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Developing binder-free Cu3N electrode materials by magnetron sputtering for high performance quasi-solid-state asymmetric supercapacitor.

Electrochemical nitrate reduction reaction (NtrRR) towards ammonia, as an emerging and appealing technology alternative to the energy-intensive Haber-Bosch process and inefficient nitrogen reduction reaction, has recently aroused wide concern and research. However, the current research of the NtrRR towards ammonia lacks the overall performance comparison of various electrocatalysts. Given this, we here make a comparison of 12 common transition metal oxide catalysts for the NtrRR under a high cathodic current density of 0.25 A cm-2, wherein Co3O4 catalyst displays the best NtrRR selectivity towards ammonia with a highest Faradaic efficiency (85.15%) and a moderate NtrRR activity. Other external factors, such as nitrate concentrations in the electrolyte and applied potential ranges, have also been specifically investigated for the NtrRR. This work can provide constructive guidance to engineer the NtrRR electrocatalysts with higher activity, selectivity and stability in the future.

Electron-deficient Ru sites at Ru/Co(OH)2 heterointerfaces weaken the d–p orbital hybridization ability and further facilitate the desorption of ammonia intermediates, thereby achieving ultrahigh nitrate electroreduction activity towards ammonia.

This work develops an acid-alkaline furfural hybrid battery that can simultaneously achieve electricity output and bipolar hydrogen production, as well as furoate synthesis by effectively utilizing electrochemical neutralization energy.

Transition metal phosphides (TMPs) are promising candidates for sodium ion battery anode materials because of their high theoretical capacity and earth abundance. Similar to many other P-based conversion type electrodes, TMPs suffer from large volumetric expansion upon cycling and thus quick performance fading. Moreover, TMPs are easily oxidized in air, resulting in a surface phosphate layer that not only decreases the electric conductivity but also hinders the Na ion transport. In this work, we present a general electrode design that overcomes these two major challenges facing TMPs. Using metal hydroxide and glucose as precursors, we show that the metal hydroxide can be converted into phosphide whereas the glucose simultaneously decomposes and forms carbon shell on the phosphide particles under a plasma ambient. Ni2P@C core shell structures as a proof-of-concept are designed and synthesized. The in situ formed carbon shell protects the Ni2P from oxidation. Moreover, the high-energy plasma introduces porosity and vacancies to the Ni2P and more importantly produces phosphorus-rich nickel phosphides (NiPx). As a result, the Ni2P@C electrodes achieve high sodium capacity (693 mAh·g−1 after 50 cycles at 100 mA·g−1) and excellent cyclability (steady capacity maintained for at least 1, 500 cycles). Our work provides a general strategy for enhancing the sodium storage performance of TMPs, and in general many other conversion type electrode materials that are unstable in air and suffer from large volumetric changes upon cycling.

Potassium-ion batteries (PIBs) are appealing alternatives to conventional lithium-ion batteries (LIBs) because of their wide potential window, fast ionic conductivity in the electrolyte, and reduced cost. However, PIBs suffer from sluggish K+ reaction kinetics in electrode materials, large volume expansion of electroactive materials, and the unstable solid electrolyte interphase. Various strategies, especially in terms of electrode design, have been proposed to address these issues. In this review, the recent progress on advanced anode materials of PIBs is systematically discussed, ranging from the design principles, and nanoscale fabrication and engineering to the structure-performance relationship. Finally, the remaining limitations, potential solutions, and possible research directions for the development of PIBs towards practical applications are presented. This review will provide new insights into the lab development and real-world applications of PIBs.

In contrast to alkaline water electrolysis, acidic water electrolysis remains an elusive goal due to the lack of earth-abundant, efficient, and acid-stable water oxidation electrocatalysts. Here, w...

Rechargeable zinc-ion batteries (ZIBs) have shown great potential as an alternative to lithium-ion batteries. The ZIBs utilize Zn metal as the anode, which possesses many advantages such as low cost, high safety, eco-friendliness, and high capacity. However, on the other hand, the Zn anode also suffers from many issues, including dendritic growth, corrosion, and passivation. These issues are largely related to the surface and interface properties of the Zn anode. Many efforts have therefore been devoted to the modification of the Zn anode, aiming to eliminate the above-mentioned problems. This review gives a comprehensive summary on the mechanism behind these issues as well as the recent progress on Zn anode modification with focus on the strategies of surface and interface engineering, covering the design and application of both the Zn anode supports and surface protective layers, along with abundant examples. In addition, the promising research directions and perspective on these strategies are also presented.

