Scaled-up synthesis of defect-rich layered double hydroxide monolayers without organic species for efficient oxygen evolution reaction

The scaled-up synthesis of organic-free monolayer nanomaterials is highly desirable,especially in obtaining green energy by electrocatalysis.In this study,a method for the scaled-up synthesis of the series of monolayer layered double hydroxides(LDHs)without the addition of organic solvents is reported via the separate nucleation and aging steps process.The resulting monolayer LDHs with the thicknesses of less than 1 nm showed a narrow thickness distribution.X-ray absorption fine-structure revealed that monolayer NiFe-LDH nanosheets have a number of oxygen and metal vacancies defects.As a practical application,monolayer NiFe-LDH nanosheets containing defects showed an enhanced electrocatalytic water oxidation activity compared with that of bulk NiFe-LDH.Density functional theory calculations uncovered that excellent catalytic activity is attributed to vacancies defects.The proposed method is an economical and universally applicable strategy for the scaled-up production of monolayer LDHs.

Freestanding Pt nanosheets with high porosity and improved electrocatalytic performance toward the oxygen reduction reaction

Because of the intriguing electronic properties, high specific surface areas and confinement effect, two-dimensional(2D) noble metal nanosheets usually exhibit fascinating physicochemical properties and thus hold great promises in fuel cell devices and beyond. Herein, 2D porous Pt nanosheets composed by interweaved ultrathin nanowires are successfully fabricated via a facile NaCl-templated process. Controlled experiments demonstrate that the adoption of NaCl and appropriate ratio of NaCl and Pt precursor are indispensable for the formation of porous Pt nanosheets. Impressively, the cost-effective NaCl template can be recyclable through a simple recrystallization procedure, which may greatly reduce the synthetic cost. By virtue of their structural merits, including high porosity, 2D anisotropy and abundant defects, the resultant porous Pt nanosheets exhibit superior activity and enhanced stability towards the oxygen reduction reaction(ORR) compared to the commercial Pt black in alkaline medium. The present study not only offers a high-performance electrocatalyst for fuel cell devices, but also provides a new perspective toward the rational synthesis of 2D noble metal nanosheets with high porosity and diverse functionalities.