Either conventional or ionic carbon nitride films were directly deposited onto conductive substrates, or PCN was deposited onto porous metal oxide (e.g., TiO2 or ITO) films acting as a scaffold and an effective n-type electron collector . In a similar vein, PCN-based photocathodes have been fabricated either as pristine or biopolymer-activated films, or in combination with p-type semiconductors (e.g., CuGaSe2 , CuI or NiO ) acting as effective hole collectors.