**4. Conclusions**

ZIF-67 derived nano-porous carbon that is further doped with MnO2 particles offers a potential material to be used as ORR catalyst in fuel cells, and the material shows good ORR performance. Onset potentials, peak potential and peak current densities were calculated using current vs. voltage plots obtained through cyclic voltammetry. The modified material ZCNT-M showed better performance as compared to ZCNT, as observed through cyclic voltammetry and EIS. The material showed a performance enhancement up to a certain level of oxygen purging, as compared to its performance with dissolved oxygen in the electrolyte. In addition, electrochemical stability was tested by using chronoamperometry, showing a sudden decrease in current and stable performance up to 3600s. Ultimately, it can be concluded from this work that the good catalytic ORR activity of ZIF-67 derived CNTs/MnO2 (ZCNT-M) is due to the incorporation of MnO2 not only enhancing the surface area, but also the conductivity of prepared catalysts to a significant level.

**Author Contributions:** Conceptualization, U.S.; Data curation, U.S., T.N., S.H., H.E. and N.Z.; Formal analysis, N.I., H.E. and S.A.; Investigation, T.N.; Methodology, U.S., N.I., S.H., N.Z. and S.A.; Supervision, T.N. and S.A.; Writing–original draft, U.S., S.H., H.E. and N.Z.; Writing–review & editing, N.I. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** Research work was done at laboratories at USPCAS-E, NUST and the Department of Physical Chemistry, Quaid-e-Azam University, Islamabad, Pakistan.

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