Study on the formation mechanism and catalytic performance of Cu2O coated basic copper salt core-shell catalyst

The core-shell catalysts which have the same composition of Cu2O@Cu4(SO4)(OH)6 were synthesized by the reaction at room temperature(25℃) of copper salts with four kinds of alkalis, include NaOH, Na2CO3, Na2SO3 and Na2S2O3. Thereinto, the sample prepared by Na2S2O3 exhibits the highest catalytic activity. The research results show that the sample prepared by Na2S2O3 possesses many holes and defects in the interior of core, large surface area, rough surface and low crystal compactness, which are beneficial to increase the catalytic activity. There are multiple identities of Na2S2O3 in the reaction. Firstly, Na2S2O3 hydrolyzes to provide OH- group, then disproportionate or react with Cu2+ ion by redox to produce SO42- and S2- ions, which provides SO42- to form Cu4(SO4)(OH)6 crystal. Besides, Na2S2O3 can react with Cu2O core, resulting in the generation of holes in the interior of Cu2O. Hence, the core-shell catalyst which has the composition of Cu2O@Cu4(SO4)(OH)6 and synthesized by Na2S2O3 at room temperature shows very high catalytic activity. It can almost completely degrade high concentration(400 mg/L) of dye(AO7) in the dark in 2h.