Shyama Mandal1,2,Gennaro Liccardo1,2,Bang Nhan1,Matteo Cargnello1,2,Stacey Bent1,2,Frank Abild-Pedersen2
Stanford University1,SLAC National Accelerator Laboratory2
Shyama Mandal1,2,Gennaro Liccardo1,2,Bang Nhan1,Matteo Cargnello1,2,Stacey Bent1,2,Frank Abild-Pedersen2
Stanford University1,SLAC National Accelerator Laboratory2
The catalytic performance of Pt-based metals has long been recognized for its remarkable activity. Nevertheless, the sintering of Pt during the reactions diminishes its active sites, ultimately resulting in reduced reactivity. Therefore, it is imperative to inhibit the sintering of Pt during the reactions. In this context, we have conducted atomic layer deposition (ALD) of Al<sub>2</sub>O<sub>3</sub> and ZrO<sub>2</sub> onto Pt nanoparticles and observed the prevention of sintering. For a comprehensive understanding of this phenomenon, we focused on the theoretical investigation on Pt(111) terrace sites and Pt(211) step sites. Step sites are particularly susceptible to detachment, which can lead to Ostwald ripening, ultimately resulting in the deposition on larger nanoparticles. During our investigation, we considered various ALD species that could form during the process and calculated their binding energies on terrace and step sites. Our calculations revealed that most of the species exhibited a preference for binding to step sites, suggesting their ability to stabilize the steps. Additionally, we proposed a possible ALD mechanism and calculated the reaction free energies for each elementary steps on both the ALD recipes. These calculations indicated that the most favorable intermediate on Pt(211) step sites would be Al<sub>2</sub>(OH)<sub>6</sub> and Zr(OH)<sub>4</sub> for the Al<sub>2</sub>O<sub>3</sub>-based and ZrO<sub>2</sub>-based ALD processes, respectively. The ALD sample exhibited lower catalytic activity compared to Pt supported on Al<sub>2</sub>O<sub>3</sub> during combustion of propene. However, an increase in catalytic activity has been observed after aging the ALD sample. This could be attributed to the opening of the ALD layers during aging or the diffusion of Pt through defects in the ALD layer. Notably, our calculated binding energies showed that Pt has a stronger binding within the ALD layer, suggesting the possibility of Pt diffusion through the ALD layer and its subsequent participation in the catalytic reaction. In summary, our research demonstrates that even trace amounts of ALD can effectively stabilize supported Pt catalysts, mitigating sintering-related deactivation and significantly enhancing the efficiency of the catalyst.