This thesis explores advanced catalysts for energy conversion, focusing on two key projects. The first project explores doped PtRu catalysts to improve CO tolerance in proton exchange membrane (PEM) fuel cells. Using density functional theory (DFT), Pd- and Rh-doped PtRu catalysts were identified as promising due to their resistance to CO poisoning. These findings suggest the potential to enhance PEM fuel cell anode durability and reduce fuel purification requirements, though experimental validation is needed. The second project focuses on nitrogen-doped carbon catalysts for electrochemical CO2 reduction (CO2RR). Jialang Li’s thesis ([86]) demonstrated that nitrogen doping lowers the energy barrier for CO2 reduction, enhancing catalytic activity. In my study, both Vulcan XC 72-R and CIC-85 were investigated. Untreated carbon black (Vulcan XC 72-R) and CIC-85 were found to be inactive for CO2RR. Acid treatment increased the surface oxygen content but did not significantly enhance catalytic activity. However, when acid-treated Vulcan car- bon or CIC-85 was subjected to high-temperature ammonia treatment, substantial nitrogen doping was achieved, as confirmed by advanced surface characterization techniques. My results show that increased oxygen content from acid treatment facilitated greater nitrogen incorporation during ammonia doping, significantly improving CO2RR activity and selectivity. These findings highlight the role of oxygen content in enabling higher nitrogen doping and improving performance for CO2 reduction. These results contribute to both theoretical and experimental advancements in the development of catalysts for sustainable energy applications.