Adsorption study of CO and O2 on Au5-x-yAgxCuy [x, y = 1, 3] trimetallic nanoclusters

In present study, we focus on adsorption of CO and O₂ gases over different trimetallic nanocluster. Among all trimetallic nanoclusters, copper occupied four coordinated sites and found to be nearly planer. The adsorption of carbon monoxide (CO) at these four coordinated sites drastically changes the structure of all the trimetallic nanoclusters. The adsorption trend of CO followed by all trimetallic nanoclusters is copper, gold and silver respectively. The anomalous behaviour arises due to the relativistic effect in the case of gold. The relativistic effect destabilizes the d-orbital and s-orbital. The destabilized d-orbital enhances the pi-back bonding. Unlike CO, the O₂ adsorption at four coordinated Cu-sites does not bring as drastic changes in the geometry of the nanocluster as it in the case of CO adsorption at 4-coordinated Cu-site. In contrast, CO adsorbs on these nanoclusters as one atom on top of another (μ₁η¹-atop mode), whereas O₂ exhibits three types of bonding-bridging mode, atop mode (-μ₂η² or μ₂η¹ - bridging mode or μ₁η¹-atop mode).