Optimizing electronic structure of porous Ni/MoO2 heterostructure to boost alkaline hydrogen evolution reaction

Ru-regulated electronic structure CoNi-MOF nanosheets advance water electrolysis kinetics in alkaline and seawater media

Herein, an ion-exchange strategy is utilized to greatly improve the kinetics of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by Ru-modified CoNi- 1,3,5-Benzenetricarboxylic acid (BTC)-metal organic framework nanosheets (Ru@CoNi-MOF). Due to the higher Ni active sites and lower electron transfer impedance, Ru@CoNi-MOF catalyst requires the overpotential as low as 47 and 279 mV, at a current density of 10 mA/cm2 toward HER and OER, respectively. Significantly, the mass activity of Ru@CoNi-MOF for HER and OER are 25.9 and 10.6 mA mg-1, nearly 15.2 and 8.8 times higher than that of Ni-MOF. In addition, the electrolyzer of Ru@CoNi-MOF demonstrates exceptional electrolytic performance in both KOH and seawater environment, surpasses the commercial Pt/C||IrO2 couple. Theoretical calculations prove that introducing Ru atoms in - CoNi-MOF modulates the electronic structure of Ni, optimizes adsorption energy for H* and reduces energy barrier of metal organic frameworks (MOFs). This modification significantly improves the kinetic rate of the Ru@CoNi-MOF during water splitting. Certainly, this study highlights the utilization of MOF nanosheets as advanced HER/OER electrocatalysts with immense potential, and will paves a way to develop more efficient MOFs for catalytic applications.

Spark plasma sintered porous Ni as a novel substrate of Ni3Se2@Ni self-supporting electrode for ultra-durable hydrogen evolution reaction

Developing efficient and durable self-supporting catalytic electrodes is an important way for industrial applications of hydrogen evolution reaction. Currently, commercial nickel foam (NF)-based electrode has been widely used due to its good catalytic performance. However, the NF consisting of smooth skeleton surface and large pores not only exhibits poor conductivity but also provides insufficient space for catalyst decoration and sufficient adhesion, resulting in inadequate catalytic performance and poor durability of NF-based electrodes. In this paper, a novel three-dimensional porous Ni substrate with multangular skeleton surface and small pore structure was prepared by a modified spark plasma sintering technique, and subsequently Ni3Se2@Porous Ni electrode with a large number of Ni3Se2 nanosheets uniformly distributed on the surface was obtained by one-step in-situ selenization. The electrode exhibits outstanding conductivity and catalytic hydrogen evolution reaction, providing a low overpotential of 183 mV at a current density of 100 mA cm-2. Due to the strong interfacial bonding between Ni and Ni3Se2, the Ni3Se2@Porous Ni electrode shows strong durability, which can work stably at 85 mA cm-2 for more than 200 h. This work provides an effective strategy for the rational preparation of metal substrates for efficient and durable self-supporting catalytic electrodes.

Interfacial Modulation of a Self-Sacrificial Synthesized SnO2@Sn Core-Shell Heterostructure Anode toward High-Capacity Reversible Li+ Storage

Sn-based anodes are promising high-capacity anode materials for low-cost lithium ion batteries. Unfortunately, their development is generally restricted by rapid capacity fading resulting from large volume expansion and the corresponding structural failure of the solid electrolyte interphase (SEI) during the lithiation/delithiation process. Herein, heterostructural core-shell SnO2-layer-wrapped Sn nanoparticles embedded in a porous conductive nitrogen-doped carbon (SOWSH@PCNC) are proposed. In this design, the self-sacrificial Zn template from the precursors is used as the pore former, and the LiF-Li3N-rich SEI modulation layer is motivated to average uniform Li+ flux against local excessive lithiation. Meanwhile, both the chemically active nitrogen sites and the heterojunction interfaces within SnO2@Sn are implanted as electronic/ionic promoters to facilitate fast reaction kinetics. Consequently, the as-converted SOWSH@PCNC electrodes demonstrate a significantly boosted Li+ capacity of 961 mA h g-1 at 200 mA g-1 and excellent cycling stability with a low capacity decaying rate of 0.071% after 400 cycles at 500 mA g-1, suggesting their great promise as an anode material in high-performance lithium ion batteries.

