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. (C) 2018 Elsevier Ltd. All rights reserved.