Charge Redistribution in Nise₂/Mos₂ n–n Heterojunction Towards the Photoelectrocatalytic Degradation of Ciprofloxacin

Abstract

This study reports the photoelectrocatalytic (PEC) activity of a n–n heterojunction comprising MoS2 and NiSe2. The synthesis of the composite was achieved through a facile solvothermal method, yielding an exfoliated MoS2 layered sheet loaded with NiSe2 nanoparticles. Under visible light radiation and an external electric field, the obtained composite NiSe2/MoS2 exhibited enhanced catalytic activity for ciprofloxacin (CIP) degradation. The NiSe2/MoS2 heterojunction achieved about 78% degradation efficiency with a first-order kinetic rate of 0.0111 min-1, compared to 38% efficiency and a first-order kinetic rate of 0.0044 min-1, observed for MoS2. The NiSe2/MoS2 heterojunction was more advantageous due to the synergy of charge carrier induction by visible light radiation and improved charge carrier separation induced by the external electric field. The formation of n–n heterojunction at the interface of the two materials resulted in charge redistribution in the materials, with a simultaneous realignment of the band structure to achieve Fermi energy equilibration. The primary reactive species responsible for CIP degradation was identified as the photo-induced h+. Furthermore, the catalyst exhibited high stability and reusability, with no significant reduction in activity observed after five experimental cycles. This study reveals the potential of exploring the synergy between the photocatalytic and electrocatalytic processes in removing harmful pharmaceutical compounds from water.