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

Abstract

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 (DG OOH ¼ 0:78DG OH þ3.52 eV) is comparable to the standard ORR scaling relation (DG OOH ¼ DG OH þ3.2 eV) however G O* -G OH scaling (DG O* ¼ 1:04DG OH þ2.16 eV) deviates dramatically from the typical ORR scaling relation (DG O* ¼ 2DG OH ).

Understanding the Electronic and Structural Effects in ORR Intermediate Binding on Anion‐Substituted Zirconia Surfaces

“…[30] In our previous work we have explored the possibility of enhanced ORR activity due to bending of ORR scaling relations. [31] We concluded that the G O -G OH scaling relation for ORR on Zr 2 ON 2 catalyst indeed shows deviation from the standard scaling relation, however, there was no indication that it necessarily results in enhanced electrocatalysis. Several electronic descriptors failed to capture the complexity of the Zr 2 ON 2 catalyst surface that arises from presence of two different anions i. e. oxygen and nitrogen in the anionic layers.…”