Polydopamine nanolayer assisted internal photo-deposition of CdS nanocrystals for stable cosensitized photoanode

Hydrogen evolution via photo-electro-chemical (PEC) co-catalysis is potential for solving energy crisis and environmental issues. The rapidly advances of fabrication and broad applications of polydopamine (PDA) and its derivatives have drawn intense attentions in recent years. Herein, an ultrathin PDA coating with nanometer accuracy was conformally grown on TiO2 nanotube arrays (NTAs) via electrochemical polymerization, in which the polymer provided a platform for further photoinduced assembly of CdS nanocrystals in the embedded mode. The optimized CdS@PDA/TiO2 NTAs hierarchical heterostructure as photoanode gave an excellent PEC performance and exhibited outstanding stability under light irradiation. The photocurrent density was heightened to 5.48 mA·cm−2, which was beneficial to H2 evolution with a rate of 20 µmol·h−1·cm−2. The improvement of PEC activity was ascribed to co-photosensitization, optimized carriers transfer, and transport route arised from CdS embedding, resulting to provide a persistent driving force for charge separation based on secure heterojunction of CdS/TiO2 glued by PDA. The improvement of PEC stability was due to the inhibition of CdS photocorrosion covered by PDA shelter. This advance boded well for the development of PEC field founded on multifunctional PDA.