Sol-gel synthesis of lithium-holmium co-doped cobalt ferrite integrated on carbon nanotubes for enhanced photodegradation efficacy

Rapid industrialization, over-population and urbanization lead to pollution, mainly water pollution. Semiconductor photocatalysis is one of the most versatile physio-chemical techniques to get rid of organic based impurities present in water. Among several types of transition metal oxides, the cobalt ferrite and its derivatives serve as photocatalyst for water remediation, however they lack efficiency due to unfavorable bandgap and surface area. To overcome this issue, doping of cobalt ferrites with alkali metal (Li) as well as with rare earth metal (Ho) is performed, which in turn tuned the optical bandgap. The optimized optical bandgap by dual metal ions doping philosophy, the cobalt ferrite yielded the enhanced the photocatalytic efficacy. Undoped and Li-Ho-co-doped cobalt ferrite (LCHFO) was synthesized via sol-gel route. To further strengthen the photodegradation performance, sol-gel synthesized co-doped cobalt ferrite particles were integrated with carbon nanotubes (CNTs). The carbon nanotubes played two roles for increased photocatalysis efficiency. First, they enhanced capturing ability of the photogenerated electrons. Secondly, the CNTs enhanced the surface area and number of active sites for the adsorption of organic pollutant molecules. LCHFO@CNTs showed remarkable photodegradation of 94.12%, 86.6%, and 92.48% for diclofenac, rhodamine-B, and congo red, respectively.