Characterization of site-isolated iridium atoms supported on reduced graphene aerogel at an exceptional Ir loading of 23.8 wt% with synchrotron and electron microscopy techniques

Abstract

Atomically dispersed supported metal catalysts provide substantial advantages when compared to their traditional counterparts. They offer 100% dispersion of expensive noble metals, exhibit intriguing catalytic properties, and provide insights into the relationship between structure and catalytic activity [1]. However, there are several challenges these novel class of catalysts are facing, such as their limited stability in reaction environment and limited metal loadings (typically below 1 wt%). To overcome these issues, we have used a novel and promising support, reduced graphene aerogel (rGA), consisting of numerous bonding sites for Ir, having a significantly high surface area (>700 m2 /g), and great electronic properties. Thanks to these outstanding features of rGA, we achieved an exceptional Ir loading of 23.8 wt%. The presence of individual Ir atoms at such high loading on the surface of rGA was confirmed by combining atomic-resolution images obtained using a Hitachi HF5000 Cs-corrected cold FEG aberrationcorrected scanning transmission electron microscope and X-ray absorption spectroscopy data. These findings highlight rGA's potential as an exceptional support material for expensive noble metal complexes to achieve extraordinary loadings in atomically dispersed supported metal catalysts.