**4. Conclusions**

This study investigated the activity and stability performance of SrNiO3 and CeNiO3 perovskites for DRM. The analysis results of CeNiO3 prior to the reaction revealed welldispersed nickel nanoparticles over the catalyst's surface, enhanced number of reducible

species, and higher specific surface areas and pore volumes, which remained key factors in influencing both catalytic activity and durability. The CeNiO3 perovskite demonstrated higher CH4 and CO2 conversions as compared to SrNiO3 but both perovskites deactivated over time. Lower activity in the case of SrNiO3 reveals the fact that nickel active sites are covered with strontium carbonates, which is in agreemen<sup>t</sup> with previously reported results. The analyses of the perovskites after reaction assisted in locating the cause of deactivation. Though all perovskites showed significant sintering, it was not considered to be the main cause of deactivation as SrNiO3 showed more deactivation despite a similar extent of sintering. Hence, carbon deposition, as evidenced by the TEM and TPO images of spent perovskites, was the main deactivation factor. The investigation of recyclability, reactivation of the developed catalyst system, and the role of strontium combined with Ce-based perovskites are planned for future work.

**Author Contributions:** N.A., F.A., and M.A. synthesized the catalysts, carried out all the experiments and characterization tests, and wrote the manuscript. R.W., B.A., and S.M. prepared the catalyst and contributed to proofreading of the manuscript. N.A. and F.A. contributed to the analysis of the data and the writing and review of the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by King Saud University under NPST project (14-PET851-02).

**Institutional Review Board Statement:** Not Applicable.

**Informed Consent Statement:** Not Applicable.

**Data Availability Statement:** Not Applicable.

**Acknowledgments:** The authors would like to extend their sincere appreciation to the King Saud University for its funding to this NPST project (14-PET851-02).

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