The Role of Polarization in Photocatalysis

Abstract

Semiconductor photocatalysis as a desirable technology shows great potential in environmental remediation and renewable energy generation, but its efficiency is severely restricted by the rapid recombination of charge carriers in the bulk phase and on the surface of photocatalysts. Polarization has emerged as one of the most effective strategies for addressing the above‐mentioned issues, thus effectively promoting photocatalysis. This review summarizes the recent advances on improvements of photocatalytic activity by polarization‐promoted bulk and surface charge separation. Highlighted is the recent progress in charge separation advanced by different types of polarization, such as macroscopic polarization, piezoelectric polarization, ferroelectric polarization, and surface polarization, and the related mechanisms. Finally, the strategies and challenges for polarization enhancement to further enhance charge separation and photocatalysis are discussed.

Coupling Piezocatalysis and Photocatalysis in Bi4NbO8X (X = Cl, Br) Polar Single Crystals

“…As shown in Figure a,b, the absorption edges of Bi 4 NbO 8 Cl and Bi 4 NbO 8 Br are located at around 510 nm, demonstrating relatively strong absorption in visible light region for both samples. The bandgap of Bi 4 NbO 8 Cl and Bi 4 NbO 8 Br is determined to be ≈2.48 eV by the Kubelka–Munk (KM) equation . Mott–Schottky plots show that the conduction band (CB) positions of Bi 4 NbO 8 Cl and Bi 4 NbO 8 Br are ≈−1.14 and −0.88 eV versus normal hydrogen electrode, respectively (Figure c).…”

Modulating Charge Separation Efficiency of Water Oxidation Photoanodes with Polyelectrolyte‐Assembled Interfacial Dipole Layers

“…In this study, we demonstrated that the charge separation efficiency of photoanodes can be improved by modifying their surface with polyelectrolyte‐assembled interfacial dipole layers. In principle, rather than polyelectrolytes, one can utilize ferroelectric oxide as a photoelectrode or as a dipole layer for efficient separation of photogenerated charge carriers . However, most ferroelectric oxides (e.g., BaTiO 3 and SrTiO 3 ) are wide bandgap semiconductors and thus, exhibit low utility; they cannot harvest visible light .…”

“…In principle, rather than polyelectrolytes, one can utilize ferroelectric oxide as a photoelectrode or as a dipole layer for efficient separation of photogenerated charge carriers. [48] However, most ferroelectric oxides (e.g., BaTiO 3 and SrTiO 3 ) are wide bandgap semiconductors and thus, exhibit low utility; they cannot harvest visible light. [49] Their application as a dipole layer is also limited due to the following issues: i) lattice-matching between the ferroelectric dipole layers and underlying materials is required, [50,51] ii) a harsh processing condition is required for crystallization and ferroelectricity, [52,53] and iii) formation of additional interfaces between them can cause severe recombination.…”

Freeing the Polarons to Facilitate Charge Transport in BiVO4 from Oxygen Vacancies with an Oxidative 2D Precursor

“…In the present work, we have for the first time employed an oxygen‐rich 2D precursor, BiOIO 3 , as an internal oxidant, to prepare BiVO 4 photoanodes with drastically reduced oxygen vacancies and accelerated polaron hopping. Although BiOIO 3 has been intensively studied in the past decades and found important applications in the photocatalysis area, it has not been used as a precursor to synthesize BiVO 4 until now . The BiOIO 3 precursor has proved to be a strong oxidant owing to its highly oxidative IO 3 − group, which could prevent the formation of vanadium with lower valence.…”