Ab Initio Investigation of CO₂ Adsorption on 13-Atom 4d Clusters

Abstract

In this work, we report an ab initio investigation based on density functional theory calculations within van der Waals D3 corrections to investigate the adsorption properties and activation of CO2 on transition-metal (TM) 13-atom clusters (TM = Ru, Rh, Pd, Ag), which is a key step for the development of subnano catalysts for the conversion of CO2 to high-value products. From our analyses, which include calculations of several properties and the Spearman correlation analysis, we found that CO2 adopts two distinct structures on the selected TM13 clusters, namely, a bent CO2 configuration in which the OCO angle is about 125 to 150° (chemisorption), which is the lowest energy CO2/TM13 configuration for TM = Ru, Rh, Pd. As in the gas phase, the linear CO2 structure yields the lowest energy for CO2/Ag13 and several higher energy configurations for TM = Ru, Rh, Pd. The bent CO2 (activated) is driven by a chemisorption CO2–TM13 interaction due to the charge transfer from the TM13 clusters toward CO2, while a weak physisorption interaction is obtained for the linear CO2 on the TM13 clusters. Thus, the CO2 activation occurs only in the first case and it is driven by charge transfer from the TM13 clusters to the CO2 molecule (i.e., CO2 –δ), which is confirmed by our Bader charge analysis and vibrational frequencies.

>i<Ab Initio>/i< investigation of the adsorption of molecules, involved in carbon dioxide and glycerol utilization, on transition-metal substrates

“…41 Moreover, adsorption can induce distortions of the nanoclusters, especially for small clusters, strongly affecting the electron density of the adsorbed system. 42,43 The electronic structure of the substrate is decisive for the adsorption process. From the density of states (DOS, expressing the number of electronic states available per energy level), the characteristics of the isolated substrate can be studied.…”

“…[52][53][54] The characteristics of CO 2 adsorbed on the different surfaces can be related to the coordination of adsorption sites, since low-coordination sites can be expected to promote stronger adsorption; [55][56][57] this has been demonstrated for the interaction between CO 2 and small 13-atom clusters containing low-coordination sites. 43,58 Hence, it should be feasible to control CO 2 adsorption through substrate particle size, since different sizes affect the availability of adsorption sites with varied coordinations. In conjunction with such characteristics of the nanoparticles, alloying can be explored in the nanoscale to further control the adsorption.…”

“…[55][56][57] Moreover, the adsorption properties have been studied for the interaction of CO 2 with various TM surfaces 52,54 and some TM nanoclusters. 43,58 There are contrasts between finite-size and extended substrates, for example, the low-coordinated adsorption sites on the small particles promote stronger adsorption, which could facilitate activation. This is an indication that the substrate particle size could play an important role in CO 2 adsorption and activation; however, the atomistic understanding of the dependence of substrate particle size on the adsorption of CO 2 and additional molecules, which are important in the electroreduction of CO 2 (such as CO, H 2 O and H 2 ), was still sparse and incomplete.…”

“…2 ), which is one of the key intermediates of CO 2 transformations. 197,199 This anionic species can be formed through the chemisorption of CO 2 on TM substrates 43,51,58,145 and its stabilization is related to a strong interaction with the substrate and donation of charge to CO 2 . 51,199 In the previous chapter, it was demonstrated that the type of TM is very important to stabilize the bent CO 2 configuration on nanoparticles and extended surfaces; based on this crucial role of the type of TM on CO 2 adsorption, there are great opportunities to tune the substrates towards target adsorption properties through alloying.…”

“…14,17,32,200 Some features that can be interesting for the adsorption and stabilization of CO δ− 2 are the sizes and morphologies of the nanoparticles, which can affect the proportions of uncoordinated and coordinated sites that can be exploited to control the adsorption strength. 43,58,145 Furthermore, tuning the composition of nanoalloys greatly increases the possibilities to design catalysts, due to the diversity of compositions, chemical orderings and synergistic effects. 15,18,201 From the staggering variety of choices to study model nanoalloys, Pt-based systems are interesting for catalytic applications, because Pt is a versatile, relatively inert, model catalyst that can provide a good balance of the catalytic activity, resistance to catalytic poisoning and substrate degradation.…”