The uncontrolled zinc dendrite growth during plating leads to quick battery failure, which hinders the widespread applications of aqueous zinc-ion batteries. The growth of Zn dendrites is often promoted by the "tip effect". In this work, we propose a generate strategy to eliminate the "tip effect" by utilizing the electrostatic shielding effect, which is achieved by coating Zn anodes with magnetron sputtered Al-based alloy protective layers. The Al can form a surface insulating Al

The rapid development of miniaturized and wearable electronics has stimulated growing needs for compatible miniaturized energy storage components. Owing to their unlimited lifetime and high-power density, miniaturized electrochemical capacitors (microsupercapacitors) are considered to be an attractive solution for the development of these microelectronics, but they often depend on the choice of electrode materials and fabrication protocols for scalable production. Recently, a new family of two-dimensional transition metal carbides, carbonitride and nitrides (referred to as MXenes) has shown great promise in advanced microsupercapacitors with high energy and power densities. This was achieved thanks to the high pseudocapacitance, metallic conductivity and ease of solution processing of MXene. In this review, recent progress on MXene synthesis, microstructure design, and fabrication strategies of MXene microsupercapacitors are discussed, and their electrochemical performance is summarized. Further, we briefly discuss the technical challenges and future directions.

International audience; In this work, a pre-designed Zr-based-MOF encompassing an organic linker with a redox active core is synthesized and its structureproperty relationship as a supercapacitor electrode is investigated. An enhanced performance is revealed by the combination of this MOF's high porosity and redox core incorporation, which alters its double-layer and pseudocapacitance, respectively. An increase in the capacitance performance by a factor of two is achieved via post-synthetic structure rigidification using organic pillars.

Hydrogels have recently garnered tremendous interest due to their potential application in soft electronics, human-machine interfaces, sensors, actuators, and flexible energy storage. Benefiting from their impressive combination of hydrophilicity, metallic conductivity, high aspect ratio morphology, and widely tuneable properties, when two-dimensional (2D) transition metal carbides/nitrides (MXenes) are incorporated into hydrogel systems, they offer exciting and versatile platforms for the design of MXene-based soft materials with tunable application-specific properties. The intriguing and, in some cases, unique properties of MXene hydrogels are governed by complex gel structures and gelation mechanisms, which require in-depth investigation and engineering at the nanoscale. On the other hand, the formulation of MXenes into hydrogels can significantly increase the stability of MXenes, which is often the limiting factor for many MXene-based applications. Moreover, through simple treatments, derivatives of MXene hydrogels, such as aerogels, can be obtained, further expanding their versatility. This tutorial review intends to show the enormous potential of MXene hydrogels in expanding the application range of both hydrogels and MXenes, as well as increasing the performance of MXene-based devices. We elucidate the existing structures of various MXene-containing hydrogel systems along with their gelation mechanisms and the interconnecting driving forces. We then discuss their distinctive properties stemming from the integration of MXenes into hydrogels, which have revealed an enhanced performance, compared to either MXenes or hydrogels alone, in many applications (energy storage/harvesting, biomedicine, catalysis, electromagnetic interference shielding, and sensing).

Zinc ion batteries (ZIBs) have been gradually developed in recent years due to their abundant resources, low cost, and environmental friendliness. Therefore, ZIBs have received a great deal of attention from researchers, which are considered as the next generation of portable energy storage systems. However, poor overall performance of ZIBs restricts their development, which is attributed to zinc dendrites and a series of side reactions. Constructing 3D zinc anodes has proven to be an effective way to significantly improve their electrochemical performance. In this review, the challenges of zinc anodes in ZIBs, including zinc dendrites, hydrogen evolution and corrosion, as well as passivation, are comprehensively summarized and the energy storage mechanisms of the zinc anodes and 3D zinc anodes are discussed. 3D zinc anodes with different structures including fiberous, porous, ridge-like structures, plated zinc anodes on different substrates and other 3D zinc anodes, are subsequently discussed in detail. Finally, emerging opportunities and perspectives on the material design of 3D zinc anodes are highlighted and challenges that need to be solved in future practical applications are discussed, hopefully illuminating the way forward for the development of ZIBs.

