A crucial element in achieving this paradigm shift is the use of electrochemistry to convert electrical energy into hydrogen and to convert hydrogen back into energy without direct combustion in air. Proton exchange membrane fuel cell (PEMFC) is a promising electrochemical system for efficiently converting hydrogen into electricity, both in stationary applications such as homes and buildings, and in mobility applications such as passenger-owned vehicles and heavy-duty vehicles. Intensive research and development efforts have led to remarkable improvements in efficiency and durability. However, for wider adoption, further enhancements in the activity and durability of cathode catalysts are necessary. According to the New Energy and Industrial Technology Development Organization (NEDO) in Japan, it is estimated that by 2035, catalytic activity must increase more than ninefold, from 500 A g -1 to 4630 A g -1 . In addition, it is necessary to suppress catalyst dissolution, which leads to degradation through Ostwald ripening during operation. Cathode catalyst needs to activate the oxygen reduction reaction (ORR):