Hierarchical CuS Hollow Microspheres Decorated with Au Nanoparticles and Their Enhanced Photocatalytic Degradation of Methylene Blue

Abstract Considerable attention has been devoted to decorating CuS materials with Au nanoparticles (NPs) for enhanced optoelectronic properties. However, most resulting CuS substrates remain solid nanomaterials prone to aggregation. The construction of hierarchical CuS hollow microspheres (CuS HHMSs) and their decoration with Au NPs is thus desirable, as such composites combine microscale structural stability with nanoscale activity yet remain unexplored. Here, a two-step method is developed for preparing CuS-Au HHMSs via a wet chemical reaction of HAuCl4 in an aqueous solution containing solvothermally synthesized CuS HHMSs. The CuS HHMSs consist of nanosheets with ∼2 μm average diameter and ∼240 nm shell thickness. The obtained CuS-Au HHMSs feature polycrystalline Au NPs decorated on the surface edges of the spherical shells with their size readily tunable by adjusting the amount of HAuCl4 added. The typical CuS-Au HHMSs, obtained with 0.3 mL of HAuCl4 (25 × 10–3 mol/L) added, exhibit enhanced visible-light absorption and a narrower optical band gap compared to bare CuS HHMSs. When applied to methylene blue (MB) degradation under light irradiation, these CuS-Au HHMSs demonstrate a degradation kinetic constant of ∼0.104 min–1 along with a notably high activity factor of ∼10.4 min–1 g–1, outperforming both pure CuS HHMSs and CuS-Au HHMSs obtained with higher or lower amounts of HAuCl4 added. Furthermore, they can maintain high activity over five consecutive cycles with minimal loss, showing excellent recyclability. The enhanced photocatalytic performance is attributed to the improved separation of photogenerated charge carriers induced by Au decorations, along with the structural stability and high activity of the CuS HHMS substrate. This work offers a facile route to CuS-Au HHMSs with high photocatalytic performance for MB degradation.