Disclosed herein methods for combating biofouling in a liquid, e.g. an aqueous medium by providing a surface coated with at least one laser-induced graphene (LIG) layer in said liquid medium. Particularly disclosed herein method and devices for treating water comprising passing a water stream through a membrane module equipped with at least one spacer coated with at least one layer of LIG, and optionally by applying an electric potential to the at least one LIG layer to achieve a bactericidal effect in the water stream. Specifically, disclosed herein a polymeric mesh suitable for use as a spacer in a membrane module in water treatment application, said mesh being at least partially coated with LIG.