Site-specific stabilizing effect of single atoms on spinel oxides for acidic oxygen evolution
Zhirong Zhang, Peiyu Ma, Chuanyi Jia, Wenting Gao, Mingkai Liu, Kwun Nam Hui, Ming J. Zuo, Shiming Zhou, Jie Zeng
Abstract
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.