**4. Conclusions**

We have investigated the effects of modifying the composition of LaCoO3 using DFT calculations. The vacancy formation energy, taken as a gauge of the catalytic activity, is reduced both by introducing Sr atoms at the La site and by doping with 3d atoms at the Co site. Only heavy 3d atoms are able to promote high density of vacancies, which is needed for NO reduction. Overall, Cu-doped and Ni-doped (La,Sr)CoO3 appear to be the best materials for preparation of catalysts suitable for three-way converters. It should, however, be pointed out that, due to the early nature of the transition state for the vacancy formation step in LSCO, the increased stability of oxygen vacancies obtained by doping is predicted to have a reduced influence on the catalytic properties when compared to that found for SrTiO3. Clearly, this work represents a first step towards a full understanding of the catalytic properties of these complex systems. More efforts, both on the theoretical and on the experimental side, is needed to extend and corroborate our conclusions.

**Author Contributions:** Conceptualization, A.V.; methodology, A.V.; software, A.V.; validation, A.V..; formal analysis, A.V.; investigation, A.V.; resources, A.V.; data curation, A.V.; writing—original draft preparation, A.V.; writing—review and editing, A.G.; visualization, A.V.; supervision, A.V.; project administration, A.G.; funding acquisition, A.G.

**Funding:** This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686086. This publication reflects only the author's view and the Commission is not responsible for any use that may be made of the information it contains.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


*Catalysts* **2019**, *9*, 312

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