ABSTRACT
Currently our society heavily relies on fossil fuels as energy sources for electricity and transportation, causing many problems, including energy insecurity, air pollution, and enormous CO2 emission. Because of the gradual depletion of fossil fuels and intolerance of the environment, much attention has been paid to sustainable and renewable energy. Hydrogen is an excellent energy-storage medium for sustainable and renewable energy systems.1-3 The advantages of hydrogen as an energy carrier include (1) high efficiency, reversible conversion between hydrogen and electricity; (2) good energy density of
compressed hydrogen storage; and (3) scalability of hydrogen technologies for grid-scale applications.4 Switching fossil fuel economy to hydrogen economy could provide health, environmental, climate, and economic benefits and could reduce reliance on diminishing oil supplies.5