Synthesis of Flower-Like Cobalt-Molybdenum Mixed-Oxide Microspheres for Deep Aerobic Oxidative Desulfurization of Fuel

Flower-like cobalt-molybdenum mixed-oxide microspheres (CoMo-FMs) with hierarchical architecture were successfully synthesized via a hydrothermal process and subsequent calcination step. The characterization results show that CoMo-FMs were assembled from ultrathin mesoporous nanosheets with thicknesses of around 4.0 nm, providing the composite with a large pore volume and a massive surface area. The synthesized CoMo-FMs were employed as catalysts for the aerobic oxidative desulfurization (AODS) of fuel, and the reaction results show that the optimal catalyst (CoMo-FM-2) demonstrated an outstanding catalytic performance. Over CoMo-FM-2, various thiophenic sulfides could be effective removed at 80-110 °C under an atmospheric pressure, and a complete conversion of sulfides could be achieved in at least six consecutive cycles without a detectable change in chemical compositions. Further, the catalytic mechanism was explored by conducting systemic radical trapping and transformation experiments, and the excellent catalytic performance for CoMo-FMs should be mainly due to the synergistic effect of Mo and Co elements.

Caffeic Acid-Zinc Basic Salt/Chitosan Nanohybrid Possesses Controlled Release Properties and Exhibits In Vivo Anti-Inflammatory Activities

Caffeic acid (CA) exhibits a myriad of biological activities including cardioprotective action, antioxidant, antitumor, anti-inflammatory, and antimicrobial properties. On the other hand, CA presents low water solubility and poor bioavailability, which have limited its use for therapeutic applications. The objective of this study was to develop a nanohybrid of zinc basic salts (ZBS) and chitosan (Ch) containing CA (ZBS-CA/Ch) and evaluate its anti-edematogenic and antioxidant activity in dextran and carrageenan-induced paw edema model. The samples were obtained by coprecipitation method and characterized by X-ray diffraction, Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and UV-visible spectroscopy. The release of caffeate anions from ZBS-CA and ZBS-CA/Ch is pH-dependent and is explained by a pseudo-second order kinetics model, with a linear correlation coefficient of R² ≥ 0.99 at pH 4.8 and 7.4. The in vivo pharmacological assays showed excellent anti-edematogenic and antioxidant action of the ZBS-CA/Ch nanoparticle with slowly releases of caffeate anions in the tissue, leading to a prolongation of CA-induced anti-edematogenic and anti-inflammatory activities, as well as improving its inhibition or sequestration antioxidant action toward reactive species. Overall, this study highlighted the importance of ZBS-CA/Ch as an optimal drug carrier.

Efficient Regulation of Polysulfides by Anatase/Bronze TiO2 Heterostructure/Polypyrrole Composites for High-Performance Lithium-Sulfur Batteries

Despite having ultra-high theoretical specific capacity and theoretical energy density, lithium-sulfur (Li-S) batteries suffer from their low Coulombic efficiency and poor lifespan, and the commercial application of Li-S batteries is seriously hampered by the severe "shuttle effect" of lithium polysulfides (LiPSs) and the large volume expansion ratio of the sulfur electrode during cycling. Designing functional hosts for sulfur cathodes is one of the most effective ways to immobilize the LiPSs and improve the electrochemical performance of a Li-S battery. In this work, a polypyrrole (PPy)-coated anatase/bronze TiO₂ (TAB) heterostructure was successfully prepared and used as a sulfur host. Results showed that the porous TAB could physically adsorb and chemically interact with LiPSs during charging and discharging processes, inhibiting the LiPSs' shuttle effect, and the TAB's heterostructure and PPy conductive layer are conducive to the rapid transport of Li⁺ and improve the conductivity of the electrode. By benefitting from these merits, Li-S batteries with TAB@S/PPy electrodes could deliver a high initial capacity of 1250.4 mAh g^-1 at 0.1 C and show an excellent cycling stability (the average capacity decay rate was 0.042% per cycle after 1000 cycles at 1 C). This work brings a new idea for the design of functional sulfur cathodes for high-performance Li-S battery.

