Type-Ⅰ hetero-junction of BiOI-BiO2-x anchored on Ni foam accelerating charge separation and transfer for efficiently purifying hazardous wastewater

Photo-induced electrons will flow from CB edge of BiOI to that of BiO 2-x , then to Ni foam. The photo-generated holes will migrate from VB edge of BiOI to that of BiO 2-x . Photo-excited electrons on the Ni foam react with O 2 to generate ·O 2 – . Then, ·O 2 – further reacts with H + to produce ·OH. RhB was decomposed by h + , ·O 2 – and ·OH. • A novel photocatalytic film of BiOI-BiO 2-x /Ni foam was successfully constructed. • Ni foam accelerated electron transfer and enhanced stability of BiOI-BiO 2-x powder. • The BiOI-BiO 2-x = 1:3/Ni foam exhibited eximious photocatalytic performances. • The RhB was decomposed by h + , ·O 2 – and ·OH. About 70 mg of BiOI-BiO 2-x powder was attached to Ni foam. Compared to BiOI/Ni foam and BiO 2-x /Ni foam, the BiOI-BiO 2-x /Ni foam exhibited distinctly enhanced photocatalytic activity for removing RhB from water. Among them, the BiOI-BiO 2-x = 1:3/Ni foam demonstrated the optimal photocatalytic activity. Around 97% of RhB was decomposed over BiOI-BiO 2-x = 1:3/Ni foam under 7 h irradiation of a 300 W xenon lamp, which was 47.5 times that over BiOI/Ni foam and 1.3 times that over BiO 2-x /Ni foam, respectively. The degradation rate constant (k) of RhB over BiOI-BiO 2-x = 1:3/Ni foam was 71.8 times that over BiOI/Ni foam and 2.6 times that over BiO 2-x /Ni foam, respectively. The removal rates of TOC and TON in the BiOI-BiO 2-x = 1:3/Ni foam solution were approximately 50% and 29%, respectively. Photo-induced electrons and holes flowed from BiOI to BiO 2-x and then photo-generated electrons of BiO 2-x further transferred to Ni foam. The separation efficiency of carriers in BiOI-BiO 2-x = 1:3/Ni foam was greatly improved, thereby enhancing its photocatalytic activity. In addition, the improved photocatalytic activity of BiOI-BiO 2-x = 1:3/Ni foam was ascribed to its strong adsorption capacity. The mainly active species for RhB degradation were holes (h + ) and superoxide radicals (·O 2 – ).