Modulating surface charges of bismuth tantalum oxychloride nanoplates for promoting photogenerated charge separation

Abstract

Modulation of anisotropic facets and surface charge properties of semiconductor photocatalysts play significant roles in accelerating the photogenerated charge separation in heterogeneous photocatalysis. Herein, taking Bi₄TaO₈Cl (BTOC) as an exemplar, we demonstrated that the distribution of photogenerated electrons and holes on BTOC can be rationally modulated through surface pretreatment under different pH conditions, resulting in the selective loading of Pd nanoparticles from the top (001) facets to the side (110) facets. The spatial charge separation that occurs between the top and side facets of BTOC was verified, which enables reducing charge recombination and promotes the photocatalytic oxygen evolution (OER) and hydrogen evolution (HER) activity. It was found that Pd nanoparticles selectively loaded on the side (110) facets of BTOC significantly promote the OER activity, while Pd on the top (010) facets exhibits higher HER activity than the side facets. The apparent quantum efficiency (AQE) for photocatalytic OER reaction on the BTOC was measured to be ∼12.2% at 420 nm. The enhanced photocatalytic activity may be due to the synergistic effect of the spatial charge separation and accelerating interface charge transfer between BTOC and Pd nanoparticles. This work provides a beneficial approach for tuning the surface charge properties of semiconductor photocatalysts.