Sulphur and nitrogen dual-doped mesoporous carbon hybrid coupling with graphite coated cobalt and cobalt sulfide nanoparticles: Rational synthesis and advanced multifunctional electrochemical properties

Boosting oxygen reduction durability by embedding Co9S8 nanoparticles into Co single atoms anchored porous carbon frameworks

Developing an efficient and low-cost oxygen reduction electrocatalyst is essential for the application of aqueous zinc-air batteries (ZABs). Herein, we report a facile adsorption-confined pyrolysis strategy to fabricate the hybrid electrocatalyst (denoted as Co9S8/CoSA-PC) by embedding Co9S8 nanoparticles into Co single atoms (Co-SAs) anchored porous carbon sheets for boosting oxygen reduction reaction (ORR) durability. In this strategy, the Co2+ ions are first absorbed into oxygen-rich porous carbon nanosheets and further form the Co-SAs with the help of thiourea in the following pyrolysis procedure, which is believed to be able to confine the generated Co9S8 nanoparticles into carbon frameworks due to their interface interaction. Benefiting from the synergistic effect of different components, the obtained Co9S8/CoSA-PC electrocatalyst for ORR exhibits outstanding catalytic activity with a half-wave potential of 0.82 V and a distinguished long-term durability with a current retention of 80 % after cycling 80 h under alkaline conditions, which is superior to commercial Pt/C. Moreover, the assembled ZABs with Co9S8/CoSA-PC as cathodic catalyst deliver a high specific capacity of 764 mAh gZn-1 at 10 mA cm-2 and the outstanding peak power density of up to 221.4 mW cm-2. This work provides a novel structure design strategy to prepare transition metal sulfide-based electrocatalysts with superior durability for ORR.

Synthesis of multi-cavity mesoporous carbon nanospheres through solvent-induced self-assembly: Anode material for sodium-ion batteries with long-term cycle stability

Mesoporous carbon nanospheres (MCSs) are extensively employed in energy storage applications due to their ordered pore size, large specific surface area (SSA), and abundant active sites, resulting in excellent electrochemical performance for sodium storage. However, challenges persist in achieving precise structural control and stable synthesis reactions for these MCSs. Additionally, employing MCSs with a larger SSA in sodium storage applications can lead to increased side reactions and potential structural instability. To address these issues, we propose a solvent-induced self-assembly method for obtaining high nitrogen-containing multi-cavity MCSs with reduced SSA. The morphology and SSA of the nanospheres can be precisely adjusted by regulating the reaction time. Introducing an amine-phenol bridging structure into the polymer system significantly bolsters the structural and morphological stability of the mesoporous materials. The performance of these novel nanospheres in sodium-ion batteries (SIBs) is remarkable, exhibiting excellent sodium storage capability and exceptional ultra-long cycle stability. At a rate of 0.1 A g-1, the nanospheres achieved a high reversible capacity of 252 mAh g-1, and even after 20,000 cycles at 5 A g-1, a specific capacity of 136 mAh g-1 was retained. In summary, our study presents a novel approach for synthesizing mesoporous carbon materials and offers valuable insights for sodium storage research, opening new possibilities for enhancing energy storage applications.

Rational design of the Z-scheme hollow-structure Co9S8/g-C3N4 as an efficient visible-light photocatalyst for tetracycline degradation

The development of photocatalysts with high catalytic activity that are capable of full utilization of solar energy is a challenge in the field of photocatalysis. Accordingly, in the present study, an efficient Z-scheme cage-structured Co₉S₈/g-C₃N₄ (c-CSCN) photocatalyst was constructed for the degradation of tetracycline antibiotics under visible-light irradiation. The Z-scheme charge-transfer mechanism accelerates the separation of photogenerated charge carriers and effectively improves photocatalytic activity. Moreover, c-CSCN has a hollow structure, allowing light to be reflected multiple times inside the cavity, thereby effectively improving the utilisation efficiency of solar energy. As a result, the photocatalytic activity of c-CSCN is 1.5-, 2.5-, and 5.8-times higher than those of sheet-type Co₉S₈/g-C₃N₄ (s-CSCN), c-Co₉S₈, and g-C₃N₄, respectively, for the degradation of tetracycline. c-CSCN maintains favourable photocatalytic activity over five consecutive degradation cycles, demonstrating its excellent stability. In addition, c-CSCN performs efficient tetracycline removal in different water substrates. Moreover, c-CSCN exhibits excellent ability to remove tetracycline under direct natural sunlight. This work fully demonstrates that c-CSCN has high catalytic activity and the potential for practical application as a wastewater treatment material.

