Construction of Ultrathin CuAuAg Nanosheet-Assembled Three-Dimensional Nanoflowers for Photothermal Conversion and Electrocatalytic Hydrogen Evolution

Ultrathin two-dimensional (2D) nanostructures, with superhigh exposure of the under-coordinated metal atoms relative to large-sized quasi-spherical particles or bulk counterparts, have shown enormous potential to enhance various heterogeneous catalytic reactions. The creation of in-plane holes and rational assembling of ultrathin 2D nanosheets into 3D hierarchical architectures can prevent the restacking issue of nanosheets, thereby providing more active sites by hampering atomic diffusion, nearby nanosheet aggregation, and thermodynamic structural reform. Herein, we report the stepwise construction of ultrathin CuAuAg nanosheet-assembled 3D nanoflowers (NFs). The synthesis involves the conversion of Au@Cu x O mesoporous nanospheres into CuAg NFs, followed by a controlled galvanic replacement reaction with chloroauric acid to create holes and manipulate the atomic ratio between Cu, Au, and Ag. With strong broad-spectrum light absorption across the UV–vis region, the current CuAuAg NFs exhibited satisfactory photothermal conversion under Xe lamp irradiation. When serving as HER electrocatalysts, the Cu 10.5 Au 58.4 Ag 31.1 NFs displayed the optimized performance in terms of overpotential and activity, surpassing the Cu 71.4 Ag 28.6 NFs and Au NCs, which is supported by DFT simulations, showcasing the multimetallic coupling advantage for HER. This study presents a viable route to construct trimetallic 3D hierarchical nanostructures and validates their application in photothermal conversion and electrocatalytic HER, guiding the design of high-performance photosensitizers and electrocatalysts.