Au nanoparticle-doped Co3O4-CoFe2O4@SiO2 as a catalyst for visible-light-driven water oxidation

We proposed a facile method to systematically fabricate Co-based oxides as water oxidation catalysts (WOCs) for oxygen evolution under visible light irradiation. The results suggested that as-prepared Co3O4-CoFe2O4, Co3O4-CoFe2O4@SiO(2 )and Co3O4-CoFe2O4@SiO2@Au are excellent catalysts for the water oxidation reaction, while Co3O4-CoFe2O4@SiO2@Au shows the best catalytic activity, and an O-2 yield of 71.24% can be obtained. To gain insights into the relationship between the structural details and functional behaviors, the as-prepared catalysts were characterized using various analytical tools, respectively. SEM and TEM analyses showed that the average size of the nanoparticles was about 500 nm for the three catalysts and the surface of the Co3O4-CoFe2O4 catalyst was covered by a floc layer of SiO2. XRD and EDS studies confirmed that Au nanoparticles were present in Co3O4-CoFe2O4@SiO2 nanocomposites. From the above experimental results, we concluded that the reason why Co3O4-CoFe2O4@SiO2@Au shows superior performance over the other two catalysts Co3O4-CoFe2O4 and Co3O4-CoFe2O4@SiO2 may be due to: (1) the large refractive index and low dielectric constant of SiO2 (epsilon = 1.56); (2) Au metal nanoparticles can effectively harvest a wide range of sunlight containing UV light and visible light because of its plasmonic effect. Our research showed that Co3O4-CoFe2O4@SiO2@Au can be used as an efficient catalyst for water oxidation under visible light irradiation.