In Situ/Operando Capturing Unusual Ir6+ Facilitating Ultrafast Electrocatalytic Water Oxidation

Identifying real active sites and understanding the mechanism of oxygen evolution reaction (OER) are still a big challenge today for developing efficient electrochemical catalysts in renewable energy technologies. Here, using a combined in situ/operando experiments and theory, the catalytic mechanism of the ordered OER active Co and Ir ions in Sr2CoIrO6-delta is studied, which exhibits an unprecedented low overpotential 210 mV to achieve 10 mA cm(-2), ranking the highest performance among perovskite-based solid-state catalysts. Operando X-ray absorption spectroscopies as a function of applied voltage indicates that Ir4+ ion is gradually converted into extremely high-valence Ir5+/6+, while the part of Co3+ ion is transferred into Co4+ under OER process. Density functional theory calculations explicitly reveal the order Co-O-Ir network as an origin of ultrahigh OER activity. The work opens a promising path to overcome the sluggish kinetics of OER bottleneck for water splitting via proper arrangements of the multi-active sites in catalyst.

Automated summary

This study investigates the catalytic mechanism of ordered OER active Co and Ir ions in Sr2CoIrO6-δ, achieving unprecedented low overpotential and high catalytic performance. Experimental results show gradual conversion of Ir4+ ions to Ir5+/6+ and part of Co3+ ions to Co4+, while density functional theory calculations reveal the ordered Co-O-Ir network as the origin of ultrahigh OER activity. These findings open a promising pathway to overcome the sluggish kinetics of OER bottleneck for water splitting by proper arrangements of multi-active sites in the catalyst.