Insight into selenium vacancies enhanced CoSe2/MoSe2 heterojunction nanosheets for hydrazine-assisted electrocatalytic water splitting

Sub-3 nm 1 T-MoS2 self-supported nanosheets with fast ion transport and bubble release for membrane-free water electrolysis

Conventional water splitting is restricted by costly membrane electrode assemblies and a sluggish oxygen evolution reaction (OER) occurring at the anode. In light of this, the construction of a membrane-free water electrolysis system via a hydrazine-assisted seawater hydrogenation strategy surmounts both of these obstacles. Herein, we propose a new strategy to synthesize two-dimensional (2D) ultrathin porous 1 T-MoS2 (1 T-MoS2-10 %/CC), which consists of 2.3 nm triple-layer crystalline surface and has nano pores (2-4 nm). Due to the uniform and consistent nanosheet arrays composed of ultrathin large-layer-spacing nanosheets and abundant pores, the electrolyte and the 1 T-MoS2-10 %/CC can be fully contacted, showing superhydrophilicity, and increasing the bubble contact angle to release bubbles in time, showing superaerophobicity. Therefore, the special structure of 1 T-MoS2 shows advantageous for gas precipitation reaction-hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR), which require only 55 mV overpotential for HER and 7 mV (vs. RHE) working potential for HzOR to achieve a current density of 10 mA cm-2. In addition, we constructed a hybrid seawater membrane-free electrolysis system in which a current density of 100 mA cm-2 can be achieve with a cell voltage of only 0.27 V, which not only effectively replaces the high-energy-consuming OER for energy-saving hydrogen production, but also avoids the electrochemical reaction of chlorine evolution reaction (ClER) with the low cell voltage.

Applications, performance enhancement strategies and prospects of NixPy in electrocatalysis

Developing low-cost and high-efficiency electrocatalysts is the key to making energy-related electrocatalytic technologies commercially feasible. In recent years, nickel phosphide (NixPy) electrocatalysts have received extensive attention due to their multiple active sites, adjustable structure and composition, and unique physicochemical properties. In this review, the latest progress of NixPy in the field of electrocatalysis is reviewed from the aspects of the properties of NixPy, different synthesis methods, and ingenious modulation strategies. The significant enhancement effects of elemental doping, vacancy defect, interfacial engineering, synergistic effect, and the external magnetic field excitation-enhanced strategy on the electrocatalytic performance of NixPy are emphasized, Moreover, a forward-looking outlook for its future development direction is provided. Finally, some basic problems and research directions of NixPy in high-efficiency energy electrocatalysis are presented.

Interfacial-Free-Water-Enhanced Mass Transfer to Boost Current Density of Hydrogen Evolution

The advancement of water electrolysis highlights the growing importance of electrolyzers capable of operating at high current densities, where mass transfer dynamics plays a crucial role. In the electrode reactions, the interfacial water is a key factor in regulating these dynamics. However, the potential of utilizing interfacial-free water (IFW) to modulate electrode behavior remains underexplored. Herein, we investigate the effect of interfacial water structure on hydrogen evolution reaction (HER) performance across different current density ranges, using designed platinum-coated nickel hydroxide on nickel foam (Pt@Ni(OH)2-NF) electrodes. We reveal that with increasing current density, changes in interfacial water structure alter the rate-determining step of the HER. Pt@Ni(OH)2-NF exhibited excellent performance in alkaline electrolytes, achieving 1000 mA cm-2 at 114 mV overpotential. This study provides a novel approach to optimizing alkaline water electrolysis dynamics by enhancing mass transfer, further paving the way for more efficient and energy-saving hydrogen production.

Functionalized 3D Mo2N Current Collectors Drive Multi-Phase Ni-based Synergy and Mitigate Surface Reconstruction for Enhanced Oxygen Evolution Catalysis

Electrochemical water splitting is a promising approach for sustainable hydrogen production, but the oxygen evolution reaction (OER) remains a bottleneck due to sluggish kinetics, poor activity, and limited stability and scalability. Here, a Mo2N-functionalized nickel is designed foam (NF@Mo2N) and subsequently transform into a Mo2N/NiSe/Ni2P multi-phase heterostructure through selenization and phosphorization, to address these challenges. The optimized NF@Mo2N/NiSe/Ni2P catalyst integrates three key strategies: (I) functionalizing NF with Mo2N to enhance conductivity and charge transfer, (II) engineering a collaborative multi-interface heterostructure to optimize active sites and reaction kinetics, and (III) precisely controlling phase formation through selenization and phosphorization to mitigate surface reconstruction and ensure long-term stability. The catalyst not only achieves an overpotential of 242 mV@10 mA cm-2 and remarkable stability over 350 h, but also achieves a low overpotential of 395 mV at a high current density of 800 mA cm-2, outperforming the pristine other control samples. Theoretical analysis reveals that the Mo2N-stabilized NiSe/Ni2P heterostructure on NF enhances conductivity and optimizes adsorption energies of OER intermediates, leading to improved catalytic performance and stability. This work provides a new strategy for designing high-performance, non-precious metal OER catalysts for industrial applications and advancing sustainable hydrogen production.

