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In this study, to develop an organic/inorganic synergistic flame retardant and to reduce the dosage and cost of flame retardants, organic/inorganic synergistic flame retardants, hexakis(4-boronic acid-phenoxy)-cyclophosphazene (CP-6B), and magnesium hydroxide (MH) were chosen. The flame retardant properties of CP-6B/MH in epoxy resin (EP) were discussed. EP/CP-6B/MH had better flame retardancy and heat resistance compared with EP/CP-6B and EP/MH. A limiting oxygen index of EP/3.0%CP-6B/0.5%MH of 31.9% was achieved, and vertical burning V-0 rating was achieved. Compared with EP, the cone calorimeter dates of EP/CP-6B/MH decreased. CP-6B/MH inhibited combustion and did little to damage mechanical properties. Besides, the flame retardant mechanism was studied by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and pyrolysis–gas chromatography–mass spectrometry. CP-6B/MH exerted good synergistic effects.

Exploring an efficient and pollution-free hydrogen evolution reaction (HER) electrocatalyst based on the combination of rare-earth metal and nonnoble metal is of significant importance. However, successfully achieving such a goal remains highly challenging. Herein, a nanosheet comprising a MoO2–CeF3 heterojunction (MoO2–CeF3/NF) is successfully prepared via a three-step method. (1) Growth of hexahedral nickel hydroxide [Ni­(OH)2] on a 3D nickel foam (NF) as the scaffold. (2) In situ hydrothermal growth of a precursor nanosheet structure on the scaffold. (3) Calcination treatment at 450 °C in the presence of hydrogen. Herein, the electron redistribution at the heterointerface of CeF3 and MoO2 is a contributing factor toward enhanced HER activity. Appropriate introduction of CeF3 can enlarge the size of nanosheets, increase numerous active sites, increase the catalytic durability of the material, and change electron distribution on the MoO2 interface; all of the above improve HER activity. Because of its interfacial nanosheet structure, MoO2–CeF3/NF demonstrates pre-eminent HER capability in both alkaline (1.0 M KOH) and acidic (0.5 M H2SO4) electrolytes, with extremely small overpotentials of 18 and 42 mV at 10 mA cm–2, respectively. This is obviously lower than the overpotential of Pt/C in alkaline media (27 mV), and it is also close to the overpotential of Pt/C in acidic media (41 mV), at the same current density. More importantly, MoO2–CeF3/NF displays a better HER activity than Pt/C at a current density of >112 mA cm–2 in both alkaline and acidic electrolytes. This work offers a novel strategy toward high-performance hydrogen production by designing a transition metal oxide and rare-earth metal heterojunction.

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