Parallel Regulation of Charge Dynamics on Bipolar Ferroelectric Surfaces Breaks the Limits for Water Splitting Efficiency

Abstract

Ferroelectric materials, known for their non-inversion symmetry, show promise as photocatalysts due to their unique asymmetric charge separation, which separates hydrogen and oxygen evolution sites. However, the strong depolarized field induces a relaxed surface structure, which in turn directly leads to slow hole charge transfer dynamics, hindering their efficiency in water splitting. In this study, a fundamental breakthrough in dramatically enhancing the overall water-splitting activity is presented, through the synergistically regulating of the surface behaviors of photogenerated carriers, resulting in nearly perfect parallel dynamics and balanced amounts. By depositing atomic layers of TiO₂ onto the surface of PbTiO₃, surface vacancies are effectively passivated, significantly prolonging the hole lifetime from 10⁻⁶ to 10⁻³ s. Spatially resolved transient photovoltage spectroscopy showed that improved hole dynamics led to a 180° phase shift between photogenerated electrons and holes, indicating nearly identical extraction dynamics. Notably, hole and electron concentrations increased to equivalent levels. This leads to a nearly 578-fold increment in the apparent quantum yield, resulting in significantly increased overall water-splitting rates, with a quantum yield of 5.78% at 365 nm. The strategy is also effective with Al₂O₃ and SiO₂, demonstrating its versatility across varied materials, providing a valuable method for creating high-performance ferroelectric photocatalysts.