NiCo2S4 spheres grown on N,S co-doped rGO with high sulfur vacancies as superior oxygen bifunctional electrocatalysts

Unveiling the Role of Sulfur Vacancies in Enhanced Photocatalytic Activity of Hybrids Photocatalysts

Photocatalysis represents a sustainable strategy for addressing energy shortages and global warming. The main challenges in the photocatalytic process include limited light absorption, rapid recombination of photo-induced carriers, and poor surface catalytic activity for reactant molecules. Defect engineering in photocatalysts has been proven to be an efficient approach for improving solar-to-chemical energy conversion. Sulfur vacancies can adjust the electron structure, act as electron reservoirs, and provide abundant adsorption and activate sites, leading to enhanced photocatalytic activity. In this work, we aim to elucidate the role of sulfur vacancies in photocatalytic reactions and provide valuable insights for engineering high-efficiency photocatalysts with abundant sulfur vacancies in the future. First, we delve into the fundamental understanding of photocatalysis. Subsequently, various strategies for fabricating sulfur vacancies in photocatalysts are summarized, along with the corresponding characterization techniques. More importantly, the enhanced photocatalytic mechanism, focusing on three key factors, including electron structure, charge transfer, and the surface catalytic reaction, is discussed in detail. Finally, the future opportunities and challenges in sulfur vacancy engineering for photocatalysis are identified.

Electrospinning-derived transition metal/carbon nanofiber composites as electrocatalysts for Zn-air batteries

The sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) significantly impede the broader implementation of Zn-air batteries (ZABs), underscoring the necessity for advanced high-efficiency materials to catalyze these electrochemical processes. Recent advancements have highlighted the potential of transition metal/carbon nanofiber (TM/CNF) composite materials, synthesized via electrospinning technology, due to their expansive surface area, profusion of active sites, and elevated catalytic efficacy. This review comprehensively examines the structural characteristics of TM/CNFs, with a particular emphasis on the pivotal role of electrospinning technology in fabricating diverse structural configurations. Additionally, it delves into the mechanistic underpinnings of various strategies aimed at augmenting the catalytic activity of TM/CNFs. A meticulous discourse is also presented on the application scope of TM/CNFs in the realm of electrocatalysis, with a special focus on their impact on the performance of assembled ZABs. Lastly, this review encapsulates the challenges and future prospects in the development of TM/CNF composite materials via electrospinning, aiming to provide an exhaustive understanding of the current state of research in this domain and to foster further advancements in the commercialization of ZABs.

Hollow N-doped carbon nano-mushroom encapsulated hybrid Ni3S2/Fe5Ni4S8 particle anchored to the inner wall of porous wood carbon for efficient oxygen evolution electrocatalysis

Structural design and morphology engineering are considered significant strategies to boost the catalytic performance of electrocatalysts toward the oxygen evolution reaction. Inspired by the natural porosity and abundant functional groups, herein, hollow N-doped carbon nano-mushroom (NCNM) encapsulated hybrid sulfide particles rooted into a carbonized wood (CW) framework were prepared through simple impregnation followed by calcination. The as-prepared self-supporting electrodes present ultrahigh activity and robust stability. Among them, the NiFeS14@NCNM/CW catalyst yields incredible OER activity with an extraordinarily low overpotential of 147 and 250 mV to reach 10 and 50 mA cm-2, respectively, superior to most of the state-of-the-art wood-derived electrocatalysts. Additionally, a steady OER current density is maintained without obvious attenuation after continuous operation for 24 h. The superior electrocatalytic performance of NiFeS14@NCNM/CW is attributed to the synergistic effect of hybridization between Ni3S2 and Fe5Ni4S8, the coordination of one-dimensional (1D) NCNMs and hierarchical three-dimensional (3D) porous CW, modified electronic states by N and S doping, a large electrochemical surface area, and low activation energy. This research provides a novel approach to industrial-scale conversion of abundant biomass into efficient binder-free electrocatalysts for energy-related applications.

