Homoepitaxial growth on semiconductor nanocrystals for efficient and stable visible-light photocatalytic hydrogen evolution

Recent advancements in colloidal chemistry offer unique opportunities to construct core/shell semiconductor nanocrystals (NCs) with tailored optical properties. Major efforts have been focused on synthesizing core/shell NCs via heteroepitaxial growth, which often leads to effective surface passivation and thus reduced trap states (TS). However, the growth of a shell with a wider band gap or energy band offset tends to form a physical barrier for the migration of photo-generated charge carriers to the surrounding environment, resulting in compromised photoactivity. Here, we show that the homoepitaxial growth of NCs is able to facilitate the passivation of TS without affecting the migration of charge carriers to the surface of NCs. Homostructured CdS_homo NCs have demonstrated improved photocatalytic hydrogen production compared with the CdS core NCs and heterostructured CdS/ZnS core/shell NCs in terms of both efficiency and photostability. We envision that homoepitaxial growth would provide new opportunities to tailor semiconductor NCs for photocatalytic and photovoltaic applications.