Photocatalytic properties of Co/Co3O4 films recycled from spent Li-ion batteries

Cobalt recycled from spent Li-ion batteries has been used in the catalysis of azo dye. Metallic cobalt with a compact hexagonal structure was recycled by electrodeposition after leaching a solution of Li-ion battery cathode and applying a potential of − 1.1 V, with charge density = 15 C cm−2 and pH = 2.7. This cobalt, with H2O2 0.27 mol L−1, was used for degradation of azo dye. H2O2 transformed Co in situ into Co3O4 with a spinel-type structure. Co3O4 was confirmed by Raman spectrum bands in the region of 450 and 700 cm−1. The kinetics of the degradation reactions are of first order. Discoloration efficiency of 85% was reached after 210 min under UV radiation. Formation of Co3O4 in situ is an innovative and efficient method to solve two problems: Li-ion battery recycling and azo dye discolorization.