First, we start by comparing the efficiency of PGM and non-PGM catalysts. As they have significant differences in their electronic structure, there would be a range of differences in their efficiency. PGM catalysts such as platinum, palladium, and ruthenium demonstrate exceptional catalytic activity, especially in electrochemical reactions such as ORR. Such high catalytic activity of PGM catalysts is attributed to their unique electronic structure, primarily characterized by the d-band structure . During the ORR process, the d-orbitals will interact with oxygen electrons, facilitating subsequent electron transfer. The localized d-band center will be activated as oxygen intermediates react on the catalyst's active sites, dominating the bonding strength between the absorption species and the active sites, thereby enhancing the ORR activity. Most metal catalysts possess a d-band structure that gives them a d-state energy. A higher d-state energy for metal signifies greater catalytic reactivity, therefore explaining why PGM catalysts emerge as a more efficient catalyst for ORR . For instance, the half-wave potential (E 1/2 ) of a Pt/C catalyst during ORR under acidic conditions shows a result of 0.88V (vs.RHE) in comparison to Fe-based Single Atom Catalysts (SACs) Fe-N-C showing an E 1/2 of 0.784V in acidic electrolyte, the significant disparity highlighting the better performance of Pt/C catalysts, indicating the better in performance for PGM catalysts compared to basic non-PGM catalysts . Conversely, one of the key differences faced by non-noble metal catalysts is their lower catalytic activity compared to PGM catalysts. Because they do not exhibit the same level of catalytic activity, they could potentially impact the overall fuel cell efficiency. It has been proven that non-noble metal catalysts without specific engineering will be hard to exceed the high catalytic activity of PGM catalysts such as Pt/C catalysts. Even with stability and durability concerns, non-PGM catalysts will be disadvantaged compared to PGM catalysts due to their difference in electronic structure.