Enhancing the performance of aqueous zinc ion battery cathodes with a floral spherical V5O12·6H2O/V6O13/CNT nanocomposite.

Aqueous zinc ion batteries (AZIBs) offer a promising approach for electrical energy storage, combining cost-effectiveness and enhanced thermal safety. However, the cathode material, vanadium oxide, while known for its excellent theoretical specific capacity, faces a challenge in terms of its poor electronic conductance. In this study, we present a novel strategy to address this limitation by constructing the V5O12·6H2O/V6O13/CNT (VOH/CNT) nanocomposite, resulting in significantly improved electrochemical performance. This nanocomposite was synthesized through a facile solvothermal method, yielding a unique floral spherical structure featuring a central cluster and multiple smaller groupings. The integration of CNTs into the composite significantly enhanced its electronic conductance, effectively mitigating the electronic conductance issue associated with vanadium oxide. Moreover, the composite retains crystalline water within its structure, playing a crucial role in providing a favorable ion-conductive pathway. Consequently, the VOH/CNT nanocomposite exhibits an impressive reversible capacity of 201 mA h g-1 at 50 mA g-1, surpassing that of VOH (116 mA h g-1). Remarkably, even at a high current density, the VOH/CNT nanocomposite demonstrates an exceptional capacity retention, maintaining a capacity of 150 mA h g-1 over 500 cycles at 1 A g-1. Its outstanding electrochemical performance can be attributed to its distinctive structural arrangement, the conductive network facilitated by CNTs, and the introduced crystalline water component.

Tetrahedral Bonding Structure (Ni3 -Se) Induced by Lattice-Distortion of Ni to Achieve High Catalytic Activity in Na-Se Battery.

Fabrication of transition-metal catalytic materials is regarded as a promising strategy for developing high-performance sodium-selenium (Na-Se) batteries. However, more systematic explorations are further demanded to find out how their bonding interactions and electronic structures can affect the Na storage process. This study finds that lattice-distorted nickel (Ni) structure can form different bonding structures with Na2 Se4 , providing high activity to catalyze the electrochemical reactions in Na-Se batteries. Using this Ni structure to prepare electrode (Se@NiSe2 /Ni/CTs) can realize rapid charge transfer and high cycle stability of the battery. The electrode exhibits high storage performance of Na+ ; i.e., 345 mAh g⁻1 at 1 C after 400 cycles, and 286.4 mAh g⁻1 at 10 C in rate performance test. Further results reveal the existence of a regulated electronic structure with upshifts of the d-band center in the distorted Ni structure. This regulation changes the interaction between Ni and Na2 Se4 to form a Ni3 -Se tetrahedral bonding structure. This bonding structure can provide higher adsorption energy of Ni to Na2 Se4 to facilitate the redox reaction of Na2 Se4 during the electrochemical process. This study can inspire the design of bonding structure with high performance in conversion-reaction-based batteries.

V-doped Ni2P nanoparticle grafted g-C3N4 nanosheets for enhanced photocatalytic hydrogen evolution performance under visible light.

Exploring low-cost and highly active photocatalysts with noble metal-free cocatalysts is of great significance for photocatalytic hydrogen evolution under simulated sunlight irradiation. In this work, a novel V-doped Ni2P nanoparticle loaded g-C3N4 nanosheet is reported as a highly efficient photocatalyst for H2 evolution under visible light irradiation. The results demonstrate that the optimized 7.8 wt% V-Ni2P/g-C3N4 photocatalyst exhibits a high hydrogen evolution rate of 271.5 µmol g-1 h-1, which is comparable to that of the 1 wt% Pt/g-C3N4 photocatalyst (279 µmol g-1 h-1), and shows favorable hydrogen evolution stability for five successive runs within 20 h. The remarkable photocatalytic hydrogen evolution performance of V-Ni2P/g-C3N4 is mainly due to the enhanced visible light absorption ability, the facilitated separation of photo-generated electron-hole pairs, the prolonged lifetime of photo-generated carriers and the fast transmission ability of electrons.

Fe, Ni-codoped W18O49 grown on nickel foam as a bifunctional electrocatalyst for boosted water splitting.

