**4. Conclusions**

The results of the present study show that the catalytic activity of Ni and the product distribution for the propane steam reforming reaction depend strongly on the nature of the support. The specific reaction rate measured for Ni/ZrO2 catalyst was found to be more than one order of magnitude higher compared to that measured for Ni/TiO2. The intermediate production of CH4 is strongly influenced by the type of metal oxide used as support following the same trend with that of catalytic activity. DRIFTS studies provided evidences that the most active Ni/ZrO2 catalyst is able to convert the intermediate produced CH*x* species to CH4 and/or formate species and, subsequently, to carbon oxides and H2. In contrast, CH*x* species seem to be less reactive when Ni is dispersed on TiO2, thus resulting in a lower reaction rate. In addition to the high activity of Ni/ZrO2 catalyst, it was also found to be stable for more than 30 h on stream and therefore, is a promising candidate for the production of H2 for fuel cell applications.

**Author Contributions:** Conceptualization, P.P.; methodology, P.P.; investigation, A.K., A.P. and P.P.; data curation, A.K., A.P. and P.P.; writing—original draft preparation, P.P.; writing—review and editing, P.P.; visualization, P.P.; supervision, P.P.; project administration, P.P.; funding acquisition, P.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research has been 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).

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

**Informed Consent Statement:** Not applicable.

**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.