Selenium-vacancy-mediated NiCoSe nanoplatforms with NIR-II amplified nanozymes for methicillin-resistant Staphylococcus aureus-infected pneumonia

The clinical management of bacterial pneumonia (BP) induced by multidrug-resistant (MDR) pathogens poses substantial therapeutic challenges, necessitating urgent development of novel antibacterial agents and treatment paradigms, particularly those targeting deep-tissue biofilms. While reactive oxygen species (ROS)-mediated nanozyme-catalyzed therapy represents a promising therapeutic strategy, its effectiveness remains limited by the suboptimal nanozyme biocatalytic efficiency and restricted therapeutic efficacy of monomodal approaches. To address these challenges, we engineered selenium vacancy-enriched nickel-cobalt selenide (NiCoSe) nanoplatforms demonstrating dual functional capabilities: exceptional biocatalytic performance and superior photothermal conversion efficiency within the second near-infrared window (NIR-II). Systematic evaluations revealed that the NiCoSe platform facilitates robust ROS generation, achieving potent bactericidal effects while synergistically accelerating biofilm eradication through NIR-II photothermal activation. This combined therapeutic modality establishes NiCoSe as a promising candidate for anti-infective treatment of MDR-BP. Our findings not only present an innovative strategy for combating deep-seated bacterial infections but also advance the translational potential of nanozyme-based therapeutics in clinical nanomedicine.

Vacancy and Dopant Co-Constructed Active Microregion in Ru-MoO3- x/Mo2AlB2 for Enhanced Acidic Hydrogen Evolution

Accurate identification of catalytic active regions is crucial for the rational design and construction of hydrogen evolution catalysts as well as the targeted regulation of their catalytic performance. Herein, the low crystalline-crystalline hybrid MoO3- x/Mo2AlB2 with unsaturated coordination and rich defects is taken as the precursor. Through the Joule heating reaction, the Ru-doped MoO3- x/Mo2AlB2 catalyst is successfully constructed. Building on the traditional view that individual atoms or vacancies act as active sites, this article innovatively proposes the theory that vacancies and doped atoms synergistically construct active microregions, and multiple electron-rich O atoms within the active microregions jointly serve as hydrogen evolution active sites. Based on X-ray absorption fine structure analysis and first-principles calculations, there is a strong electron transfer among Ru atoms, Mo atoms, and O atoms, leading to extensive O atoms with optimized electronic structure in the active microregions. These O atoms exhibit an H* adsorption free energy close to zero, thereby enhancing the catalytic activity for hydrogen evolution. This work provides a brand-new strategy for the design and preparation of electrocatalytic materials and the systematic regulation of the local electronic structure of catalysts.

Superhydrophilicity and superaerophobicity Ni/Ni3S4/1T-MoS2 for hydrazine-assisted seawater splitting

The overall hydrazine splitting (OHzS) is a promising strategy to achieve the efficient hydrogen production in seawater through replacing the slow kinetic oxygen evolution reaction (OER) and toxic chlorine evolution reaction (ClOR) by hydrazine oxidation (HzOR). We report an efficient bifunctional electrocatalyst of Ni/Ni3S4/1T-MoS2 on carbon cloth (Ni/Ni3S4/1T-MoS2/CC), which was formed from large layer spacing MoS2 and Ni3S4 with metal-Ni, and was applied as for both hydrogen evolution reaction (HER) and HzOR. The MoS2 had expanded interlayer spacing and showed 1T phase, with significantly improved conductivity and hydrophilicity, which promotes transfer process of reactants. Furthermore, the introduction of Ni/Ni3S4 on the 1T-MoS2 base surface leaded to superhydrophilic and superaerophobic properties, which makes it more conducive to the adsorption of H. The improvement of electrical conductivity induced the excellent HER and HzOR electrocatalytic properties of Ni/Ni3S4/1T-MoS2/CC, which showed an ultralow overpotential of 24 mV and working potential of 0 mV at a current density of 10 mA cm-2, respectively. Inspiringly, Ni/Ni3S4/1T-MoS2/CC also showed excellent performance in hydrazine-assisted alkaline seawater electrolysis, as well as solar panel powered electrolysis of seawater OHzS, therefore, exhibiting great potential for practical applications.

Dandelion-like VSe2-embellished CuSe-Co3Se4 hollow nanotube clusters as bifunctional catalysts for high-performance alkaline hydrogen evolution and solar cells

Among the various non-precious metal catalysts that drive hydrogen evolution reactions (HERs) and dye-sensitized solar cells (DSSCs), transition metal selenides (TMSs) stand out due to their unique electronic properties and tunable morphology. Herein, the multicomponent selenide CuSe-Co3Se4@VSe2 was successfully synthesized by doping with metal element vanadium and selenization on the copper-cobalt carbonate hydroxide (CuCo-CH) template. CuSe-Co3Se4@VSe2 exhibited the dandelion-like cluster structure composed of hollow nanotubes doped with VSe2 nanoparticles. Due to the unique structure and the synergistic effect of various elements, CuSe-Co3Se4@VSe2 showed excellent alkaline HER and DSSC performances. The DSSC based on CuSe-Co3Se4@VSe2 exhibited an impressive power conversion efficiency (PCE) of 9.64 %, which was much higher than that of Pt (8.39 %). Besides, it possessed a low HER overpotential of 76 mV@10 mA cm-2 and a small Tafel slope of 88.9 mV dec-1 in 1.0 M KOH.