Designing cost-effective bifunctional catalysts with high-performance and durability is of great significance for renewable energy systems. Herein, typical Fe, Ni-codoped W18O49/NF was prepared via a simple solvothermal method. The incorporation of Fe ions enhanced the electronic interaction and enlarged the electrochemically active surface area. The increased W4+ leads to a high proportion of unsaturated W[double bond, length as m-dash]O bonds, thus enhancing the adsorption capacity of water. The valence configuration of nickel (Ni) sites in such dual-cation doping is well adjusted, realizing a high proportion of trivalent Ni ions (Ni3+). Due to the orbital interactions, the Fe3+/Ni3+ ions and OER reaction intermediates exhibit strong orbital overlap. The positions of the valence band and conduction band are well modulated. As a result, the Fe, Ni-codoped W18O49/NF shows improved electrocatalytic activity, and achieves a low decomposition voltage of 1.58 V at 10 mA cm-2 and retains long-time stability.

Realizing Fast Charge Diffusion in Oriented Iron Carbodiimide Structure for High-Rate Sodium-Ion Storage Performance.

Iron carbodiimide (FeNCN) belongs to a type of metal compounds with a more covalent bonding structure compared to common transition metal oxides. It could provide possibilities for various structural designs with improved charge-transfer kinetics in battery systems. Moreover, these possibilities are still highly expected for promoting enhancement in rate performance of sodium (Na)-ion battery. Herein, oriented FeNCN crystallites were grown on the carbon-based substrate with exposed {010} faces along the [001] direction (O-FeNCN/S). It provides a high Na-ion storage capacity with excellent rate capability (680 mAh g-1 at 0.2 A g-1 and 360 mAh g-1 at 20 A g-1), presenting rapid charge-transfer kinetics with high contribution of pseudocapacitance during a typical conversion reaction. This high rate performance is attributed to the oriented morphology of FeNCN crystallites. Its orientation along [001] maintains preferred Na-ion diffusion along the two directions in the entire morphology of O-FeNCN/S, supporting fast Na-ion storage kinetics during the charge/discharge process. This study could provide ideas toward the understanding of the rational structural design of metal carbodiimides for attaining high electrochemical performance in future.

Layered-structure (NH4)2Mo4O13@N-doped porous carbon composite as a superior anode for lithium-ion batteries.

A novel (NH4)2Mo4O13/N-doped porous carbon composite is fabricated in situ using a one-step solid technique. Benefiting from the intriguing features of this composite, it undergoes an intercalation and conversion reaction mechanism with diffusion-controlled Li storage behaviour, exhibiting an excellent reversible capacity of 1151 mA h g-1 over 350 cycles.

Generation of Ni3S2 nanorod arrays with high-density bridging S22- by introducing a small amount of Na3VO4·12H2O for superior hydrogen evolution reaction.

Bridging S22- moieties have been demonstrated to be highly active sites existing in metal polysulfides for the hydrogen evolution reaction (HER), thus the incorporation of high-density bridging S22- into a Ni3S2 material to improve its electrocatalytic HER performance is highly desirable and challenging. Herein, we report a novel Ni3S2 nanorod array decorated with (020)-oriented VS4 nanocrystals grown on nickel foam (Shig-NS-rod/NF) via a simple and facile solvothermal method. Results show that the in situ incorporation of VS4 not only triggers the formation of such a nanorod array structure, but also contributes to the uniform grafting of high-density and high catalytically active bridging S22- sites on the interface between Ni3S2 and VS4 for enhanced HER activity, and also promotes the absorption ability of OH- radicals and thus accelerates the HER Volmer step in alkaline media. As expected, the resultant Shig-NS-rod/NF material exhibits impressive catalytic performance toward the HER, with a much lower overpotential of 137 mV at 10 mA cm-2 and a long-term durability for at least 22 h, and is superior to Ni3S2 nanorod arrays with low-density bridging S22- (Slow-NS-rod/NF) and NS-film/NF counterparts (without VS4), even outperforming the NF-supported 20% Pt/C at a large current density of over 120 mA cm-2. Our findings put forward fresh insight into the rational design of highly efficient electrocatalysts toward the HER for green hydrogen fuel production.

Methanol-assisted synthesis of Ni3+-doped ultrathin NiZn-LDH nanomeshes for boosted alkaline water splitting.

