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

Abstract

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 IrO x 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 IrO x clusters is effectively regulated by the presence of heteroatoms in MOFs. The optimized IrO x /CeO2 catalyst with high Ov (hov-IrO x /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 IrO x 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.

Perspectives on the development of highly active, stable, and cost‐effective OER electrocatalysts in acid

“…Recently, Li et al further developed porous CeO 2 ‐supported IrO x with high V O which exhibited an excellent acidic OER performance (251 mV at 10 mA cm −2 for 90 h) (Figure 10D). 135 By modifying the CeO 2 support, the authors maximized the ECSA as indirectly confirmed by electrochemical double‐layer capacitance comparison ( C dl ) (Figure 10E).…”

“…(E) Comparison of calculated C dl values of supported and nonsupported IrO 2 . Reproduced with permission 135 . Copyright 2023 American Chemical Society.…”

An IrRuOx catalyst supported by oxygen-vacant Ta oxide for the oxygen evolution reaction and proton exchange membrane water electrolysis

“…Since Ta 2 O 5 was fully covered by IrRuO x and underwent air treatment, the remaining oxygen vacancies also originated from IrRuO x clusters due to their high surface-to-volume ratios. 35…”

“…Since Ta 2 O 5 was fully covered by IrRuO x and underwent air treatment, the remaining oxygen vacancies also originated from IrRuO x clusters due to their high surface-to-volume ratios. 35 The surface compositions of the studied samples were examined by XPS, and Ta, Ir, Ru, and O were all detected in the full spectrum of IrRuO x /Ta 2 O 5 (Fig. 3D).…”

Investigating the Influence of Amorphous/Crystalline Interfaces on the Stability of IrO2 for the Oxygen Evolution Reaction in Acidic Electrolyte

“…The O 1s spectrum of IrO 2 -300 °C in Figure 9a consists of three contributions at 529.9, 531.7 and 533.2 eV, which are attributed to lattice oxygen (O), Ir-OH (possibly formed at vacancy sites) and absorbed water (H 2 O), respectively. [82][83] The contents of each of these components is listed in Table S3. The most significant change is that the Ir-OH percentage in the sample decreased after annealing the sample from RT to 300 °C.…”