**4. Conclusions**

The effects of partial substitution of La by Sr and of Ni by Ru or Rh in the LaNiO3 structure were investigated in an attempt to systematically study the effects of the nature and composition of the A- and B-sites of the perovskite-derived catalysts for the propane steam reforming (PSR) reaction. The physicochemical characteristics of the as-prepared LaNiO3 (LN), La0.8Sr0.2NiO3 (LSN), and noble metal-substituted LNM*x* and LSNM*x* perovskites (M = Ru or Rh; *x* = 0.01 or 0.1) as well as the used catalysts obtained following exposure to reaction conditions were studied by employing the BET method and the XRD technique. Results obtained can be summarized as follows:


**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/nano11081931/s1. Figure S1. SEM image (A), EDS mapping results showing the distribution of (B) La, (C) Sr, (D) Ni, (E) Rh and (F) La (green spots), Ni (blue spots) and Rh (red spots) elements and corresponding EDS spectrum (G) over the as-prepared LSNRh0.1 perovskite sample; Figure S2. SEM image (A), EDS mapping results showing the distribution of (B) Carbon, (C) La, (D) Sr, (E) Ni and (F) Rh elements and corresponding EDS spectrum (G) over the "used" LSNRh0.1 perovskite sample; Table S1: Cell parameters of the crystalline phases detected by XRD for the as-prepared perovskite samples and the derived (used) catalysts.

**Author Contributions:** T.R. and D.I.K. conceived and designed the experiments; T.R., A.V. and G.V. performed the experiments; T.R., G.B. and D.I.K. analyzed the results and wrote the paper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH-CREATE-INNOVATE (project code: T1EDK-02442).

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