High power K+ ion capacitors have great potential in various large-scale applications because of the cost advantages and the low redox potential of K/K+. However, the large ionic radius of potassium brings huge challenges for the development of suitable electrode materials. Here we demonstrate a general strategy for preparing porous MXene electrodes that can significantly enhance K+ storage performance. Using V2C MXene as a model system, we show that the K+ ion storage capacity can be greatly boosted by a simple sequential acid/alkali treatment. The resulting product, K–V2C, not only delivers a capacity of 195 mAh g−1 (in contrast to 98 mAh g−1 of pristine V2C) at 50 mA g−1, but also good rate performance. The charge storage mechanism was carefully studied and is shown to involve a solvent co-intercalation process. In addition, full cells were fabricated by coupling the K–V2C anode and Prussian blue analogous (KxMnFe(CN)6) cathode, which can work at a high average operating voltage of ~3.3 V within a wide range (0.01 V–4.6 V). Moreover, the devices can achieve a high energy density of 145 Wh kg−1 at a power density of 112.6 W kg−1, suggesting that K–V2C, and other porous MXenes prepared by our approach, are promising electrodes in mobile ion capacitors.

Inspired by supermolecular self-assembly strategy, the N, P co-doped reduced graphene oxide (NP-rGO) material is fabricated by heat treatment from the supermolecular system of GO/MP (melamine and p...

Aqueous Zn-ion batteries present low-cost, safe, and high-energy battery technology but suffer from the lack of suitable cathode materials because of the sluggish intercalation kinetics associated with the large size of hydrated zinc ions. Herein we report an effective and general strategy to transform inactive intercalation hosts into efficient Zn2+ storage materials through intercalation energy tuning. Using MoS2 as a model system, we show both experimentally and theoretically that even hosts with an originally poor Zn2+ diffusivity can allow fast Zn2+ diffusion. Through simple interlayer spacing and hydrophilicity engineering that can be experimentally achieved by oxygen incorporation, the Zn2+ diffusivity is boosted by 3 orders of magnitude, effectively enabling the otherwise barely active MoS2 to achieve a high capacity of 232 mAh g–1, which is 10 times that of its pristine form. The strategy developed in our work can be generally applied for enhancing the ion storage capacity of metal chalcogenides ...

SiOx is a promising anode material for lithium-ion batteries (LIBs) due to its relatively high capacity. Nevertheless, the poor conductivity and large volume expansion of SiOx upon Li+ insertion/extraction limit its application. Herein, a novel strategy for preparing ternary Ni/SiOx/nitrogen-doped carbon (NSC) composites has been developed through in situ transformation of a Ni3Si2O5(OH)4/nitrogen-doped carbon precursor derived from dried bamboo leaves. The 3D interconnected SiOx/nitrogen-doped carbon (SC) framework provides sufficient void spaces for relieving the volume change during the lithiation process while facilitating electrolyte infiltration and lithium ion diffusion processes. The growth of uniform Ni nanoparticles (NPs) on the surface of the SC matrix restricts the formation of cracks, reduces volume expansion during the lithiation process, and effectively improves the electrical conductivity of SiOx. The optimized sample delivers a high discharge capacity of 864.6 mA h g−1 after 70 cycles at 200 mA g−1 and a superior rate capability of 289.8 mA h g−1 at 10 A g−1. The electrode delivers a capacity of 427.6 mA h g−1 even at 5 A g−1 after 1000 cycles along with outstanding capacity retention (∼100%). Our method provides insight into the utilization of biomass towards high performance energy storage through simple and low-cost procedures.

Flexible zinc ion batteries are a promising energy supply for flexible and wearable electronic devices due to their high theoretical capacity, superior safety, low cost, and eco-friendliness. The rational design of highly efficient flexible zinc ion batteries with high electrochemical performance, long cycling life, and excellent mechanical deformability is still a formidable challenge, limiting their widespread application in flexible electronics. This paper summarizes the recent progress in designing and fabricating flexible zinc ion batteries from three aspects: device configurations, battery constituent components, and practical applications. First, we introduce the energy storage mechanism and summarize modification strategies of constituent components, including current collector, zinc anode, cathode, and solid/gel electrolyte, revealing their positive effects on the performance of flexible zinc ion batteries. Then, we elucidate advanced device configurations for flexible zinc ion batteries such as sandwich-type, planar, and fiber-type structures, followed by discussion on the specific properties of flexible zinc ion batteries that enhance their adaptability in practical applications, such as integration with electronics, self-healing ability, resistance to extreme conditions, and responsiveness to environments. The current challenges and outlooks are also presented.

