Nitrate anion-mediated morphology control of Bi5O7NO3 and its photocatalytic activity

Different morphologies of a material often show different performance. Four different morphologies of Bi5O7NO3 including microflowers, nanowires, nanoribbons and nanosheets have been controllably synthesized by simply increasing concentration of precursor bismuth nitrate in a hydrothermal method without adding any surfactant or template. Those morphologies have revealed a dramatic difference in rhodamine B (RhB) photocatalytic activity. The nanosheets showed much better photocatalytic activity than the nanowires and the nanoribbons while the microflowers showed very poor activity. In our control experiments where we partially substituted Bi(NO3)3 for Zn(Ac)2, Zn(NO3)2, and KNO3 respectively, we have found that the formed morphologies were very closely related to nitrate anions. This explicitly proves that the nitrate anion plays a crucial role in determining the morphologies. Guided by atomic model, nitrate anion-mediated oriented attachment mechanism is proposed on the basis of our experimental results. Our finding that nitrate anions favoured the formation of nanosheets would benefit the synthesis of nanosheets at a lower cost. Our study provides a simple and economic way for preparing good candidates for potential applications in solar energy conversion.