A novel hollow-hierarchical structured Bi₂WO₆ with enhanced photocatalytic activity for CO₂ photoreduction

Converting CO₂ into high-valued chemicals with sunlight is regarded as a promising way to solve the impending energy and environmental crisis. Development of efficient photocatalysts with suitable energy band gap, high stability and favorable structure is thus of very importance. Herein, a novel hierarchical Bi₂WO₆ photocatalyst assembled by Bi₂WO₆ nanosheets with a hollow and rod-shaped appearance has been developed via a facile hydrothermal process. Interestingly, we found that the hydrolysis of Bi(NO₃)₃ in water can produce solid Bi₆O₅(OH)₃(NO₃)₅·3H₂O microrods which can be transformed to hollow-hierarchical Bi₂WO₆ nanosheets by virtue of the Kirkendall effect. The developed Bi₂WO₆ nanosheets exhibit a 58 times higher specific surface area than that of bulk Bi₂WO₆ and a remarkable enhancement in electrochemical performance such as photocurrent and charge transfer. As a result, the hollow-hierarchical structured Bi₂WO₆ photocatalysts achieve a high CH₄ yield of 2.6 μmol g^-1 h^-1, 8 times higher than that of bulk Bi₂WO₆. Moreover, the developed photocatalysts exhibit a high stability during the recycling experiments. This work may present a new strategy to attain hierarchical structured photocatalysts with high activity and stability toward CO₂ reduction.