In this work, we systematically investigate and compare the activity of MnCo-based electrocatalysts (i.e. selenide, oxide, and hydroxide) for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline solutions. The result indicates that the selenides are oxidized upon OER and the surface generated oxides are the real OER active species. The MnCo selenides exhibit a significantly enhanced performance as compared to the oxide and hydroxide though the real active OER species of these three catalysts are essentially the same. The superior activity of MnCo selenides could be attributed to the high intrinsic conductivity and the high surface active area. Further, the synergy between Mn and Co lowers the energy barrier for catalysis and helps to stabilize the material. The bimetallic MnCo selenides with yolk shell structures possess the optimal electrochemical performance with a low cell voltage of 1.66 V at the current density of 50 mA cm−2, outperforming most of the earth-abundant electrocatalysts. Our work provides a better understanding of the active species of metal selenides and the origin of the performance disparity between selenides (-derived oxides) and oxides electrocatalysts.

Vanadium diselenide (VSe2) is a transition metal dichalcogenide with metallic conductivity, which makes it a potentially promising electrode material for electrochemical applications. However, the development of VSe2 electrodes for such applications has been severely hampered by the difficulty of preparing nanosized products. In this work, a new facile solvothermal synthesis process is developed and optimized to synthesize ultrathin VSe2 nanosheet assemblies. To obtain the ultrathin nanosheets, N-methyl pyrrolidone, which has similar surface energy to many transition metal dichalcogenides, was used as the solvent to limit the crystal growth along the c-axis direction. The resulting ultrathin VSe2 nanosheets exhibit good performance toward alkaline ion (Li+ and Na+) storage, which can be significantly enhanced by carbon coating. Specifically, the carbon-coated VSe2 nanosheets can deliver high capacities of 768 mA h g-1 (Li+ storage) and 571 mA h g-1 (Na+ storage) along with outstanding stability.

The performance of chemically intercalated V2O5 was found to strongly depend on the interlayer spacing, which is related to the radius of hydrated metal ion, which can be readily tuned by using different intercalated metals. We report a layered Mg2+-intercalated V2O5 as the cathode material for aqueous ZIBs. The large radius of hydrated Mg2+ (∼4.3 A, compared with 3.8 A of commonly used Li+) results in an interlayer spacing as large as 13.4 A (against 11.07 A for Li+-intercalated V2O5), which allows efficient Zn2+ (de)insertion. As a result, the obtained porous Mg0.34V2O5·0.84H2O cathodes work in a wide potential window of 0.1 to 1.8 V versus Zn2+/Zn, and can deliver high capacities of 353 and 264 mA h g–1 at current densities of 100 and 1000 mA g–1, respectively, along with long-term durability. Furthermore, the reversible Zn2+ (de)intercalation reaction mechanism is confirmed by multiple characterizations methods.

Developing advanced materials with high catalytic activity for electrocatalytic applications is of vital importance to mitigate the energy crisis. In this work, we for the first time report a novel method to prepare bimetallic vanadium‑molybdenum nitride (MoVN) thin films by magnetron co-sputtering and further demonstrate their applications for hydrogen evolution reaction (HER). When used as HER catalysts, the resulting MoVN thin film electrodes show superior electrocatalytic activity especially in alkaline electrolyte in contrast to bare VN and Mo2N, delivering a low overpotential of 108 mV to afford a current density of 10 mA cm−2, a Tafel slope of 60 mV dec−1, as well as excellent long-term durability. Most importantly, our study opens opportunities to explore new HER catalyst materials in the family of bimetallic transition metal nitrides. Keywords: Electrocatalytic activity, Bimetallic nitrides, Magnetron co-sputtering, Hydrogen evolution reaction

