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

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 Au-25 catalysts were prepared by calcining 5.0 wt% of mixed ligated [Au-25(D2S)x(PET)(18-x)](0) (D2S = second generation Fr & eacute;chet-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 Au-25 clusters by calcining [Au-25(D2S)(10.7)(PET)(7.3)](0) at 425 degrees 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 Au-25 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 Au-25 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.