Dark formation of reactive oxygen species by bifunctional copper doped sodium bismuthate: Direct oxidation vs catalytic oxidation of organic pollutants.

Sustained generation of reactive oxygen species for aquatic decontamination is desired, but the strategies aiming at this goal usually involve tremendous input of chemicals or energy, which for practical purpose have hindered their implementation. Here we propose a very simple approach for degrading organic pollutants based on copper doped sodium bismuthate (CSB), in which reactive oxygen species can be continuously generated requiring no irradiation or other chemicals. The material was easily prepared by coprecipitation of NaBiO3·nH2O and Cu(NO3)2. Two stages of cyclic degradation of organic pollutant in sequence by the same CSB powder, alone with series of characterization measurements and control experiments were designed. CSB mediated reaction proceeds via two distinct mechanisms viz. direct oxidation and catalytic oxidation, each involving different primary reactive species and resulting in different product profiles. Direct oxidation occurs accompanied by the structural transformation of CSB involving singlet oxygen, originated from lattice oxygen, as the responsible species, while catalytic oxidation employs dissolved oxygen to primarily yield superoxide radical owing to the presence of oxygen vacancy. Our findings provide novel insights into the direct and catalytic oxidative activity of CSB, and suggest a based-on approach for simple, efficient and sustained generation of reactive species for water treatment.