However, Pt alloys have limitations. The secondary elements currently introduced into Pt are unstable in acidic electrolytes. They dissolve during operation, leading to a decrease in catalytic activity due to dealloying. Furthermore, the dissolved elements not only reduce activity but also bind to sulfonic acid groups in the proton exchange membrane, lowering its proton conductivity. Due to these adverse effects, even though introducing more secondary elements could enhance catalytic activity, it becomes necessary to limit the amount to ensure durability. Despite extensive research to balance activity and durability, very few materials have been found that escape this trade-off relationship.