We report a phosphine (PH3) plasma activation strategy for significantly boosting the electrochemical performance of supercapacitor electrodes. Using Fe2O3 as a demonstration, we show that the plasma activation simultaneously improves the conductivity, creates atomic-scale vacancies (defects), as well as increases active surface area, and thus leading to a greatly enhanced performance with a high areal capacitance of 340 mF cm−2 at 1 mA cm−2, compared to 66 mF cm−2 of pristine Fe2O3. Moreover, the asymmetric supercapacitor devices based on plasma-activated Fe2O3 anodes and electrodeposited MnO2 cathodes can achieve a high stack energy density of 0.42 mW h cm−3 at a stack power density of 10.3 mW cm−3 along with good stability (88% capacitance retention after 9000 cycles at 10 mA cm−2). Our work provides a simple yet effective strategy to greatly enhance the electrochemical performance of Fe2O3 anodes and to further promote their application in asymmetric supercapacitors.

Metal-layered double hydroxides (LDHs), a family of versatile layered materials recently popular as earth-abundant oxygen evolution reaction (OER) catalysts, allow for both metal substitution and interlayer anion exchange without disrupting the two-dimensional (2D) crystal structure, although the ubiquity of carbonate anions is challenging to avoid. Here, we use hydrothermal synthesis in modified solvents with triethanolamine to directly synthesize bulk NiFe LDHs with carbonate, chloride, and sulfate interlayer anions without inert atmosphere protection. Structural characterizations by X-ray diffraction, infrared spectroscopy, and energy-dispersive X-ray spectroscopy confirm the anion composition. Electrochemical characterization shows that LDHs with these three anions display similar OER catalytic performance after surface area normalization, consistent with observed anion exchange to carbonate in alkaline electrolyte under ambient conditions. However, dodecyl sulfate-intercalated NiFe LDHs prepared by a...

Transition metal nitrides are regarded as a new class of excellent electrode materials for high-performance supercapacitors due to their superior chemical stability and excellent electrical conductivity. We synthesize successfully the porous CrN thin films for binder-free supercapacitor electrodes by reactive magnetron co-sputtering and selective chemical etching. The porous CrN thin film electrodes exhibit high-capacitance performance (31.3 mF cm−2 at 1.0 mA cm−2) and reasonable cycling stability (94% retention after 20000 cycles). Moreover, the specific capacitance is more than two-fold higher than that of the CrN thin film electrodes in previous work. In addition, a symmetric supercapacitor device with a maximum energy density of 14.4 mWh cm−3 and a maximum power density of 6.6 W cm−3 is achieved. These findings demonstrate that the porous CrN thin films will have potential applications in supercapacitors.

A series of graphitic-C3N4/ZnS (g-C3N4/ZnS) supercapacitor electrode materials have been prepared via a one-step calcination process of zinc acetate/thiourea with different mass ratios under nitrogen atmosphere. The optimized g-C3N4/ZnS composite shows a highest specific capacitance of 497.7 F/g at 1 A/g and good cycling stability with capacitance retention of 80.4% at 5 A/g after 1000 cycles. Moreover, g-C3N4/ZnS composites display an improved supercapacitor performance in terms of specific capacitance compared to the pure g-C3N4 and ZnS. In addition, our designed symmetric supercapacitor device based on g-C3N4/ZnS composite electrodes can exhibit an energy density of 10.4 Wh/kg at a power density of 187.3 W/kg. As a result, g-C3N4/ZnS composites are expected to be a prospective material for supercapacitors and other energy storage applications.

In this work, we demonstrate that the electrocatalytic activity of transition metal chalcogenides can be greatly enhanced by simultaneously engineering the active sites, surface area, and conductivity. Using metal-organic frameworks-derived (Ni,Co)Se 2 /C hollow rhombic dodecahedra (HRD) as a demonstration, we show that the incorporation of Ni into CoSe 2 could generates additional active sites, the hierarchical hollow structure promotes the electrolyte diffusion, the in-situ hybridization with C improves the conductivity. As a result, the (Ni,Co)Se 2 /C HRD exhibit superior performance toward the overall water-splitting electrocatalysis in 1 M KOH with a cell voltage as low as 1.58 V at the current density of 10 mA cm −2 , making the (Ni,Co)Se 2 /C HRD as a promising alternative to noble metal catalysts for water splitting.