Facile construction of BiOI/Nb2O5 heterojunction films and their excellent photocatalytic activity

A conventional hydrothermal method followed by a facile immersion method is used to prepare BiOI/Nb 2 O 5 heterojunction films on the wire mesh made of stainless steel. The results show that sea urchin-like Nb 2 O 5 nanospheres of orthorhombic structure and hierarchical flower-like BiOI with a tetragonal crystal type were formed in the preparation. BiOI and Nb 2 O 5 combined firmly at the micron and nanoscale. They have formed heterojunctions. The optical measurements show that the heterojunction formation markedly extended the visible light absorption wavelength range even to 600 nm. The optical band gap values of the BiOI/Nb 2 O 5 heterojunction films were decreased from 3.05 to ~ 1.63 eV. PL spectra revealed the heterojunction formation significantly inhibited the recombination of photogenerated electron–hole pairs. The electrochemical testing suggests that the photocurrent density of the BiOI/Nb 2 O 5 heterojunction films is nine times that of the individual Nb 2 O 5 film at most. It means that the heterojunction observably improved the separation efficiency of photogenerated charges. Based on the above strategy, the photocatalytic activity in degrading RhB dye in an aqueous solution was enhanced by 6.2 times at most. When the immersion number was 12, the heterojunction film exhibited the most excellent photocatalytic activity. A possible mechanism of photocatalytic performance improvement was also discussed.