Interfacial Electron Redistribution of FeCo2S4/N-S-rGO Boosting Bifunctional Oxygen Electrocatalysis Performance

Developing bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for the development of zinc–air batteries (ZABs), but several challenges remain in terms of bifunctional activity. FeCo2S4/N-S-rGO was prepared by in situ homogeneous growth of bimetallic sulfide FeCo2S4 on N, S-doped reduced graphene oxide. FeCo2S4/N-S-rGO exhibits a half-wave potential of 0.89 V for ORR and an overpotential of 0.26 V at 10 mA cm−2 for OER, showing significantly bifunctional activity superior to Pt/C (0.85 V) and RuO2 (0.41 V). Moreover, the FeCo2S4/N-S-rGO assembled ZAB shows a superior specific capacity and a power density of 259.13 mW cm−2. It is demonstrated that the interfacial electron redistribution between FeCo2S4 nanoparticles and heteroatom-doped rGO matrix can efficiently improve the electrochemical performance of the catalyst. The results provide new insights into the preparation of high-capability composite catalysts combining transition metal sulfides with carbon materials for applications in ZABs.

Interaction between Nickel Oxide and Support Promotes Selective Catalytic Reduction of NOx with C3H6

Selective catalytic reduction of NO x by C 3 H 6 (C 3 H 6 -SCR) was investigated over NiO catalysts supported on different metaloxides. A NiAlO x mixed oxide phase was formed over NiO/γ-Al 2 O 3 catalyst, inducing an immediate interaction between NiO x and AlO x species. Such interaction resulted in a charge transfer from Ni to Al site and the formation of Ni species in high oxidation state. In comparison to other NiO-loaded catalysts, NiO/γ-Al 2 O 3 catalyst exhibited the highest NO x conversion at temperature higher than 450 °C, but a poor C 3 H 6 oxidation activity due to the decreased nucleophilicity for surface oxygen species. By temperatureprogramed NO oxidation, it is indicated that nitrate species were rapidly formed and stably maintained at high temperature over NiO/γ-Al 2 O 3 catalyst. In situ transient reactions further verified the LangmuirHinshelwood mechanism for C 3 H 6 -SCR, where both gaseous NO and C 3 H 6 were adsorbed and activated on catalyst surface and reacted to generate N 2 . Due to the strong metal-support interaction over NiO/γ-Al 2 O 3 catalyst, both nitrate and C x H y O z intermediates were well preserved to attain high C 3 H 6 -SCR activity.

ZnS modified N, S dual-doped interconnected porous carbon derived from dye sludge waste as high-efficient ORR/OER catalyst for rechargeable zinc-air battery

Facile and rational design of high-efficient oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional electrocatalysts is significant for rechargeable Zinc-air batteries. In this study, ZnS modified N, S dual-doped interconnected porous carbon (ZnS/NSC) derived from the dye sludge waste is successfully fabricated via a facile ZnCl₂-assisted pyrolysis process. The effect of ZnCl₂ and carbonization temperature on the microstructure and electrocatalytic performance is systematically investigated. By virtue of the synergistic effect between ZnS nanoparticles and N, S dual-doped porous carbon network, the obtained catalyst ZnS/NSC calcined at 1000 °C exhibits a decent bifunctional electrocatalytic performance with potential gap (ΔE=E_OER,10-E_ORR,1/2) of 0.76 V comparable with commercial electrocatalysts (Pt/C and RuO₂). In addition, a rechargeable zinc-air battery employed ZnS/NSC-1000 as the air cathode also displays the favorable electrochemical performance, in which the power density is 125 mW cm^-2, the specific capacity is 763.27 mAh g^-1 and the cycling stability at 10 mA cm^-2 is more than 85 h, indicating a promising application prospect in rechargeable Zinc-air batteries.

1T-Phase molybdenum sulfide/cobalt oxide nanopillars hybrid nanostructure coupled with nitrogen-doped carbon thin-film as high efficiency electrocatalyst for oxygen evolution

High efficient and durable catalysts are always needed to lower the kinetic barriers as well as prolong the service life associated with oxygen evolution reaction (OER). Herein, a sequential synthetic strategy is considered to prepare a hierarchical nanostructure, in which each component can be configured to achieve their full potential so that endows the resulting nanocatalyst a good overall performance. In order to realize this, well-organized cobalt oxide (Co₃O₄) nanopillars are firstly grown onto ultrathin 1T-molybdenum sulfide (1T-MoS₂) to obtain high surface area electrocatalyst, providing electron transfer pathways and structural stability. After that, zeolitic imidazolate framework-67 (ZIF-67) derived carbonization film is further in situ deposited on the surface of nanopillars to generate plentiful active sites, thereby accelerating OER kinetics. Based on the combination of different components, the electron transfer capability, catalytic activity and durability are optimized and fully implemented. The obtained nanocatalyst (defined as 1T-MoS₂/Co₃O₄/CN) exhibits the superior OER catalytic ability with the overpotential of 202 mV and Tafel slope of 57 mV·dec^-1 at 10 mA·cm^-2 in 0.1 M KOH, and good durability with a minor chronoamperometric decay of 9.15 % after 60,000 s of polarization.