Modulation of Charge Redistribution in Heterogeneous CoSe-Ni0.95Se Coupling with Ti3C2Tx MXene for Hydrazine-Assisted Water Splitting

Integrating abundant dual sites of hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER) into one catalyst is extremely urgent toward energy-saving H2 production. Herein, CoSe-Ni0.95Se heterostructure coupling with Ti3C2Tx MXene (CoSe-Ni0.95Se/MXene) is fabricated on nickel foam (NF) to enhance the catalytic performance. The heterogeneous CoSe-Ni0.95Se and MXene coupling effect can change the coordination of Ni and Co, resulting in adjusted interfacial electronic field and enhanced electron transfer from Ni0.95Se to CoSe especially near MXene surface. Also, the appearance of MXene can anchor more active sites, thereby abundant nucleophilic CoSe and electrophilic Ni0.95Se are formed induced by the charge redistribution, which can tailor d-band center, moderate *H adsorption free energy (∆GH *) and facilitate adsorption/desorption for hydrazine intermediates, contributing to much enhanced HER and HzOR performance. For example, the low potentials of -160.8 and 116.1 mV at 400 mA cm-2 are seen for HER and HzOR with long-term stability of 7 days. When assembled as overall hydrazine splitting (OHzS), a small cell voltage of 0.35 V to drive 100 mA cm-2 is obtained. Such concept of integrating abundant nucleophilic and electrophilic dual sites and regulating their d-band centers can offer in-depth understandings to design efficient bifunctional HER and HzOR electrocatalysts.

Glutathione-mediated copper sulfide nanoplatforms with morphological and vacancy-dependent photothermal catalytic activity for multi-model tannic acid assays

Interface engineering and vacancy engineering play an important role in the surface and electronic structure of nanomaterials. The combination of the two provides a feasible way for the development of efficient photocatalytic materials. Here, we use glutathione (GSH) as a coordination molecule to design a series of CuxS nanomaterials (CuxS-GSH) rich in sulfur vacancies using a simple ultrasonic-assisted method. Interface engineering can induce amorphous structure in the crystal while controlling the formation of porous surfaces of nanomaterials, and the formation of a large number of random orientation bonds further increases the concentration of sulfur vacancies in the crystal structure. This study shows that interface engineering and vacancy engineering can enhance the light absorption ability of CuxS-GSH nanomaterials from the visible to the near-infrared region, improve the efficiency of charge transfer between CuxS groups, and promote the separation and transfer of optoelectronic electron-hole pairs. In addition, a higher specific surface area can produce a large number of active sites, and the synergistic and efficient photothermal conversion efficiency (58.01%) can jointly promote the better photocatalytic performance of CuxS-GSH nanomaterials. Based on the excellent hot carrier generation and photothermal conversion performance of CuxS-GSH under illumination, it exhibits an excellent ability to mediate the production of reactive oxygen species (ROS) through peroxide cleavage and has excellent peroxidase activity. Therefore, CuxS-GSH has been successfully developed as a nanoenzyme platform for detecting tannic acid (TA) content in tea, and convenient and rapid detection of tannic acid is achieved through the construction of a multi-model strategy. This work not only provides a new way to enhance the enzyme-like activity of nanomaterials but also provides a new prospect for the application of interface engineering and vacancy engineering in the field of photochemistry.

Molybdenum/selenium based heterostructure catalyst for efficient hydrogen evolution: Effects of ionic dissolution and repolymerization on catalytic performance

Transition metal chalcogenides (TMCs) are recognized as highly efficient electrocatalysts and have wide applications in the field of hydrogen production by electrolysis of water, but the real catalytic substances and catalytic processes of these catalysts are not clear. The species evolution of Mo and Se during alkaline hydrogen evolution was investigated by constructing MoSe2@CoSe2 heterostructure. The real-time evolution of Mo and Se in MoSe2@CoSe2 was monitored using in situ Raman spectroscopy to determine the origin of the activity. Mo and Se in MoSe2@CoSe2 were dissolved in the form of MoO42- and SeO32-, respectively, and subsequently re-adsorbed and polymerized on the electrode surface to form new species Mo2O72- and SeO42-. Theoretical calculations show that adsorption of Mo2O72- and SeO42- can significantly enhance the HER catalytic activity of Co(OH)2. The addition of additional MoO42- and SeO32- to the electrolyte with Co(OH)2 electrodes both enhances its HER activity and promotes its durability. This study helps to deepen our insight into mechanisms involved in the structural changes of catalyst surfaces and offers a logical basis for revealing the mechanism of the influence of species evolution on catalytic performance.