Piezo-photocatalysts based on a ferroelectric high-entropy oxide

We develop a porous ferroelectric high-entropy oxide (HEO) by tuning the Ca concentration in (CaxZrYCeCr)O2 (x = 0.09-0.5). Time-resolved photoluminescence indicates that the ferroelectric HEO sample containing 38 at% Ca atoms (38HEO) exhibits a long carrier lifetime of approximately 66 ns, 163% of the lifetime of Zr0.3Y0.3-Ce0.3Cr0.09O2. The theoretical calculation reveals that the porous HEO into which ferroelectric Ca(Zr0.95Cr0.5)O3 nanoparticles are embedded, separating electron-hole pairs efficiently and provides trapping centers in the piezocatalytic process, considerably prolonging the carrier lifetime. The reaction rate constant of 38HEO for the decomposition of dye molecules is 1000% of that for pristine ZrYCeCrO2. The hydrogen evolution reaction with polarized 38HEO resulted in hydrogen production of 677 mu molg_ 1h_ 1, 163% that of unpolarized 38HEO. The piezopotential of the ferroelectric Ca(Zr1_xCrx)O3 was strongly coupled with the charge transfer of the HEO's surface, enhancing the catalytic activity. The concepts reported herein can be used to design next-generation piezo-photocatalysts.