Enhancing visible-light photocatalytic activity of hard-biotemplated TiO2: From macrostructural morphology replication to microstructural building units design

Highlight• A new strategy of syntheses to control microstructure of biotemplated TiO₂. • Macrostructural morphology assembled by designed microstructural building units. • Concave porous microstructures markedly enhance the photocatalytic efficiency. • Twenty-fold higher photocatalytic degradation of tetracycline than pure TiO₂. • Photocatalytic efficiency is 5.5 times higher than conventional biotemplated TiO₂. Biotemplating technique using hard templates is an effective strategy to prepare visible light-activated TiO₂ inherited macrostructural morphologies and self-doping elements from templates. However, conventional hard biotemplating method for preparing TiO₂ focused only on replicating the macrostructural morphology of templates via the sol-gel method, and neglected the effect of microstructural building units for artificial macrostructure assembly. Generally, the microstructural building units of the final macrostructural morphology are tightly packed nanoparticles. This paper presents a newly designed solvothermal method to replace the microstructural building units from tightly packed nanoparticles to convex nanowires or concave pores. This strategy can achieve the leap of conventional hard biotemplating method from macrostructure replication to microstructural building units design. The hard-biotemplated TiO₂ with designed microstructure exhibited significantly further enhanced visible-light photocatalytic efficiency in tetracycline degradation due to the increase of active sites, high separation efficiency of photo-generated electrons and reducing the charge-transfer resistance. Biotemplated TiO₂ with concave porous microstructural building units is 22.0, 5.5 and 4.4 times higher than those of pure TiO₂ and the two biotemplated TiO₂ samples prepared via conventional sol-gel method and solvothermal method without glycerol or HF added, respectively. The enhanced visible-light photocatalytic efficiency by microstructure design was also demonstrated by using ciprofloxacin.