Crystallinity control on Bi2MoO6 microspheres for improved photocatalytic oxygen evolution

Crystallinity of the photocatalyst has a profound impact on its reactivity. Here, flower-like Bi₂MoO₆ microspheres were synthesized via a solvothermal method and subsequently calcined at varying temperatures to regulate the crystallinity and particle size. The thermally treated samples exhibited enhanced photocatalytic oxygen evolution compared to the pristine Bi₂MoO₆. Higher calcination temperatures led to the formation of larger crystallites, significantly boosting the activity. We demonstrate that crystallinity, rather than surface area, plays a more vital role in governing the photocatalytic performance of Bi₂MoO₆. Improved crystallinity can thicken the space charge layer (SCL), resulting in a greater band bending that facilitates the separation of electron-hole pairs. Conversely, poor crystallinity leads to an abundance of surface and bulk defects, promoting electron-hole recombination. Overall, efficient charge separation and suppressed recombination endow the calcined Bi₂MoO₆ with enhanced water oxidation efficiency.