Small Organic Molecule Based Photoelectrodes for Efficient Photoelectrochemical Cathodic Protection

Photoelectrochemical cathodic protection (PECCP) as a branch of photocatalysis and photoelectrochemistry holds great promise for efficient anticorrosion. Organic semiconductors with tunable bandgaps and favorable optoelectronic properties have been attracting more attention in the photoelectrochemical (PEC) field. However, its application for PECCP has been marginally explored. Herein, we successfully fabricated a small organic molecule (ITIC: 3,9-bis(2-methylene-(3-(1,1- dicyanomethylene)-indanone))-5,5,11,11tetrakis(4hexylphenyl)-dithieno[2,3-d:2,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene) based photoelectrode for PECCP of 304 stainless steel (304SS). The PEC research proved that it could provide PECCP for 304SS with a photoinduced potential drop of 100 mV. A molecular structure design strategy was also adopted to broaden the light absorption spectrum of ITIC by halogenating the terminal group with the Cl atom. The obtained ITIC derivate (IT-2Cl)-based photoelectrode provided a higher photoinduced potential drop of 150 mV for PECCP of 304SS. More impressively, the separation of photoinduced electron–hole pairs was promoted and the electron transportation was accelerated, when introducing TiOx thin film as the electron acceptor and electron transportation channel in the photoelectrode. Consequently, the PECCP for 304SS was dramatically enhanced, with the potential drop increasing to 290 mV. The flexible molecular design strategy and improved PECCP performance proposed a guideline for the potential applications of organic semiconductor-based photoelectrodes in the PECCP field.