations have revealed that Ni-P covalent binding can regulate the electronic structure and optimize the reaction energy barrier to improve the catalytic activity effectively. This work confirms that Ni-functionalized BP is a suitable candidate for electrocatalytic overall water splitting, and provides effective strategies for constructing metal-lightweighted economic electrocatalysts.

Crack-free periodic porous thin films assisted by plasma irradiation at low temperature and their enhanced gas-sensing performance.

Homogenous thin films are preferable for high-performance gas sensors because of their remarkable reproducibility and long-term stability. In this work, a low-temperature fabrication route is presented to prepare crack-free and homogenous metal oxide periodic porous thin films by oxygen plasma irradiation instead of high temperature annealing by using a sacrificial colloidal template. Rutile SnO2 is taken as an example to demonstrate the validity of this route. The crack-free and homogenous porous thin films are successfully synthesized on the substrates in situ with electrodes. The SnO2 porous thin film obtained by plasma irradiation is rich in surface OH groups and hence superhydrophilic. It exhibits a more homogenous structure and lower resistance than porous films generated by annealing. More importantly, such thin films display higher sensitivity, a lower detection threshold (100 ppb to acetone) and better durability than those that have been directly annealed, resulting in enhanced gas-sensing performance. The presented method could be applied to synthesize other metal oxide homogenous thin films and to fabricate gas-sensing devices with high performances.

An invisible template method toward gold regular arrays of nanoflowers by electrodeposition.

A new approach, an invisible template method that is realized through controlling the interface electroconductivity of an electrode surface, is presented to synthesize gold regular arrays of nanoflowers with variable separations through further electrochemical deposition. Using polystyrene monolayer colloidal crystals as the first template, a hexagonally packed 1-hexadecanethiol pattern was self-assembled and used as an invisible template to control the interface electroconductivity. Further electrochemical deposition under appropriate conditions can easily lead to gold regular arrays of nanoflowers. This new approach demonstrates a simple route to the fabrication of novel gold micro/nanostructured arrays that may find applications as SERS active substrates, superhydrophobic materials, and so forth.

Fabrication of porous Ag hollow sphere arrays based on coated template-plasma bombardment.

A facile and flexible strategy is presented to produce porous Ag hollow sphere arrays, with a micro/nanostructure and contaminant-free surface, based on a combination of the bottom-up and top-down fabrication strategies, or by plasma bombardment of Ag-coated monolayer polystyrene sphere templates. The arrays consist of periodically arranged micro-sized hollow spheres with nanoscaled pores (mostly within 100 nm) in the shell layer. These arrays are structurally tunable in spherical size (in the sub-10 µm range), spacing (from a few nanometers to several microns), shell thickness (over tens of nanometers) and porous configuration by the template and bombarding conditions. The strategy is universal for the fabrication of other porous metal hollow sphere arrays. Such nanoscaled rough and porous Ag hollow sphere arrays have potential applications in catalysis, antibacterial and photonic devices. The arrays show significant surface-enhanced Raman scattering (SERS) activity (the minimum detectable concentration of the standard molecule rhodamine 6G can be down to 10(-14) M) with good stability and reproduction, and are a good candidate for the substrate of SERS effect based devices.

Gel Electrolytes for Electrochemical Actuators and Sensors Applications.

Advanced functional materials, especially gel electrolytes, play a very important role in the preparation of electrochemical actuators and sensors, and have received extensive attention. In this review, a general classification of gel electrolytes is firstly introduced according to the type of medium. Then, the research progress of gel electrolytes with different types used to fabricate electrochemical actuators is summarized. Next, the current research progress of gel electrolytes used in different types of electrochemical sensors, including strain sensors, stress sensors, and gas sensors is introduced. Finally, the future challenges and development prospects of electrochemical actuators and sensors based on gel electrolytes are discussed. The huge application prospects of gel electrolyte are worthy of further focusing by researchers, which will have an indispensable impact on human life and development.

Enlarging the Ni-O Bond Polarizability in a Phosphorene-Hosted Metal-Organic Framework for Boosted Water Oxidation Electrocatalysis.

The emerging lattice-oxygen oxidation mechanism (LOM) presents attractive opportunities for breaking the scaling relationship to boost oxygen evolution reaction (OER) with the direct OLattice-*O interaction. However, currently the LOM-triggering rationales are still debated, and a streamlined physicochemical paradigm is extremely desirable for the design of LOM-defined OER catalysts. Herein, a Ni metal-organic framework/black phosphorene (NiMOF/BP) heterostructure is theoretically profiled and constructed as a catalytic platform for the LOM-derived OER studies. It is found that the p-type BP host can enlarge the Ni-O bond polarizability of NiMOF through the Ni-O bond stretching and Ni valence declining synergically. Such an enlarged bond polarizability will in principle alleviate the lattice oxygen confinement to benefit the LOM pathway and OER performance. As a result, the optimized NiMOF/BP catalyst exhibits promising OER performance with a low overpotential of 260 mV at 10 mA cm-2 and long-term stability in 1 M KOH electrolyte. Both experiment and calculation results suggest the activated LOM pathway with a more balanced step barrier in the NiMOF/BP OER catalyst. This research puts forward Ni-O bond polarizability as the criterion to design LOM-scaled electrocatalysts for water oxidation.

Macroporous SnO2/MoS2 inverse opal hierarchitecture for highly efficient trace NO2 gas sensing.

The innovation of NO2 gas sensors is highly desirable in environmental monitoring and human safety. Herein, a macroporous SnO2/MoS2 inverse opal hierarchitecture has been constructed with substantial interface charge transfer, which realizes the efficient and stable detection of NO2 with an enhanced response, fast kinetics, and high selectivity at low temperatures.

Shining Light on Anion-Mixed Nanocatalysts for Efficient Water Electrolysis: Fundamentals, Progress, and Perspectives.

HIGHLIGHTS: This review introduces recent advances of various anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, (oxy)hydroxides, and borides) for efficient water electrolysis applications in detail. The challenges and future perspectives are proposed and analyzed for the anion-mixed water dissociation catalysts, including polyanion-mixed and metal-free catalyst, progressive synthesis strategies, advanced in situ characterizations, and atomic level structure-activity relationship. Hydrogen with high energy density and zero carbon emission is widely acknowledged as the most promising candidate toward world's carbon neutrality and future sustainable eco-society. Water-splitting is a constructive technology for unpolluted and high-purity H2 production, and a series of non-precious electrocatalysts have been developed over the past decade. To further improve the catalytic activities, metal doping is always adopted to modulate the 3d-electronic configuration and electron-donating/accepting (e-DA) properties, while for anion doping, the electronegativity variations among different non-metal elements would also bring some potential in the modulations of e-DA and metal valence for tuning the performances. In this review, we summarize the recent developments of the many different anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, oxyhydroxides, and borides/borates) for efficient water electrolysis applications. First, we have introduced the general information of water-splitting and the description of anion-mixed electrocatalysts and highlighted their complementary functions of mixed anions. Furthermore, some latest advances of anion-mixed compounds are also categorized for hydrogen and oxygen evolution electrocatalysis. The rationales behind their enhanced electrochemical performances are discussed. Last but not least, the challenges and future perspectives are briefly proposed for the anion-mixed water dissociation catalysts.