Adsorption and Dissociation of CO on Gold Surfaces: Effect of Coverage and Adatom Clusters

Recent insights into the dynamic nature of catalyst surfaces under reactive conditions have motivated investigating heterogeneously catalyzed reactions through this lens. As an example system to revisit, CO interactions with gold have been a longstanding system of interest due to its structure sensitivity. In this work, we investigate coverage-dependent CO adsorption trends on terraces, steps, and kinks. Calculating differential binding energy and mean absolute displacement of the structures as a function of CO coverage, we propose a deformation quenching mechanism that partially determines saturation coverage. Extending this analysis to consider CO partial pressure, we show a phase change in CO step occupation, which we highlight as a viable explanation for previously reported temperature-programmed desorption and Fourier-transform infrared reflection-absorption spectroscopy measurements. In addition, we explore the reactivity of Au adclusters toward CO dissociation at the dilute coverage limit. We observe that Au-tetramers can accommodate a lower energy transition state than terraces and steps, but CO dissociation remains uncompetitive with CO desorption. This work shows how adopting a dynamic-surface lens can lead to additional insights which may be applied to other heterogeneously catalyzed systems.