Polarization Rearrangement Induced High-Efficiency Piezocatalytic Overall Pure Water Splitting in Ultrathin (001)-Confined PbTiO3

Abstract

Facing the emergencies of global warming and energy shortages, nano ferroelectrics, which exhibit superior charge separation capabilities and polarization tunability, are extensively utilized in piezocatalytic H₂ production. However, acquiring polarized structures that behave with robust ferroelectricity and strong piezoelectricity in ultralow dimension nanomaterials for efficient piezocatalysis remains a huge challenge. This research achieved exceptional piezocatalytic overall pure water splitting performance in 3.5 nm-thick (001)-confined PbTiO₃ nanosheets, reaching a H₂ evolution rate of 1068 μmol g^–1 h^–1, exceeding those of similar ferroelectric oxides. The highly confined crystallographic polarization orientation in nanosheets induced polarization rearrangement from the c-axis to other nonpolarized crystallographic orientations, as evidenced by piezoelectric force microscopy and phase field simulations, which improve piezoelectricity and boost piezocatalytic behavior significantly. Local structure investigations jointly by neutron pair distribution function, X-ray absorption spectrum, and atomic-scale scanning transmission electron microscopy methods show that the rearranged structure arises from the lattice inhomogeneous tensile strain. TiO₆ octahedrons were distorted, with the Ti atom moving diagonally toward the symmetry center. Such ferroelectric reconstruction of a practical nanopolarized structure with remarkable performance in this work will promote the development of high-performance nano ferroelectrics.