Bio-mimicking TiO₂ architectures for enhanced photocatalytic activity under UV and visible light

Abstract

Green leaves are responsible for natural photosynthesis in plants and their unique structures offer the most efficient blueprint for artificial materials in terms of solar energy capture and utilisation. The full architecture of the leaf photosystem was successfully replicated at both the nano and micro levels using biotemplating with TiO₂. This approach resulted in a highly porous structure that can be used as a photocatalyst with enhanced properties such as improved visible light-harvesting ability. Scanning and transmission electron microscopy images of the final products confirmed that the detailed microscale framework and nanostructures, such as the chloroplast and the thylakoids were well replicated. Biotemplated artificial TiO₂ leaves with the architecture of Camellia tree leaves outperformed well-known P25 TiO₂ in photocatalytic degradation of methylene blue dye under visible light: more than twofold in the case of blue (440 nm) and ca. one and a half times under green (515 nm) light. Also, the carbon dioxide yield of photocatalytic oxidation of ethanol catalysed by the biotemplated TiO₂ material was approximately 1.3 times higher than the CO₂ produced by P25 under green light. We attributed this enhanced visible light photocatalytic performance to the light-harvesting features and to the high surface area imparted by the interconnected nanosheets (replicating the thylakoids) resulting from our improved biotemplating method. The method reported in this work presents a facile route for the production of synthetic inorganic materials which possess morphologies similar to that present in the natural template materials.