Prussian blue analogue assisted formation of iron doped CoNiSe2 nanosheet arrays for efficient oxygen evolution reaction

Core-bishell NiFe@NC@MoS2 for boosting electrocatalytic activity towards ultra-efficient oxygen evolution reaction

Designing and developing suitable oxygen evolution reaction (OER) catalysts with high activity and stability remain challenging in electrolytic water splitting. Hence, NiFe@NC@MoS2 core-bishell composites wrapped by molybdenum disulphide (MoS2) and nitrogen-doped graphene (NC) were prepared using hydrothermal synthesis in this research. NiFe@NC@MoS2 composite exhibits excellent performance with an overpotential of 288 mV and a Tafel slope of 53.2 mV·dec-1 at a current density of 10 mA·cm-2 in 1 M KOH solution, which is superior to commercial RuO2. NC and MoS2 bishells create profuse edge active sites that enhance the adsorption ability of OOH* while lowering the overall overpotential of the product and improving its oxygen precipitation performance. The density function theory(DFT) analysis confirms that the layered MoS2 in NiFe@NC@MoS2 provides additional edge active sites and enhances electron transfer, thus increasing the intrinsic catalytic activity. This research paves a novel way for developing OER electrocatalysts with excellent catalytic performance.

Construction of Bimetallic-Anchored Two-Dimensional Nanosheets on COF for Rechargeable Zinc-Air Batteries

The preparation of carbon materials by doping bimetallic oxides into triazine frameworks (COFs) is a promising electrocatalyst with the potential to replace precious metals in energy storage systems. In this experiment, a covalent triazine framework (COF) was synthesized by 1,4-dicyanobenzene (DCB) and zinc chloride, in which the COF and transition metals were used as carbon, nitrogen, cobalt, and iron sources. According to the properties of this COF, the destruction of the catalyst during pyrolysis can be prevented. The enhanced catalytic performance of the catalysts can be seen by testing all of the samples of catalysts in an alkaline medium. The high half-wave potential (E1/2) of 0.86 V is comparable to Pt/C and also shows excellent durability by testing. Zinc-air batteries were assembled using the prepared catalysts, and the batteries were tested for specific capacity (548 mAh g-1) and power density (189 mW cm-2). This work provides a new direction for COF-derived catalysts for carbon materials.

Zeolitic Imidazolate Framework-Derived Co3S4@NiFe-LDH Core-Shell Heterostructure as Efficient Bifunctional Electrocatalyst for Water Splitting

The development of stable and efficient bifunctional electrocatalysts is of utmost importance for overall water splitting. This study introduces Co3S4@NiFe-LDH core-shell heterostructure prepared via an electrodeposition of ultrathin NiFe-LDH nanosheet on zeolitic imidazolium framework-derived Co3S4 nanosheet arrays. The bifunctional Co3S4@NiFe-LDH/NF exhibits impressive catalytic performance and long-term stability for both the OER and HER with low overpotentials of 100 mA cm-2 at 235 mV and 10 mA cm-2 at 95 mV in 1 M KOH, respectively. The assembled cell with Co3S4@NiFe-LDH/NF as both cathode and anode shows voltages of 1.595 and 1.666 V at current densities of 10 and 20 mA cm-2, respectively, as well as ultralong stability over 500 h. DFT calculations expose a robust electron interaction at the heterogeneous interface of the Co3S4@NiFe-LDH/NF core-shell structure. This interaction promotes electron transfer from NiFe-LDH to Co3S4 and reduces the energy barriers for OER intermediates, thereby enhancing electrocatalytic activity. This research contributes novel insights toward the promising materials for electrochemical water splitting through the construction of heterojunction interfaces.

Discovery of indole analogues from Periplaneta americana extract and their activities on cell proliferation and recovery of ulcerative colitis in mice

Background: As an important medicinal insect, Periplaneta americana (PA) has been applied for the treatment of wounds, burns, and ulcers with fewer side effects and a reduced recurrence rate, which provides great potential for developing new drugs based on its active constituents. Materials and methods: The main chromatographic peaks determined by high performance liquid chromatography (HPLC) in the PA concentrated ethanol-extract liquid (PACEL) were separated, purified, and identified by semi-preparative LC, mass spectrum, and 1H NMR spectroscopic analysis. The biological activities of the identified compounds were investigated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) method based on in vitro human skin fibroblasts (HSF) and in vivo experiments based on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) mouse model. Furthermore, RT-qPCR of six genes related to inflammation or intestinal epithelial cell proliferation was employed to investigate the molecular mechanism of the indole analogues recovering UC in mice. Results: Five indole analogues were purified and identified from PACEL, including tryptophan (Trp), tryptamine (pa01), 1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa02), (1S, 3S)-1-methyl-1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa03), and (1R, 3S)-1-methyl-1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa04), among which the pa02 and pa04 were reported in PA for the first time. In vitro and in vivo experiments showed that PACEL, Trp, and pa02 had promoting HSF proliferation activity and intragastric administration of them could alleviate symptoms of weight loss and colon length shortening in the UC mice. Although recovery activity of the compound pa01 on the colon length was not as obvious as other compounds, it showed anti-inflammatory activity in histological analysis. In addition, The RT-qPCR results indicated that the three indole analogues could alleviate DSS-induced intestinal inflammation in mice by inhibiting pro-inflammatory cytokines (MMP7, IL1α) and down-regulating BMP8B expression. Conclusion: This study reported the isolation, purification, structure identification, and biological activity of the active indole analogues in PACEL. It was found for the first time that the PA extract contained many indole analogues and Trp, which exhibited good proliferation activity on HSF fibroblasts as well as anti-UC activity in mice. These indole analogues probably are important components related to the pharmacological activity in PA.

