Carbon-supported Au25 cluster catalysts partially decorated with dendron thiolates: enhanced loading weight and durability for hydrogen evolution reaction

Abstract

In order to establish a design principle for efficient Au electrocatalysis, it is desirable to synthesize a highly loaded, robust, and atomically precise Au cluster catalyst on a conductive carbon support. In this work, heterogeneous Au₂₅ catalysts were prepared by calcining 5.0 wt% of mixed ligated [Au₂₅(D2S)_x(PET)_18−x]⁰ (D2S = second generation Fréchet-type dendron thiolate, PET = 2-phenylethanethiolate) on a carbon support. X-ray absorption fine structure analysis, powder X-ray diffraction, and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) revealed the successful synthesis of carbon-supported partially thiolated Au₂₅ clusters by calcining [Au₂₅(D2S)_10.7(PET)_7.3]⁰ at 425 °C for ≥12 h, whereas calcination of [Au₂₅(PET)₁₈]⁰ under the same conditions resulted in thermally induced aggregation into larger Au nanoparticles. The D2S-modified Au₂₅ catalyst showed better durability than PET-modified Au₂₅ in electrocatalytic hydrogen evolution reaction. The higher durability was attributed to the suppression of aggregation of Au₂₅ clusters during the reaction, as confirmed by AC-HAADF-STEM. These results indicate that the residual D2S ligands on Au₂₅ enhance the stability against aggregation more than the residual PET due to stronger non-covalent interactions with carbon supports and/or greater steric hindrance of dendritic structure. This work demonstrates that the stability of Au catalysts can be improved by partial decoration with designed ligands.