Spatial and electronic effects synergistically enhanced electrocatalytic oxygen evolution using atomic iridium-anchored cobalt oxyhydroxide nanosheets

Abstract

Single-atom catalysts (SACs) based on noble metals play irreplaceable roles in the field of catalysis but unfortunately suffer from spatial constraints ranging from either lattice substitution, atomic dilution, or in-layer immobilization. Herein, this work was designed to overcome the limitation by locating discrete dangling coordinatively unsaturated [IrO5] motif atop γ-phase cobalt oxyhydroxide (γ-CoOOH) nanosheets to create a spatially novel catalyst (Ir1/CoOOHsur). For comparison, the lattice-doped catalyst (Ir1/CoOOHlat) was also synthesized via substituting Co in γ-CoOOH by Ir single atoms. The distinct location arrangements of Ir single atoms generated two different active sites that both weakened the adsorption of oxygenated intermediates relative to γ-CoOOH due to the upshifted O 2p-band center. Moreover, Ir1/CoOOHsur displayed a much weaker adsorption capability (closer to an ideal catalyst) than Ir1/CoOOHlat. Therefore, the spatial and electronic effects of discrete dangling [IrO5] motifs atop Ir1/CoOOHsur synergistically optimized the adsorption of oxygenated intermediates and thus gained the lowest energy barrier of the rate-determining step for oxygen evolution reaction. When used as the cathode catalyst in rechargeable zinc-air batteries, Ir1/CoOOHsur exhibited higher power density (101 mW cm−2) and cycling durability (800 h) than IrO2 (94 mW cm−2, 50 h). This study broadens noble metal-based SACs analogues and offers appealing opportunity to design target catalysts with the synergism of spatial and electronic effects for diverse catalytic applications.