Site-specific stabilizing effect of single atoms on spinel oxides for acidic oxygen evolution

Developing efficient and economical non-precious metal electrocatalysts for acidic oxygen evolution reaction (OER) is crucial for proton exchange membrane water electrolyzers (PEMWE). Spinel oxides are considered promising non-precious acidic OER catalysts due to their excellent activities. However, the structure dissolution of spinel oxides in acidic conditions severely limits their applications in PEMWE. Introducing acid-resistant heteroatoms into spinel oxides is an available strategy to enhance their stability. Herein, by anchoring Ir single atoms at different sites of spinel oxide Co 3 O 4 , we demonstrated that the stabilizing effect strongly depends on the single-atom anchoring site. Electrochemical measurements and in situ spectroscopic characterization revealed that the Ir single atoms anchored at lattice sites significantly enhanced the stability of Co 3 O 4 during acidic OER in comparison with ones at three-fold hollow sites. The long-term durability test showed that the Ir single atoms at lattice sites stabilized Co 3 O 4 during a 200 ​h continuous operation at a current density of 10 ​mA ​cm − 2 . Moreover, the resultant PEMWE device fabricated by the catalyst achieved a stability time of about 60 ​h at a current density of 1 ​A ​cm − 2 . Mechanistic studies revealed that Ir single atoms at lattice sites enhanced the covalency between Co and O atoms, thereby suppressing their migration and improving the stability of spinel oxides. The discovery of the site-specific stabilizing effect of single atoms provides essential guidance for the rational design of highly stable electrocatalysts for PEMWE. • Ir single atoms have been anchored at the three-fold hollow sites and lattice sites of Co 3 O 4 , respectively. • Ir single atoms at lattice sites enhanced the stability of Co 3 O 4 compared with the ones at three-fold hollow sites. • Mechanistic studies revealed lattice sites-anchored Ir single atoms enhanced the Co-O covalency to enhance the stability.