Single-Atom Phosphorus Defects Decorated CoP Cocatalyst Boosts Photocatalytic Hydrogen Generation Performance of Cd0.5 Zn0.5 S by Directed Separating the Photogenerated Carriers

Design and preparation of an efficient and nonprecious cocatalysts, with structural features and functionality necessary for improving photocatalytic performance of semiconductors, remain a formidable challenge until now. Herein, for the first time, a novel CoP cocatalyst with single-atom phosphorus vacancies defects (CoP-V_p ) is synthesized and coupled with Cd_0.5 Zn_0.5 S to build CoP-V_p @Cd_0.5 Zn_0.5 S (CoP-V_p @CZS) heterojunctions photocatalysts via a liquid phase corrosion method following by an in suit growth process. The nanohybrids deliver an attractive photocatalytic hydrogen production activity of 2.05 mmol h^-1 30 mg^-1 under visible-light irradiation, which is 14.66 times higher than that of the pristine ZCS samples. As expected, CoP-V_p further enhances the charge-separation efficiency of ZCS, in addition to the improvement of the electron transfer efficiency, which is confirmed by the ultrafast spectroscopies. Mechanism studies based on density functional theory calculations verify that Co atoms adjacent with single-atom V_p play the key role in translation, rotation, and transformation of electrons for H₂ O reduction. This scalable strategy focusing defect engineering provides a new insight into designing the highly active cocatalysts to boost the photocatalytic application.

Realizing Ultrafast and Robust Sodium-Ion Storage of Iron Sulfide Enabled by Heteroatomic Doping and Regulable Interface Engineering

Fe-based sulfides are a promising type of anode material for sodium-ion batteries (SIBs) due to their high theoretical capacities and affordability. However, these materials often suffer from issues such as capacity deterioration and poor conductivity during practical application. To address these challenges, an N-doped Fe₇S₈ anode with an N, S co-doped porous carbon framework (PPF-800) was synthesized using a template-assisted method. When serving as an anode for SIBs, it delivers a robust and ultrafast sodium storage performance, with a discharge capacity of 489 mAh g^-1 after 500 cycles at 5 A g^-1 and 371 mAh g^-1 after 1000 cycles at 30 A g^-1 in the ether-based electrolyte. This impressive performance is attributed to the combined influence of heteroatomic doping and adjustable interface engineering. The N, S co-doped carbon framework embedded with Fe₇S₈ nanoparticles effectively addresses the issues of volumetric expansion, reduces the impact of sodium polysulfides, improves intrinsic conductivity, and stimulates the dominant pseudocapacitive contribution (90.3% at 2 mV s^-1). Moreover, the formation of a stable solid electrolyte interface (SEI) film by the effect of uniform pore structure in ether-based electrolyte produces a lower transfer resistance during the charge-discharge process, thereby boosting the rate performance of the electrode material. This work expands a facile strategy to optimize the electrochemical performance of other metal sulfides.

Synergistic Effect of N-NiMoO4 /Ni Heterogeneous Interface with Oxygen Vacancies in N-NiMoO4 /Ni/CNTs for Superior Overall Water Splitting

The exploring of economical, high-efficiency, and stable bifunctional catalysts for hydrogen evolution and oxygen evolution reactions (HER/OER) is highly imperative for the development of electrolytic water. Herein, a 3D cross-linked carbon nanotube supported oxygen vacancy (V_o )-rich N-NiMoO₄ /Ni heterostructure bifunctional water splitting catalyst (N-NiMoO₄ /Ni/CNTs) is synthesized by hydrothermal-H₂ calcination method. Physical characterization confirms that V_o -rich N-NiMoO₄ /Ni nanoparticles with an average size of ≈19 nm are secondary aggregated on CNTs that form a hierarchical porous structure. The formation of Ni and NiMoO₄ heterojunctions modify the electronic structure of N-NiMoO₄ /Ni/CNTs. Benefiting from these properties, N-NiMoO₄ /Ni/CNTs drives an impressive HER overpotential of only 46 mV and OER overpotential of 330 mV at 10 mA cm^-2 , which also shows exceptional cycling stability, respectively. Furthermore, the as-assembled N-NiMoO₄ /Ni/CNTs||N-NiMoO₄ /Ni/CNTs electrolyzer reaches a cell voltage of 1.64 V at 10 mA cm^-2 in alkaline solution. Operando Raman analysis reveals that surface reconstruction is essential for the improved catalytic activity. Density functional theory (DFT) calculations further demonstrate that the enhanced HER/OER performance should be attributed to the synergistic effect of V_o and heteostructure that improve the conductivity of N-NiMoO₄ /Ni/CNTs and facilitatethe desorption of reaction intermediates.

