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

About 70 mg of BiOI-BiO2-x powder was attached to Ni foam. Compared to BiOI/Ni foam and BiO2-x/Ni foam, the BiOI-BiO2-x/Ni foam exhibited distinctly enhanced photocatalytic activity for removing RhB from water. Among them, the BiOI-BiO2-x = 1:3/Ni foam demonstrated the optimal photocatalytic activity. Around 97% of RhB was decomposed over BiOI-BiO2-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 BiO2-x/Ni foam, respectively. The degradation rate constant (k) of RhB over BiOI-BiO2-x = 1:3/Ni foam was 71.8 times that over BiOI/Ni foam and 2.6 times that over BiO2-x/Ni foam, respectively. The removal rates of TOC and TON in the BiOI-BiO2-x = 1:3/Ni foam solution were approximately 50% and 29%, respectively. Photo-induced electrons and holes flowed from BiOI to BiO2-x and then photo-generated electrons of BiO2-x further transferred to Ni foam. The separation efficiency of carriers in BiOI-BiO2-x = 1:3/Ni foam was greatly improved, thereby enhancing its photocatalytic activity. In addition, the improved photocatalytic activity of BiOI-BiO2-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 (·O2–).