Flexoelectric Catalysts Based on Hierarchical Wrinkling Surface of Centrosymmetric High-Entropy Oxide.

Wu, Ping Yun; Le, Kim Tuyen; Lin, Hsun-Yen; Chen, Yu-Ching; Wu, Po-Han; Wu, Jyh Ming · ACS Nano · 2023

basic_science · Level V

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Abstract

A high-entropy oxide nanocomposite with Ag(CuZn)(AlCr)<sub>2</sub>O<sub>4</sub> and CuO phases is fabricated to form an abundantly hierarchical wrinkled surface. Application of a mechanical force to the nanocomposite resulted in a nonhomogeneous strain gradient at the interface between the Ag(CuZn)(AlCr)<sub>2</sub>O<sub>4</sub> and CuO phases, changing the local charge distribution and creating flexoelectric polarization that delayed electron/hole recombination. Transmission electron microscopy energy-dispersive X-ray spectroscopy mapping revealed that the Ag, Cu, Zn, Al, Cr, and O elements were highly distributed throughout the nanocomposite. The nanocomposite produced 2116 μmol·g<sup>-1</sup> h<sup>-1</sup> of H<sub>2</sub> without external light irradiation, which is 980% higher than the H<sub>2</sub> produced by the same nanocomposite under the photocatalytic process. A strong electrical field is observed at the interface between the Ag(CuZn)(AlCr)<sub>2</sub>O<sub>4</sub> and CuO phases, demonstrating that a flexoelectric potential (flexopotential) is established at the structural boundaries because the strain gradient is localized at these interfaces. The nanocomposite is a promising approach for environmentally friendly energy production.