| Abstract |
The growth of NiCo particles at low coverages over reducible CeO2(111) thin films producing a triple interface between Ni–Co–Ce was investigated by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), which was compared to that of monometallic Ni and Co particles. XPS data show that deposition of either Ni or Co on CeO2 at 300 K causes a partial reduction of Ce4+ cations to Ce3+ ions. At 0.3 monolayer (ML), XPS detects Co2+ on CeO2. However, both Ni0 and Ni2+ are present as major species at 300 K and annealing causes a significant increase of Ni2+ in Ni particles. Deposition of 0.3 ML Co over 0.3 ML Ni on CeO2 at 300 K induces reduction of Ni2+ to metallic Ni and Ni0 was found as predominant species. Unlike for Co/CeO2, metallic Co was also present over the Co–Ni/CeO2 surface in addition to Co2+. This behavior indicates the formation of NiCo bimetallic particles with the possibility of Co diffusion to the interface of Ni/ceria. With heating, the intermixing of Ni and Co atoms in bimetallic particles on CeO2 was facilitated. Furthermore, oxidation of both metals and ceria occurred as a result of the diffusion of lattice oxygen from the bulk of ceria to the surface. A slight increase in Ni2+ was observed after heating Co–Ni/CeO2 to 500 K or higher. Co became Co2+ with heating to 800 K. Our STM results confirm the formation of NiCo bimetallic particles on CeO2 at 300 K and further suggest that the addition of Co can help inhibit the sintering of Ni particles at higher temperatures. Bimetallic particles were also obtained by depositing Ni over existing Co particles on CeO2. However, our XPS data demonstrate that the deposition order of Co and Ni plays a role in the chemical state of these two metals in bimetallic particles, likely attributed to the difference in their compositions at the bimetallic particle surface as well as the metal–support interface. |
| Authors |
Nishan Paudyal   , Tasnim Ara , Linze Du Hill , Sanjaya D. Senanayake , Jing Zhou
|
| Journal Info |
American Chemical Society | The Journal of Physical Chemistry C , vol: 128
, iss: 39
, pages: 16754 - 16765
|
| Publication Date |
9/24/2024 |
| ISSN |
1932-7447 |
Type |
article |
| Open Access |
closed
|
| DOI |
https://doi.org/10.1021/acs.jpcc.4c04802 |
| Keywords |
Bimetallic strip (Score: 0.86186075) , Component (thermodynamics) (Score: 0.66388816) , Interface (matter) (Score: 0.6040356) , Chemical Stability (Score: 0.46511605) , Triple junction (Score: 0.4371849)
|
