Portal de Periódicos da CAPES

Ni Single Atom Catalysts for CO 2 Activation

2019; American Chemical Society; Volume: 141; Issue: 6 Linguagem: Inglês

10.1021/jacs.8b11729

1943-2984

Marie-Mathilde Millet, Gerardo Algara‐Siller, Sabine Wrabetz, Aliaksei Mazheika, Frank Girgsdies, Detre Teschner, Friedrich Seitz, Andrey Tarasov, Sergey V. Levchenko, Robert Schlögl, Elias Frei,

Catalysis and Oxidation Reactions

We report on the activation of CO2 on Ni single-atom catalysts. These catalysts were synthesized using a solid solution approach by controlled substitution of 1-10 atom % of Mg2+ by Ni2+ inside the MgO structure. The Ni atoms are preferentially located on the surface of the MgO and, as predicted by hybrid-functional calculations, favor low-coordinated sites. The isolated Ni atoms are active for CO2 conversion through the reverse water-gas shift (rWGS) but are unable to conduct its further hydrogenation to CH4 (or MeOH), for which Ni clusters are needed. The CO formation rates correlate linearly with the concentration of Ni on the surface evidenced by XPS and microcalorimetry. The calculations show that the substitution of Mg atoms by Ni atoms on the surface of the oxide structure reduces the strength of the CO2 binding at low-coordinated sites and also promotes H2 dissociation. Astonishingly, the single-atom catalysts stayed stable over 100 h on stream, after which no clusters or particle formation could be detected. Upon catalysis, a surface carbonate adsorbate-layer was formed, of which the decompositions appear to be directly linked to the aggregation of Ni. This study on atomically dispersed Ni species brings new fundamental understanding of Ni active sites for reactions involving CO2 and clearly evidence the limits of single-atom catalysis for complex reactions.