Role of piezo-, ferro-electric and built-in electric fields in regulating the performance of photocatalysts

Photo(electro)catalytic technologies employ renewable solar energy to address the energy crisis and mitigate environmental pollution. However, solar-energy-based applications suffer from limitations owing to low conversion efficiencies, mainly because the driving force for charge separation and transfer within photoelectrode materials is insufficient. Herein, we review the formation mechanisms of polarized electric fields in piezoelectric and ferroelectric photo(electro)catalytic materials, describe the photocatalytic properties of these materials, and discuss recent research progress. Moreover, the application of defect engineering to construct internally polarized electric fields is discussed. Constructing polarization internal fields via defect engineering is an effective method for driving charge separation and transfer in photoelectrode materials without intrinsic polarized electric fields. Reversible dipoles can be constructed by introducing defect dipoles and developing adjustable ferroelectric-like fields through the synergistic regulation of domain and grain boundaries. The mechanism of polarization in bulk materials is complicated, and controlling the induction and regulation of piezoelectric internal polarized electric fields is difficult. We aim to identify the key factors of constructed internal fields involved in the regulation of photo(electro)catalytic performance, clarify the structure-activity relationships between internal electric fields and photo(electro)catalytic characteristics, and guide the design and preparation of highly active photo(electro)catalytic materials.