Controlling the Core-Shell Structure of CuS@CdS Heterojunction via Seeded Growth with Tunable Photocatalytic Activity

We report the seed-mediated synthesis of CuS@CdS core-shell heterojunction with diverse morphologies by introducing kinetic control. By using CuS nanoplates as seeds and a collective manipulation of the injection rate of Cd²⁺ precursor with a syringe pump and the reaction temperature, two distinctive growth modes, i.e., island and layer-by-layer modes, respectively, could be realized. It is found that the growth is, in principle, determined by the deposition rate relative to the diffusion rate of the CdS growth monomers. Specifically, at a high injection rate and a relatively low reaction temperature, the deposition of CdS monomers on the surface of the CuS nanoplate follows an island growth mode because of the lattice mismatch between CuS and CdS and distinct binding energies of them. We can facilitate surface diffusion of these deposited monomers by reducing the injection rate of Cd²⁺ and increasing the reaction temperature. In this case, growth can be switched to a layer-by-layer mode. The products are found with tunable and significantly improved photocatalytic performance toward dye degradation and H₂ production from water under visible-light irradiation in comparison to the sole use of either CdS or CuS photocatalyst. This work provides an effective approach to the rational design of heterojunctions.