Synergy of Single-Atom Ni₁ and Ru₁ Sites on CeO₂ for Dry Reforming of CH₄

Abstract

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 (Ni1 and Ru1) anchored on the surface of a CeO2 nanorod, Ce0.95Ni0.025Ru0.025O2. The surface of this catalyst, Ce0.95Ni0.025Ru0.025O2, consists of two sets of single-atom sites which are highly active for reforming CH4 using CO2 with a turnover rate of producing 73.6 H2 molecules on each site per second at 560 °C. Selectivity for producing H2 at this temperature is 98.5%. The single-atom sites Ni1 and Ru1 anchored on the CeO2 surface of Ce0.95Ni0.025Ru0.025O2 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 H2 and CO on Ce0.95Ni0.025Ru0.025O2 in contrast to Ce0.95Ni0.05O2 with only Ni1 single-atom sites and Ce0.95Ru0.05O2 with only Ru1 single-atom sites. Computational studies suggest a molecular mechanism for the observed synergy effects, which originate at (1) the different roles of Ni1 and Ru1 sites in terms of activations of CH4 to form CO on a Ni1 site and dissociation of CO2 to CO on a Ru1 site, respectively and (2) the sequential role in terms of first forming H atoms through activation of CH4 on a Ni1 site and then coupling of H atoms to form H2 on a Ru1 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.

Atomically dispersed nickel as coke-resistant active sites for methane dry reforming

“…In light of the thermodynamic stability of CH 3 to subsequent C–H cleavage over our catalysts, the appearance of CO as a major product in our catalytic system appears paradoxical. However, a recent report of DRM over Ni 4 clusters (which also show good carbon deposition resistance 52 ) identified the oxidation of CH 3 to CH 3 O as an alternative route to CO following initial methane activation, as also proposed for Ni 1 –Ru 1 /CeO 2 42 . We therefore considered this alternative route for transforming reactively formed CH 3 to CO without carbon deposition (Fig.…”

“…Recent elegant work by Tang et al 42 reported a synergy between single-atom Ru 1 and Ni 1 sites resulting in very high activity for DRM even at 600 °C. Significant performance benefits accrued for our catalytic system under identical reaction conditions, even for loadings that do not exclusively give rise to single atoms: the 2 wt% Ni 1 /HAP-Ce catalyst delivered similar activity and superior stability (Supplementary Fig.…”

Designing Atomic Active Centers for Hydrogen Evolution Electrocatalysts

“…Thea tomic active centers mentioned above possess only one type of single atoms.Iftwo or more types of single-metal atoms are introduced, an enhanced HER performance may be expected. [195][196][197][198] In two-metal active centers,o ne kind of metal atom may modify the electronic structure of the other to enhance the HER activity. [199] We [200] synthesized uniformly dispersed Cu-Pt sites on Pd nanorings (NRs;F igure 9a,b) by at wo-step wet chemical method.…”

Single‐Atom Catalysts in Catalytic Biomedicine

“…Furthermore, the current research focusing on biomedical applications of SACs mainly concentrates on cancer treatment, wound disinfection, biosensing, and oxidative‐stress cytoprotection, while other biomedical applications including diagnosis, multimodal imaging, inflammation alleviation as well as Alzheimer's disease, Parkinson's disease, and diabetes treatment are rarely studied. In addition, although numerous SACs have been successfully fabricated, including diverse single metal atoms (Au, Co, Fe, Ir, Ru, Pt, Pd, etc.) on various supports such as N‐doped carbon, metal oxides, and layered double hydroxides, only Fe‐, Au‐, Zn‐, and Cu‐based SACs, especially M‐N‐C nanostructures, have been demonstrated their potential in biomedical applications.…”