Selective cation exchange in colloidal Janus-type Cu_2-xS/CuInS₂ heteronanorods for boosting photocatalytic hydrogen...

Ideal photocatalysis generally exhibits several key characteristics, including broad-spectrum light absorption, efficient electron-hole separation and transfer, excellent photocatalytic activity, and appropriate band alignment. To date, strategies for enhancing photocatalytic performance focus on surface modification, introduction of co-catalyst or doping, and heterostructure engineering. In this work, we aim to improve the photocatalytic activity of Cu_2-xS by constructing heteronanostructure combined with ion doping. Through a two-step seeded-growth method, we successfully synthesized Janus-type Cu_2-xS/CuInS₂ heteronanorods with well-defined architectures for hydrogen production from solar water splitting. Three types of cations (Cd²⁺, Zn²⁺, Ga³⁺) were selected as dopants to further enhance the photocatalytic activity. Intriguingly, those foreign cations exhibit distinct doping behaviors in Janus-type heteronanorods, by either diffusing into Cu_2-xS tips, CuInS₂ tails, or across the whole nanorods. These selective doping behaviors originate from the miscibility of foreign cations with the parent nanocrystals and the lattice strain of possible products with respect to the template heteronanorods. The incorporation of foreign cations effectively alters the band alignment of the Cu_2-xS/CuInS₂ heteronanorods, thereby improving their photocatalytic hydrogen evolution performance. The Cd-Cu_2-xS/CuInS₂ heteronanorods exhibited excellent photocatalytic activity under visible light irradiation, with a hydrogen evolution rate of 1265.7 µmol·h^-1·g^-1, which is 83 times higher than that of the original Cu_2-xS/CuInS₂. This work provides new insights into the selective doping behavior in copper chalcogenide nanomaterials and opens up pathways for enhancing the hydrogen evolution activity of other related multicomponent photocatalysts.