Engineering Oxygen Vacancies in IrOX Clusters Supported on Metal-Organic Framework Derived Porous CeO2 for Enhanced Oxygen Evolution in Acidic Media

Developing highly active and stable electrocatalysts for the oxygen evolution reaction (OER) in acidic media for proton exchange membrane water electrolysis is urgent but still challenging. Herein, porous CeO2-supported IrOx clusters with different oxygen vacancy (Ov) concentrations are synthesized by the aid of N-rich and N-free isostructural Ce-based metal-organic frameworks (Ce-MOFs) as templates. Ov concentration in the derived IrOx clusters is effectively regulated by the presence of heteroatoms in MOFs. The optimized IrOx/CeO2 catalyst with high Ov (hov-IrOx/CeO2) exhibits a low overpotential of 251 mV at 10 mA cm-2, a higher turnover frequency (TOF) of 5400 h-1 and outstanding durability for at least 98 h of catalysis in 0.1 M HClO4, outperforming other analogues. Density functional theory calculations also show that the rich Ov in IrOx can weaken the binding energy between Ir and *O intermediates, which decreases the energy barriers for forming *OOH from *O in the rate-determining step. Additionally, the suppressed over-oxidation of Ir species as well as the corrosion resistance of the CeO2 support also contribute to the high stability.

Automated summary

In this study, porous CeO2-supported IrOx clusters with different oxygen vacancy concentrations were successfully synthesized using N-rich and N-free isostructural Ce-based metal-organic frameworks as templates. The optimized IrOx/CeO2 catalyst showed low overpotential, high turnover frequency, and outstanding durability, making it a promising candidate for proton exchange membrane water electrolysis.