Rational Regulation of Crystalline/Amorphous Microprisms-Nanochannels Based on Molecular Sieve (VSB-5) for Electrochemical Overall Water Splitting

Rational regulation of the composition and structure of electrocatalysts is crucial to the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a new electrocatalyst of nickel phosphate microprism (VSB/NiPO) is developed via a simple solvothermal reaction. The microprism is mainly composed of Versailles-Santa Barbara-5 (VSB-5, molecular sieve) with unique nanochannels, which contribute to accelerating mass transfer and exposing more active sites, thus displaying excellent HER activity. Subsequently, the crystallinity and electronic structure of the framework are modulated by incorporating Fe with the combination of calcination and impregnation. The nanochannels are converted to the amorphous arrangement, and the Ni centers are regulated to the higher valence. The resultant Fe-VSB/NiPO-500 exhibits a low OER overpotential of 227 mV at 50 mA cm^-2 . Interestingly, an integrated electrolyzer assembled by VSB/NiPO(-) and Fe-VSB/NiPO-500(+) performs well for overall water splitting, which requires only 1.487 V to achieve 10 mA cm^-2 , and remains stable at 100 mA cm^-2 over 100 h. This finding opens a new avenue for developing VSB-5 in the field of electrocatalysis.

Nickel phosphate nanorod-enhanced polyethylene oxide-based composite polymer electrolytes for solid-state lithium batteries

Solid-state electrolytes with high ionic conductivity, large electrochemical window, and excellent stability with lithium electrode are needed for high-energy solid-state lithium batteries. In this work, a novel polyethylene oxide (PEO)-Lithium bis(trifluoromethylsulphonyl)imide (LiTFSI)-nanocomposite-based polymer electrolyte was prepared by using nickel phosphate (VSB-5) nanorods as the filler. The ionic conductivity of the obtained PEO-LiTFSI-3%VSB-5 solid polymer electrolyte was found to be as high as 4.83 × 10^-5 S·cm^-1 at 30 °C and electrochemically stable up to about 4.13 V versus Li/Li⁺. The enhanced ionic conductivity was attributed to the reduced crystallinity of the PEO and the interaction between VSB and 5 and PEO-LiTFSI. In addition, the solid polymer electrolyte exhibited improved compatibility to the lithium metal anode with excellent suppression of lithium dendrites. The assembled LiFePO₄/Li battery with the PEO-LiTFSI-3%VSB-5 solid polymer electrolyte showed better rate performance and higher cyclic stability than the PEO-LiTFSI electrolyte. It is demonstrated that this new solid polymer hybrid should be a promising electrolyte applied in solid state batteries with lithium metal electrode.