Structural Modulation on NiCo2 S4 Nanoarray by N Doping to Enhance 2e-ORR Selectivity for Photothermal AOPs and Zn-O2 Batteries*

As a H₂ O₂ generator, a 2e^- oxygen reduction reaction active electrocatalyst plays an important role in the advanced oxidation process to degrade organic pollutants in sewage. To enhance the tendency of NiCo₂ S₄ towards the 2e^- reduction reaction, N atoms are doped in its structure and replace S^2- . The result implies that this weakens the interaction between NiCo₂ S₄ and OOH*, suppresses O-O bond breaking and enhances H₂ O₂ selectivity. This electrocatalyst also shows photothermal effect. Under photothermal heating, H₂ O₂ produced by the oxidation reduction reaction can decompose and releaseOH, which degrades organic pollutants through the advanced oxidation process. Photothermal effect induced by the advance oxidation process shows obvious advantages over the traditional Fenton reaction, such as wide pH adaptation scope and low secondary pollutant due to its Fe²⁺ free character. With Zn as anode and the electrocatalyst as cathode material, a Zn-O₂ battery is assembled. It achieves electricity generation and photothermal effect induced by the advance oxidation process simultaneously.

Optimal control of the compositions, interfaces, and defects of hollow sulfide for electromagnetic wave absorption

The aimlessness in the selection of dielectric absorbing materials and the regulation of complex permittivity consumes time and resources. It is an effective way to construct electromagnetic wave (EMW)-absorbing materials dominated by dielectric loss to select materials and adjust complex permittivity based on theory. With sulfide as an example, a hollow ZnO/ZnS composite was constructed using ZnO as a hard template. Subsequently, based on the diverse binding ability of Cu and Zn ions to S ions, the compositions, interfaces, and defects of the sample were simultaneously regulated. There was competition and synergy between the relaxation process caused by the defects and interfaces and the conductivity loss, resulting in the regulation of complex permittivity. Furthermore, the hollow structure effectively reduced the density of the material and improved the impedance matching ability of the sample. As a result, the effective absorption bandwidth (EAB) of the hollow nanoflower ZnO/ZnS/CuS composite reached 5.2 GHz (from 12.8 to 18 GHz) with a matching thickness of 1.59 mm. This method provides a direction for ameliorating the complex permittivity of EMW-absorbing materials dominated by dielectric loss to realize broadband absorption.

Sulfur Vacancy-Rich O-Doped 1T-MoS2 Nanosheets for Exceptional Photocatalytic Nitrogen Fixation over CdS

Here, we reported that sulfur vacancy-rich O-doped 1T-MoS₂ nanosheets (denoted as SV-1T-MoS₂) can surpass the activity of Pt as cocatalysts to assist in the photocatalytic nitrogen fixation of CdS nanorods. SV-1T-MoS₂ cocatalysts exhibit sulfur vacancies, O-doping, more metallic 1T phase, and high electronic conductivity, thus leading to the exposure of more active edge sites, high Brunauer-Emmett-Teller surface area, enhanced visible light absorption, and improved electron separation and transfer, which are beneficial for photocatalytic nitrogen fixation. Consequently, the optimized 30 wt % SV-1T-MoS₂-/CdS composites exhibit an outstanding nitrogen fixation rate of 8220.83 μmol L^-1 h^-1 g^-1 and long-term stability under simulated solar light irradiation, significantly higher than pure CdS nanorods, CdS-Pt (0.1 wt %), and 30 wt % 1T-MoS₂/CdS composites. The catalytic mechanism of photocatalytic nitrogen fixation on SV-1T-MoS₂ is discussed by density functional theory calculations.