Synergistic Enhancement of Piezocatalytic Activity of BaTiO3 Convex Polyhedrons Nanocomposited with Ag NPs/Co3O4 QDs Cocatalysts

Piezocatalysis is one of the green and promising catalytic technologies for the degradation of organic pollutants. Surface modifications such as exposed facet engineering and surface decoration of nanoparticles (NPs) are simple but useful enhancement strategies for a catalytic system. However, the synergistic effect and mechanism of facet engineering and dual-cocatalyst decoration on piezocatalytic activity are still ambiguous and more investigations are expected. Herein, the piezocatalytic activities of BaTiO3 (BTO) polyhedrons with anisotropic {001} and {110} facets and BTO cubes with isotropic {001} facets were compared. Furthermore, BaTiO3 (BTO) convex polyhedrons with selectively deposited Ag NPs and uniformly loaded Co3O4 quantum dots (QDs) are rationally synthesized through photochemical deposition. The individual and synergistic effects of Ag NPs and Co3O4 QDs on the piezocatalytic activities are systematically studied. It was found that dual-cocatalyst-modified BTO possesses the highest piezocatalytic activity in methyl orange degradation, with a reaction constant k of 0.0539 min-1, around 5, 2.2, and 1.3 times higher than that of nonmodified and Ag NP- and Co3O4 QD-modified BTO, respectively. Moreover, dual-cocatalyst-decorated BTO also exhibits excellent piezocatalytic performance in nondye pollutant degradation, with ∼100% tetracycline hydrochloride decomposed in 60 min. By analyzing the contribution, quantifying the amount of different free radicals, and comparing the chemical states of surface elements before and after piezocatalytic measurements, it was inferred that facet-dependent Ag NPs acted as efficient electron-transport sites, while uniformly loaded Co3O4 QDs served as hole-transfer sites to fully facilitate the migration of electrons and holes in a piezocatalytic reaction. This research presents a rational and effectual modification strategy to enhance the piezocatalytic activity of piezocatalysts and gives a thorough discussion of the enhanced mechanism.