*Recent Progress on Metal Hydride and High Entropy Materials as Emerging Electrocatalysts… DOI: http://dx.doi.org/10.5772/intechopen.113105*

where O2 is firstly reduced directly to H2O2 as intermediates and later to H2O [24]. The former reaction is ideally applicable in fuel cells and the latter reaction produces H2O2 which is good for the green synthesis process, for the treatment of wastewater and disinfection [25]. The good ORR performance should obey the Sabier principle where the adsorption strength of these intermediates (OOH\*, OH\* and O\*) should neither be too weak nor too strong to bind the active site. In theory, according to the volcano plot the different electrocatalysts are demonstrated based on their catalytical activity performance. The use of the model assists in knowing why Pt and Pd with their alloys are better cathode electrocatalysts over other metals before performing the experimental analysis [26]. Then from now on, Pt and Pd-based electrocatalysts have greatly been investigated as ORR catalysts due to their electronic structure for O (from dissociation of O2) and OH binding energies [27].
