Energy conversion is perhaps one of the most serious challenges of current society. The adverse effect of fossil fuels on the environment and their limited reserves, make them an unsustainable energy source in the long term for a constantly growing population. Developing green and efficient energy conversion technologies is crucial to achieve carbon neutrality targets and support a global economic growth. Toward this end, proton exchange membrane fuel cells (PEMFCs) have attracted considerable attention due to their ability to operate at low-temperature, high energy conversion efficiency, excellent durability, and sustainable regeneration. PEMFCs are electrochemical devices that convert the chemical energy of a fuel, hydrogen (H2), directly into electricity without emission of pollutants, i.e., ideally water is the only byproduct. The continuous fuel supply renders PEMFC as the ideal power source for portable electric vehicles and stationary power plants for critical infrastructures.