Ferroelectrics in photocatalysis

The rapid development of industrialization and population brings water and air pollution and energy crisis. Solar driven catalysis is expected to relieve above issues. However, low efficiency of solar conversion limited by poor light harvesting and serious charge recombination of semiconductors and high surface reaction barriers is far from the satisfactory of industrial request. Ferroelectrics have been considered as promising photocatalysts to overcome these shortcomings. Herein, perovskite ferroelectrics such as BaTiO 3 , PbTiO 3 and LiNbO 3 , layered bismuth-based ferroelectrics like BiFeO 3 , Bi 2 WO 6 , Bi 2 MoO 6 , etc. and other ferroelectrics have been introduced, and their crystal structure, polarity source and synthetic method have been highlighted. Then, the research progress of ferroelectrics for photocatalysis has been summarized, including pollution degradation, water splitting and CO 2 reduction. Finally, the current challenges and future prospects of ferroelectric photocatalysts have been provided. The purpose of this review is not only to provide a timely summary for the application of ferroelectrics in photocatalysis, but also to present a deep insight and guideline for the future research works of ferroelectrics .

Crystallinity-dependent photodegradation of metallic Bi in situ grown on perovskite Bi3TiNbO9 nanosheets toward antibiotic

Owing to its wide band gap of ~3.2 eV, perovskite Bi₃TiNbO₉ only absorbs the solar spectrum in the ultraviolet range, which restricts its use as an effective photocatalyst. Here, a controllable and facile reduction strategy was adopted to promote the in-situ growth of metallic Bi in perovskite Bi₃TiNbO₉ nanosheets. The in-situ growth of metallic Bi extended photoresponse to cover the whole visible region. Adsorption of tetracycline hydrochloride (TC-H) on the surface of Bi₃TiNbO₉ with in-situ growth of metallic Bi (BTNO_OV-Bi⁰) was dramatically enhanced, while BTNO_OV-Bi⁰ exhibited a superior photocatalytic performance for tetracycline hydrochloride (TC-H) degradation under visible light irradiation with the degradation rate of 5 times higher than that of pristine Bi₃TiNbO₉. Moreover, the degradation activity was strongly dependent on the crystallinity of metallic Bi phase in BTNO_OV-Bi⁰ samples. On the basis of experiment results, the visible-light driven catalytic mechanism of BTNO_OV-Bi⁰ was elucidated. Besides, the in-situ growth of metallic Bi was also introduced in perovskite Bi₅FeTi₃O₁₅, resulting in an enhanced photocatalytic activity, which indicated an enormous potential of this strategy in semiconductor structure tuning. Our study provides an effective approach to boost the performance of photocatalysts for solar-energy conversion.

Photocatalysis Enhanced by External Fields

The efficient conversion of solar energy by means of photocatalysis shows huge potential to relieve the ongoing energy crisis and increasing environmental pollution. However, unsatisfactory conversion efficiency still hinders its practical application. The introduction of external fields can remarkably enhance the photocatalytic performance of semiconductors from the inside out. This review focuses on recent advances in the application of diverse external fields, including microwaves, mechanical stress, temperature gradient, electric field, magnetic field, and coupled fields, to boost photocatalytic reactions, for applications in, for example, contaminant degradation, water splitting, CO₂ reduction, and bacterial inactivation. The relevant reinforcement mechanisms of photoabsorption, the transport and separation of photoinduced charges, and adsorption of reagents by the external fields are highlighted. Finally, the challenges and outlook for the development of external-field-enhanced photocatalysis are presented.