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

Abstract

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.