Ultra-small Pd clusters supported by chitin nanowires as highly efficient catalysts

For the first time, chitin microspheres woven from nanowires with multi-scale porous structures were used as an excellent support for a catalyst of ultra-small Pd clusters. The Pd species anchored on the precursor Pre-Pd@chitin were 0.6 nm in average size, while the reduced catalyst Red-Pd@chitin featured ultra-small particles of 1.3 nm in average size. X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) demonstrated that the Pd catalyst in both oxidative and reductive states retained good dispersity and ultra-small clusters. The catalyst was tested for the hydrogenation of p-nitroanisole, exhibiting an excellent initial rate (13× that of commercial Pd/C)and excellent turnover frequency reaching 52, 000 h^-1. Furthermore, the catalyst could be recycled and used more than 10 times with no decay of the catalytic activity, suggesting potential industrial applications.