Biomimetic fabrication of WO3 for water splitting under visible light with high performance

Inspired by the high light-harvesting properties of typical butterfly wings, ceramic WO3 butterfly wings with hierarchical structures of bio-butterfly wings was fabricated using a template of PapilioParis butterfly wings through a sol–gel method. The effect of calcination temperatures on the structures of the ceramic butterfly wings was investigated and the results showed that the WO3 butterfly wing replica calcined at 550 °C (WO3 replica-550) is a single phase and has a high crystallinity and relatively fine hierarchical structure. The average grain size of WO3 replica-550 and WO3 powder are around 32.6 and 42.2 nm, respectively. Compared with pure WO3 powder, WO3 replica-550 demonstrated a higher light-harvesting capability in the region from 460 to 700 nm and more importantly the higher charge separation rate, as evidenced by electron paramagnetic resonance measurements. Photocatalytic O2 evolutions from water were investigated on the ceramic butterfly wings and pure WO3 powder under visible light (λ > 420 nm). The results showed that the amount of O2 produced from WO3 replica-550 is 50 % higher than that of the pure WO3 powder. The improved photocatalytic performance of WO3 replica-550 is attributed to the quasi-honeycomb structure inherited from the PapilioParis butterfly wings, providing both high light-harvesting efficiency and efficient charge transport through the WO3