Bending the ORR Scaling Relations on Zirconium Oxynitride for Enhanced Oxygen Electrocatalysis

Technologies like polymer electrolyte membrane fuel cells play an important role in environmentally friendly energy conversion. Essential for their commercialization is the development of cheap and efficient electrocatalyst for the oxygen reduction reaction (ORR). Non-platinum group metal (PGM) based catalysts has exhibited favourable activity in acidic electrolytes. In this study, we computationally explore the catalytic sites on the (111) surface of hydrated zirconium oxynitride using periodic DFT calculations. The thermodynamically limiting step is determined to be the O-2 activation step, (O-2 -> OOH*) for the majority of the sites, hence strengthening the OOH* intermediate binding will improve ORR activity. The calculations also reveal that the determined scaling relation for G(OH)-G(OOH) (Delta G(OOH) = 0:78 Delta G(OH)+3.52 eV) is comparable to the standard ORR scaling relation (Delta G(OOH) = Delta G(OH)+3.2 eV) however G(O*)-G(OH) scaling (Delta G(O*) = 1.04 Delta G(OH)+2.16 eV) deviates dramatically from the typical ORR scaling relation (Delta G(O*) = 2 Delta G(OH)).