Heterogeneous catalysis performs on specific sites of catalyst surface even if the specific sites of a catalyst during catalysis could not be identified readily. Design of a catalyst through managing catalytic sites at an atomic scale is significant for tuning catalytic performance and offering high activity and selectivity at a relatively low temperature. Here we report synergy effects of two sets of single-atom sites (Ni1 and Ru1) anchored on surface of a CeO2 nanorod, Ni0.025Ru0.025Ce0.95O2. Surface of this catalyst, Ni0.025Ru0.025Ce0.95O2 consists of two sets of single-atom sites, which are highly active for reforming CH4 with CO2 with a turn-over rate of producing 73.6 H2 molecules on each site per second at 560oC. Selectivity for producing H2 is 98.5% at this temperature. The single-atom sites, Ni1 and Ru1 anchored on CeO2 surface of Ni0.05Ru0.05Ce0.95O2 remain single dispersion and cationic state during catalysis up to 600oC. The two sets of single-atom sites play a synergy role, evidenced by lower apparent activation barrier and higher turn-over rate for production of H2 and CO on Ni0.025Ru0.025Ce0.95O2 in contrast to Ni0.05Ce0.95O2 with only Ni1 single-atom sites and Ni0.05Ce0.95O2 with only Ru1 single-atom sites. Computational studies uncovered molecular mechanism of the observed synergy effects which are originated at (1) the different role of Ni1 and Ru1 in terms of activations of CH4 to form CO on Ni1 site and dissociation of CO2 to CO on Ru1 site, respectively, and at (2) the sequential role in terms of first forming H atoms through activation of CH4 on Ni1 site and then coupling H atoms to form H2 on Ru1 site. The synergy effects of two sets of single-atom sites on the same surface demonstrated a new avenue for designing a catalyst with high activity and selectivity at a relatively low temperature.

Synergy effect of two sets of single-atom sites (Ni1 and Ru1) on catalyst surface for reforming CH4

2019 Spring National Meeting

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