Synergistic Effects for Enhanced Catalysis in a Dual Single-Atom Catalyst

Synergistic effects have been discussed extensively in bimetallic heterogeneous catalysis, but it remains unclear how the effects function at the atomic scale. Here, we report a dual single-atom catalyst (DSAC) Ir 1 Mo 1 /TiO 2 displaying much greater catalytic chemoselectivity (>96%, at 100% conversion) than comparable single-atom catalysts (SACs) Ir 1 /TiO 2 (38%, at 87% conversion) and Mo 1 /TiO 2 (no activity) for the hydrogenation of 4-nitrostyrene (4-NS) to 4-vinylaniline (4-VA). Activation of the TiO 2 -supported bimetallic carbonyl cluster Ir 2 Mo 2 (CO) 10 (η 5 -C 5 H 5 ) 2 in an Ar atmosphere affords the DSAC Ir 1 Mo 1 /TiO 2 . Characterization of the dual single-atom structure confirms that it consists of well-dispersed Ir single atoms (Ir 1 ) and Mo single atoms (Mo 1 ) on TiO 2 . Density functional theory studies reveal that Ir 1 sites effect H 2 activation while Mo 1 sites are responsible for 4-NS adsorption, with synergistic cooperation between the two sets of single atoms contributing to the better catalytic performance for the hydrogenation of 4-NS. This work provides a deep understanding of synergistic effects in dual single-atom catalysis.