Activation of Kagome lattice-structured Cu3V2O7(OH)2·2H2O volborthite via hydrothermal crystallization for boosting visible light-driven water oxidation

Abstract

We report a feasible strategy via hydrothermal crystallization to activate Kagome lattice-structured Cu₃V₂O₇(OH)₂·2H₂O volborthite mineral as a stable visible-light-driven photocatalyst. It was demonstrated to play a crucial role in stimulating absorption ability and photodegradation performance for the removal of methylene blue present in high concentration. In contrast, direct calcination was almost ineffective, whereas post-calcination was significantly detrimental. Moreover, the photocatalytic water oxidation activity of hydrothermally crystallizated volborthite was comparable to that of BiVO₄, and it was clearly higher than those of WO₃ and g-C₃N₄ from aqueous NaIO₃ solution. By further in situ decoration with an optimum amount of CoO_x cocatalysts (i.e., 2 wt%), the oxygen evolution rate of volborthite was greatly enhanced, and it was 1.6-fold, 1.8-fold and 2.9-fold higher than those of BiVO₄, WO₃ and g-C₃N₄, respectively. The importance of hydrothermal crystallization can be elucidated in terms of water-Kagome lattice structure interactions involving built-in intrinsic electric field and formation of single hydrogen bonds.