Fabrication of Hierarchical Co9S8@ZnAgInS Heterostructured Cages for Highly Efficient Photocatalytic Hydrogen Generation and Pollutants Degradation

In the present study, a hierarchical Co₉S₈@ZnAgInS heterostructural cage was developed for the first time which can photocatalytically produce hydrogen and degrade organic pollutants with high efficiency. First, the Co₉S₈ dodecahedron was synthesized using a metal-organic framework (MOFs) material, ZIF-67, as a precursor, then two kinds of metal sulfide semiconductors were elaborately integrated into a hierarchical hollow heterostructural cage with coupled heterogeneous shells and 2D nanosheet subunits. The artfully designed hollow heterostructural composite exhibited remarkable photocatalytic activity without using any cocatalysts, with a 9395.3 μmol g^-1 h^-1 H₂ evolution rate and high degradation efficiency for RhB. The significantly enhanced photocatalytic activity can be attributed to the unique architecture and intimate-contact interface between Co₉S₈ and ZnAgInS, which promote the transfer and separation of the photogenerated charges, increase light absorption, and offer large surface area and active sites. This work presents a new strategy to design highly active semiconductor photocatalysts by using MOF materials as precursors and coupling of metal sulfide semiconductors to form hollow architecture dodecahedron cages with an intimate interface.

Sodium borohydride-assisted synthesis of strontium substituted lanthanum cobaltate with in-situ generated cobaltosic oxide: Towards enhanced oxygen evolution reaction in alkaline media

Based on the intrinsic behaviour of doped Co-based perovskite to generate the second phase of Co₃O₄, a novel strategy was developed to synthesize a hybrid catalyst consisting of La_1-xSr_xCoO_3-δ (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) and in-situ generated Co₃O₄ in the presence of NaBH₄. When x increased to 1.0, a well-designed integration (SrCoO_2.5@Co₃O₄) was obtained which displayed the optimal OER activity with an overpotential of 330 mV at 10 mA cm^-2, a small Tafel slope of 66.7 mV dec^-1 and terrific durability in alkaline media. This excellent performance can be attributed to the auxiliary of the in-situ generated Co₃O₄ for SrCoO_2.5 which modifies the chemical states of Co cations, compensates for the unsatisfactory electrical conductivity of SrCoO_2.5 while preserves oxygen vacancies, boosts the content of lattice oxygen and exposes more active sites. This work is expected to provide a new mind to design effective electrocatalysts towards water splitting.

Efficient Oxygen Electrocatalyst for Zn-Air Batteries: Carbon Dots and Co9S8 Nanoparticles in a N,S-Codoped Carbon Matrix

Non-noble metal-based bifunctional electrocatalysts for both oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) are an essential component of high-performance rechargeable Zn-air batteries (ZABs). Herein, we report a novel and simple method for preparing Co₉S₈ nanoparticles embedded in N and S codoped carbon materials with aid of carbon dots (CDs). CDs play a key role in distributing Co₉S₈ nanoparticles in the matrix uniformly and enhancing the specific surface area and the electric conductivity simultaneously. The obtained Co₉S₈/CD@NSC exhibits an excellent ORR and OER bifunctional catalytic activity and a great long-term durability, with a half-wave potential of 0.84 V versus reversible hydrogen electrode (RHE) for the ORR and a low potential of 1.62 V versus RHE at 10 mA cm^-2, which outperform the popular Pt/C and RuO₂ commercial catalysts. Moreover, the Co₉S₈/CD@NSC catalyst also displays a superior activity and cycling stability as a cathode material in ZABs, which is far better than Pt/C + RuO₂ mixture catalysts. Such a ZAB shows a low charge/discharge voltage gap of 0.62 V and great cycling stability over 125 h at 10 mA cm^-2.

Recent Advances of Cobalt-Based Electrocatalysts for Oxygen Electrode Reactions and Hydrogen Evolution Reaction

This review summarizes recent progress in the development of cobalt-based catalytic centers as the most potentially useful alternatives to noble metal-based electrocatalysts (Pt-, Ir-, and Ru-based) towards the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in acid and alkaline media. A series of cobalt-based high-performance electrocatalysts have been designed and synthesized including cobalt oxides/chalcogenides, Co–Nx/C, Co-layered double hydroxides (LDH), and Co–metal-organic frameworks (MOFs). The strategies of controllable synthesis, the structural properties, ligand effect, defects, oxygen vacancies, and support materials are thoroughly discussed as a function of the electrocatalytic performance of cobalt-based electrocatalysts. Finally, prospects for the design of novel, efficient cobalt-based materials, for large-scale application and opportunities, are encouraged.

Copper–nickel embedded into a nitrogen-doped carbon octahedron as an effective bifunctional electrocatalyst

The CuNi-NC serves as an efficient bifunctional catalyst for HER and OER, in which the role of Ni is investigated in detail.

Novel two-dimensional Bi4V2O11 nanosheets: controllable synthesis, characterization and insight into the band structure

Novel two-dimensional Bi₄V₂O₁₁ nanosheets were controllably prepared using a stable [Bi(EDTA)]⁻ complex, and their band structures were investigated as well.

C–S bond induced ultrafine SnS2 dot/porous g-C3N4 sheet 0D/2D heterojunction: synthesis and photocatalytic mechanism investigation

A C–S bond induced novel ultrafine SnS₂ dot/porous g-C₃N₄ sheet 0D/2D heterojunction for enhanced carrier separation and photocatalytic activities was developed.