The construction of nanoporous structure combined with the optimization of electronic structure toward electrocatalysts could be a promising and effective approach to boosting their catalytic performance. Herein, we rationally synthesized a novel Ni3+-doped ultrathin NiZn layered double hydroxide nanomesh supported on nickel foam (Ni(ii,iii)Zn-LDH/NF-nm) by a facile one-step methanol-assisted hydrothermal method. Results show that methanol can not only trigger the generation of ultrathin nanomesh structure, but adjust portion of Ni2+ to Ni3+ and thus to result in the Ni3+-doped NiZn-LDH nanomesh material. The nanoporous feature endows Ni(ii,iii)Zn-LDH/NF-nm with abundant exposed catalytic active sites and fast mass transfer for alkaline water electrolysis. More importantly, the Ni3+ doping can facilitate the available formation of highly active NiOOH phase on the surface for the oxygen evolution reaction (OER), accompanied by increased oxygen vacancies that can greatly enhance the electronic conductivity, leading to the improved intrinsic activity and the accelerated electrocatalytic OER reaction kinetics. As expected, the as-prepared Ni(ii,iii)Zn-LDH/NF-nm has relatively low overpotentials of 320 and 370 mV to drive large current densities of 100 and 500 mA cm-2, respectively, and a small Tafel slope of 63.9 mV dec-1, extremely superior to RuO2/NF and NiZn-LDH/NF-ns counterpart. Meanwhile, the electrolyzer assembled for overall water splitting by Ni(ii,iii)Zn-LDH/NF-nm yields the outstanding catalytic activity and stability. This work highlights a feasible strategy to design and develop high-efficiency water splitting electrocatalysts via engineering on composition and nanostructure.

Boosting the activity of Prussian-blue analogue as efficient electrocatalyst for water and urea oxidation.

The design and fabrication of intricate hollow architectures as cost-effective and dual-function electrocatalyst for water and urea electrolysis is of vital importance to the energy and environment issues. Herein, a facile solvothermal strategy for construction of Prussian-blue analogue (PBA) hollow cages with an open framework was developed. The as-obtained CoFe and NiFe hollow cages (CFHC and NFHC) can be directly utilized as electrocatalysts towards oxygen evolution reaction (OER) and urea oxidation reaction (UOR) with superior catalytic performance (lower electrolysis potential, faster reaction kinetics and long-term durability) compared to their parent solid precursors (CFC and NFC) and even the commercial noble metal-based catalyst. Impressively, to drive a current density of 10 mA cm-2 in alkaline solution, the CFHC catalyst required an overpotential of merely 330 mV, 21.99% lower than that of the solid CFC precursor (423 mV) at the same condition. Meanwhile, the NFHC catalyst could deliver a current density as high as 100 mA cm-2 for the urea oxidation electrolysis at a potential of only 1.40 V, 24.32% lower than that of the solid NFC precursor (1.85 V). This work provides a new platform to construct intricate hollow structures as promising nano-materials for the application in energy conversion and storage.

Co,N-Codoped porous vanadium nitride nanoplates as superior bifunctional electrocatalysts for hydrogen evolution and oxygen reduction reactions.

Developing efficient and low-cost bifunctional electrocatalysts as candidates for Pt-based materials to satisfy commercial applications in the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is still very challenging. Herein, we show that Co,N-codoped porous vanadium nitride (VCoN) nanoplates are successfully synthesized via a simple one-step pyrolysis protocol without the use of NH3 gas. We also demonstrate that the crystallization, surface chemical state and porosity of vanadium nitride are well modulated by inventively using Co dopants as structural inducers. The resulting VCoN material exhibits an excellent catalytic activity towards the HER in alkaline media, with an extremely low onset potential of -0.03 V, an overpotential of 179 mV at 10 mA cm-2, and a remarkable durability for over 100 h. Moreover, it shows a superior ORR performance, which compares favorably with commercial 20% Pt/C, exhibiting an onset potential of ∼1.02 V, a half-wave potential of ∼0.91 V and a weak potential shift (-5 mV) after 2000 cycles at 1600 rpm in 0.1 M KOH. Such excellent electrocatalytic performance primarily contributes to the unique structural features of the heteroatom N (pyrrolic and graphitic N) and Co codoping in favor of improving the electrical conductivity and the high porosity contributing to exposing numerous catalytic active sites.