Cofactors such as nicotinamide adenine dinucleotide (NADH) and its phosphorylated form (NADPH) play a crucial role in natural enzyme-catalyzed reactions for the synthesis of chemicals. However, the stoichiometric supply of NADH for artificial synthetic processes is uneconomical. Here, inspired by the process of cofactor NADPH regeneration in photosystem I (PSI), catalyst-modified photocathodes are constructed on the surface of polythiophene-based semiconductors (PTTH) via self-assembly for photoelectrochemical catalytic NADH regeneration. With the assistance of viologen (vi