Enhanced visible light-driven activity of TiO2 nanotube array photoanode co-sensitized by "green" AgInS2 photosensitizer and In2S3 buffer layer

The AgInS₂/In₂S₃ nanoparticles (NPs) co-sensitized TiO₂ nanotube array (NTA) photoanodes with high photoelectrochemical (PEC) conversion efficiency are prepared and optimized. The In₂S₃ buffer layer around AgInS₂ absorber layer significantly improves the charge generation/separation efficiency of the prepared photoanode. Compared with single AgInS₂ NPs sensitized TiO₂ NTAs, the design of the AgInS₂/In₂S₃ heterojunction NPs sensitized TiO₂ NTAs further promotes the charge transfer in the system, and avoids the unmatched energy band alignment between AgInS₂ and TiO₂. The AgInS₂(3)/In₂S₃(5) NPs co-sensitized TiO₂ NTAs possess the best PEC conversion performance. The AgInS₂ and In₂S₃ NPs distribute uniformly on TiO₂ NTAs to form close interfacial adhesion. Simultaneously, the one-dimensional TiO₂ nanotubes serve as the direct electron pathways and ensure the rapid collection of charge carriers generated by the system. Moreover, due to the more negative Fermi levels and energy band potentials of AgInS₂ and In₂S₃, the prepared TiO₂ NTA/AgInS₂(3)/In₂S₃(5) photoanode also exhibits an excellent PEC cathodic protection performance for 316L stainless steel in NaCl solution.