Synergy of Single-Atom Ni 1 and Ru 1 Sites on CeO 2 for Dry Reforming of CH 4

Heterogeneous catalysis performs on specific sites of a catalyst surface even if specific sites of many catalysts during catalysis could not be identified readily. Design of a catalyst by managing catalytic sites on an atomic scale is significant for tuning catalytic performance and offering high activity and selectivity at a relatively low temperature. Here, we report a synergy effect of two sets of single-atom sites (Ni 1 and Ru 1 ) anchored on the surface of a CeO 2 nanorod, Ce 0.95 Ni 0.025 Ru 0.025 O 2 . The surface of this catalyst, Ce 0.95 Ni 0.025 Ru 0.025 O 2, consists of two sets of single-atom sites which are highly active for reforming CH 4 using CO 2 with a turnover rate of producing 73.6 H 2 molecules on each site per second at 560 °C. Selectivity for producing H 2 at this temperature is 98.5%. The single-atom sites Ni 1 and Ru 1 anchored on the CeO 2 surface of Ce 0.95 Ni 0.025 Ru 0.025 O 2 remain singly dispersed and in a cationic state during catalysis up to 600 °C. The two sets of single-atom sites play a synergistic role, evidenced by lower apparent activation barrier and higher turnover rate for production of H 2 and CO on Ce 0.95 Ni 0.025 Ru 0.025 O 2 in contrast to Ce 0.95 Ni 0.05 O 2 with only Ni 1 single-atom sites and Ce 0.95 Ru 0.05 O 2 with only Ru 1 single-atom sites. Computational studies suggest a molecular mechanism for the observed synergy effects, which originate at (1) the different roles of Ni 1 and Ru 1 sites in terms of activations of CH 4 to form CO on a Ni 1 site and dissociation of CO 2 to CO on a Ru 1 site, respectively and (2) the sequential role in terms of first forming H atoms through activation of CH 4 on a Ni 1 site and then coupling of H atoms to form H 2 on a Ru 1 site. These synergistic effects of the two sets of single-atom sites on the same surface demonstrated a new method for designing a catalyst with high activity and selectivity at a relatively low temperature.