For the last few decades, the development of non-noble metal or metal-free catalysts for hydrogen economy has been a field of growing interest. Among others, Oxygen reduction reaction (ORR), water splitting and hydrogen evolving reaction (HER) are crucial reactions that must be well controlled to optimize the efficiency of fuel cells. Some metalloprotein is designed in such a way they can protect a biological process from the potentially harmful effects of oxygen and other reactive oxygen-containing molecules such as H2O2. These systems include peroxidases, catalases, and superoxide dismutases. The research is guided by a desire to understand the key structural and functional features of both heme and nonheme enzymes that utilize dioxygen for a wide variety of oxidation reactions. With this goal in mind, the approach is to incorporate these features into synthetic complexes that model enzyme active sites and to examine analogous reactivity at a mechanistic level.