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

Abstract

A high-entropy oxide nanocomposite with Ag(CuZn)(AlCr)2O4 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)2O4 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–1 h–1 of H2 without external light irradiation, which is 980% higher than the H2 produced by the same nanocomposite under the photocatalytic process. A strong electrical field is observed at the interface between the Ag(CuZn)(AlCr)2O4 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.

An ultraefficient surface functionalized Ti3C2Tx MXene piezocatalyst: synchronous hydrogen evolution and wastewater treatment

“…Researchers have developed new material systems with noncentrosymmetric structures using various piezoelectric and ferroelectric materials, including ZnSnO 3 , 21 BaTiO 3 , 22,23 BiFeO 3 , 24 MoSe 2 , 25 WS 2 , 26 and ferroelectric high entropy oxides. 27,28 These materials and heterostructures 29 are currently being explored for use in piezocatalysis. 30,31…”

“…Researchers have developed new material systems with noncentrosymmetric structures using various piezoelectric and ferroelectric materials, including ZnSnO 3 , 21 BaTiO 3 , 22,23 BiFeO 3 , 24 MoSe 2 , 25 WS 2 , 26 and ferroelectric high entropy oxides. 27,28 These materials and heterostructures 29 are currently being explored for use in piezocatalysis. 30,31 Similar to 2D transition metal dichalcogenides (TMDs), MXenes [32][33][34][35][36] are a recently discovered family of 2D transition metal carbides/nitrides, M n+1 X n T x , that have been transformed from the MAX phase.…”