Unveiling the Structural Self-Reconstruction and Identifying the Reactive Center of a V, Fe Co-Doped Cobalt Precatalyst toward Enhanced Overall Water Splitting by Operando Raman Spectroscopy

The development of efficient and stable bifunctional electrocatalysts based on non-noble metals for water electrolysis is both urgent and challenging. However, unresolved issues remain regarding the challenge of identifying the active phase and gaining a comprehensive understanding of its surface reconstruction and functionality throughout the reaction process. In this study, we have combined doping and heterostructure construction by a one-step electrodeposition and a subsequent activation treatment to synthesize Fe, V co-doped Co3O4/Co(OH)2 and Co/Co(OH)2 heterointerfaces (referred to as A-Co60Fe1.1V). These heterointerfaces, composed of Co/Co(OH)2 and Co3O4/Co(OH)2, are proposed to facilitate charge transfer process during catalysis. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the introduction of V and Fe dopants increases the valence state of Co centers in Co3O4 and Co(OH)2. Further operando Raman spectroscopy reveals that Co(OH)2 and Co3O4 with the high-valence Co centers remain stable during the hydrogen evolution reaction (HER) process. These high-valence Co centers are believed to promote the crucial water dissociation step and therefore enhance the overall HER catalysis. On the other hand, during the oxygen evolution reaction (OER), Fe, V co-doping leads to an earlier formation of the active CoOOH species, while Fe doping can further help stabilize the more reactive β-CoOOH species instead of the less reactive γ-CoOOH. As a result, the A-Co60Fe1.1V catalyst exhibits significantly improved catalytic activity for both HER and OER that it requires low overpotentials of 51 and 250 mV, respectively, to attain a current density of 10 mA cm-2. Moreover, when utilized as both the cathode and anode in alkaline water electrolysis, the A-Co60Fe1.1V catalyst can operate at a mere 1.54 V voltage while maintaining 10 mA cm-2, surpassing the majority of non-noble metal catalysts. Remarkably, it also exhibits stability for at least 40 h at ∼100 mA cm-2.

3D nanostructured Ce-doped CoFe-LDH/NF self-supported catalyst for high-performance OER

Powder electrocatalysts for oxygen evolution reactions usually need adhesives for electrocatalytic performance tests, leading to the increase of resistance, reduction of catalyst loading, and easy stripping of the catalyst under long-time or high current operation. In this study, Ce-doped CoFe layered double hydroxides were uniformly grown on nickel foam by a one-step hydrothermal route. A nanostructured self-supported electrode Ce-CoFe-LDH/NF without adhesive was obtained directly, which has a regular nanoneedle morphology with a length of ∼1.2 μm and tip width of ∼20 nm. Adopting Ce3+ ions with a large radius to partially displace Fe3+ ions with a small radius produced lattice distortion and more defects in the host layer of CoFe-LDH, whereby possessing the great potential to enhance catalytic behaviors. Once used as an electrocatalyst for the oxygen evolution reaction, Ce-CoFe-LDH/NF shows an outstanding electrocatalytic performance, including an optimized overpotential of 225 mV at 10 mA cm-2, a decreased Tafel slope of 34.34 mV dec-1, and a low charge transfer impedance of 2.4 Ω in 1 M KOH electrolyte. Moreover, the overpotential of the working electrode increased by only 0.04 V after 24 hours and was maintained at a current density of 50 mA cm-2. These results demonstrate a low-cost strategy compared to using noble metal OER electrocatalysts. Thus, this study highlights a ready universal approach to fabricate high-performance supported catalysts for energy-related applications.

Iron-modulated Ni3S2 derived from a Ni-MOF-based Prussian blue analogue for a highly efficient oxygen evolution reaction

Developing efficient, environmentally friendly and cost-effective non-precious metal electrocatalysts for the oxygen evolution reaction (OER) is essential to alleviate the energy crisis and environmental pollution.