BiFeO3 Nanoparticles Embedded on α-MoO3 Nanorods: A Heterostructure for Oxygen Vacancy-Driven Photocatalytic Activity and Gas Sensing

The rapid development of human civilization has influenced the rising demand for sustainable energy sources, and deteriorating air quality has elevated the risk of toxic-gas exposure. This encourages the development of efficient nanomaterials capable of seamlessly combining multiple functions and adapting to various application areas. However, establishing a generalized strategy for achieving the multipurpose applications of nanomaterials has always been a challenge. Herein, a type-II heterojunction has been designed with BiFeO3 nanoparticles embedded on alpha-MoO3 nanorods to demonstrate highly efficient multifunctional properties for photocatalytic activity and gas sensing. The optimized heterostructure exhibits similar to 8.3-folds higher current density (similar to 12 mu A/cm(2)) and 12-folds enhanced photocatalytic H-2 generation (340 mu mol g(-1)) under visible-light irradiation, surpassing the benchmark for MoO3-based systems. Moreover, 145% improvement in H2S sensing performance (similar to 98% to 100 ppm) with a rapid response/recovery time of 4.7/14 s has been achieved. The proposed growth mechanism suggests that, BiFeO3 nanoparticles sitting on top of alpha-MoO3 nanorods facilitate the formation of interface, creating defects in the system to overcome the shortcomings of bare alpha-MoO3 as a water-splitting catalyst. Band-edge modification (with wide-band-gap alpha-MoO3 nanorods, and narrow-band-gap BiFeO3 nanoparticles) and tuned oxygen vacancy concentration have a synergetic effect on enhanced performance. A potential gradient at the interface of two semiconductors generates a built-in electric field facilitating charge transfer, as reflected in the lower R-ct value. The oxygen vacancies act as electron traps, which reduce the charge recombination and improve visible-light absorption. Consequently, it boosts the photocatalytic efficiency and creates myriads of active sites for H2S adsorption. This work provides a generalized route for designing a band-gap-engineered alpha-MoO3/BiFeO3 heterostructure that exhibits multifunctional activity originated from enriched oxygen vacancies to address the need for green-energy and environmental air-quality monitoring.