Microkinetic Modelling of Electrochemical Oxygen Evolution Reaction on Ir(111)@N-Graphene Surface.

We have explored the thermodynamics and microkinetic aspects of oxygen evolution catalysis on low loading of Ir(111) on nitrogen-doped graphene at constant potential. The electronic modification induced by N-doping is the reason for the reduced overpotential of OER. The N-induced defect in the charge density is observed with increasing charge-depleted region around the Ir atoms. The lattice contraction shifts the d-band center away from the Fermi level, which increases the barrier for OH* and O* formation on Ir(111) supported on NGr (Ir(111)@NGr). Thus, highly endothermic O* formation reduces the OOH* formation, which is the potential determining step. For comparison, all electronic and binding energy calculations were also performed against Ir NP supported on Gr (Ir(111)@Gr). The stepwise potential-dependent activation barrier ( ) was obtained using the charge extrapolation method. The third step remains the RDS in all ranges of water oxidation potentials. The potential dependent is further applied to the Eyring rate equation to obtain the current density ( ) and correlation between and pH dependence, i. e., OH concentration. The microkinetic progression leads to a Tafel slope value of 30 mV dec at pH=14.0, requiring .