Iridium nanoparticles for oxygen evolution reaction on carbon and TiO2 supports from a Raman perspective

Ir-based electrocatalysts are crucial for oxygen evolution reaction (OER) in acidic media. Herein, the OER activity of Ir nanoparticles, produced by thermal annealing from iridium(III) bromide hydrate, is compared when deposited on carbon and titanium(IV) dioxide supports. Samples were investigated using Raman spectroscopy, but due to a small amount of Ir nanoparticles on supports only low intensity bands can appear. It is worth noting that other rare Raman literature (see Introduction) deals with bulk Ir-films/discs with a much larger amount of Ir in samples. Our results show weak bands of Ir-oxide at 548 (E-g) and 719 (B-2g + A(1g)) cm(-1) for the degraded states only. This indicates the degradation of Ir nanoparticles through oxidation on both investigated supports. Structural characteristics of supports and Ir nanoparticles were also investigated using X-ray diffraction and energy-dispersive X-ray spectroscopy. Electrochemical characterization shows that the OER activity of the Ir nanoparticles on carbon is significantly higher than that on TiO2.