Atomically dispersed silver atoms incorporated in spinel cobalt oxide (Co₃O₄) for boosting oxygen evolution reaction

Incorporating noble metal single atoms into lattice of spinel cobalt oxide (Co₃O₄) is an attractive way to fabricate oxygen evolution reaction (OER) electrocatalysts because of the high activity and economic benefit. The commonly used high valence noble metal dopants such as ruthenium, iridium and rhodium tend to supersede Co³⁺ at octahedral site of Co₃O₄ and result in great activity, the origins of admirable activity were also wildly investigated. However, bare explorations on doping noble metal single atom into tetrahedral site of Co₃O₄ to construct OER catalyst have been reported, corresponding catalytic activity and mechanism remain mystery. Here, a promising structure that tetrahedrally substituent Ag single atom embedded in Co₃O₄ nanoparticles on the surface of carbon nanotube (Ag-Co₃O₄/CNT) was presented, and its performance in OER was probed. The high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XAS) demonstrate the successful embeddedness of atomical Ag atom in Co₃O₄ lattice, the resultant electronic interaction is conducive to promote charge transfer for OER. Theoretical calculations further disclose that atomical Ag dopant prefers to replace tetrahedral Co²⁺ rather than octahedral Co³⁺. The substitution Ag acts as the active site through Ag-Co bridge and facilitates the desorption process, which improves the turnover frequency (TOF) and boosts the intrinsic activity of Ag-Co₃O₄/CNT. Benefiting from the essentials above, Ag-Co₃O₄/CNT displays remarkable activity (236 mV@10 mA cm^-2) and robust stability for alkaline OER. This finding offers a potential direction for the design of noble metal single atom involved Co₃O₄ based OER electrocatalysts.