Soft-template derived Ni/Mo2C hetero-sheet arrays for large current density hydrogen evolution reaction

Practical structural design and electronic regulation are significant for synthesising efficient electrocatalysts. Therefore, a facile soft-template approach has been applied to successfully grow Ni/Mo₂C heterojunction nanosheet arrays on nickel foam (NF) skeleton (NS-Ni/Mo₂C@NF) using polyvinylpyrrolidone (PVP) as a soft template. The density functional theory (DFT) calculations reveal that abundant Ni/Mo₂C heterojunction in NS-Ni/Mo₂C@NF can provide many active sites with a moderate hydrogen adsorption free energy (ΔG_H*, 0.037 eV). Benefiting from this nanosheet array structure and abundant Ni/Mo₂C heterojunctions, the NS-Ni/Mo₂C@NF catalyst can efficiently catalyze HER, especially at large current densities. As a result, only 151 and 271 mV overpotentials are needed to deliver 100 and 1000 mA/cm² HER, respectively. More importantly, the hydrogen production testing with NS-Ni/Mo₂C@NF as the working electrode can run stably for 500 h without activity decay under the current density of 500 mA/cm² commonly used in industrial water electrolyzers, indicating that NS-Ni/Mo₂C@NF has broad application prospects.

Induced Bimetallic Sulfide Growth with Reduced Graphene Oxide for High-Performance Sodium Storage

Metal sulfide has been considered an ideal sodium-ion battery (SIB) anode material based on its high theoretical capacity. Nevertheless, the inevitable volume expansion during charge-discharge processes can lead to unsatisfying electrochemical properties, which limits its further large-scale application. In this contribution, laminated reduced graphene oxide (rGO) successfully induced the growth of SnCoS₄ particles and self-assembled into a nanosheet-structured SnCoS₄@rGO composite through a facile solvothermal procedure. The optimized material can provide abundant active sites and facilitate Na⁺ ion diffusion due to the synergistic interaction between bimetallic sulfides and rGO. As the anode of SIBs, this material maintains a high capacity of 696.05 mAh g^-1 at 100 mA g^-1 after 100 cycles and a high-rate capability of 427.98 mAh g^-1 even at a high current density of 10 A g^-1. Our rational design offers valuable inspiration for high-performance SIB anode materials.

Electronic redistribution over the active sites of NiWO4-NiO induces collegial enhancement in hydrogen evolution reaction in alkaline medium

The activity-enhancement of a new-generation catalyst focuses on the collegial approach among specific solids which exploit the mutual coactions of these materials for HER applications. Strategic manipulation of these solid interfaces typically reveals unique electronic states different from their pure phases, thus, providing a potential passage to create catalysts with excellent activity and stability. Herein, the formation of the NiWO₄-NiO interface has been designed and synthesized via a three-step method. This strategy enhances the chance of the formation of abundant heterointerfaces due to the fine distribution of NiWO₄ nanoparticles over Ni(OH)₂ sheets. NiWO₄-NiO has superior HER activity in an alkaline (1 M KOH) electrolyte with modest overpotentials of 68 mV at 10 mA cm^-2 current density. The catalyst is highly stable in an alkaline medium and negligible change was observed in the current density even after 100 h of continuous operation. This study explores a unique method for high-performance hydrogen generation by constructing transition metal-oxides heterojunction. The XPS studies reveal an electronic redistribution driven by charge transfer through the NiWO₄-NiO interface. The density functional theory (DFT) calculations show that the NiWO₄-NiO exhibits a Pt-like activity with the hydrogen Gibbs free energy (ΔG_H*) value of 0.06 eV compared to the Pt(ΔG_H* = -0.02 eV).

NiCu alloys anchored Co3O4 nanowire arrays as efficient hydrogen evolution electrocatalysts in alkaline and neutral media

Robust and long-lasting non-precious metal electrocatalysts are essential to achieve sustainable hydrogen production. In this work, we synthesized Co₃O₄@NiCu by electrodepositing NiCu nanoclusters onto Co₃O₄ nanowire arrays that were formed in situ on nickel foam. The introduction of NiCu nanoclusters altered the inherent electronic structure of Co₃O₄, significantly increasing the exposure of active sites and enhancing endogenous electrocatalytic activity. Co₃O₄@NiCu exhibited overpotentials of only 20 and 73 mV, respectively, at 10 mA cm^-2 current densities in alkaline and neutral media. These values were equivalent to those of commercial Pt catalysts. Finally, the electron accumulation effect at the Co₃O₄@NiCu, along with a negative shift in the d-band center, is finally revealed by theoretical calculations. Hydrogen adsorption on consequent electron-rich Cu sites was effectively weakened, leading to a robust catalytic activity for the hydrogen evolution reaction (HER). Overall, this study proposes a practical strategy for creating efficient HER electrocatalysts in both alkaline and neutral media.