Tuning the transition barrier of H dissociation in the hydrogenation of CO to formic acid on Ti-doped SnO clusters

• Published in: Physical chemistry chemical physics : PCCP 2021-01, Vol.23 (1), p.24-21
• Main Authors: Sarma, Plaban J, Dowerah, Dikshita, Gour, Nand K, Logsdail, Andrew J, Catlow, C. Richard A, Deka, Ramesh Ch
• Format: Article
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d0cp04472e

A density functional theory study has been performed to investigate cation-doped Sn 2 O 4 clusters for selective catalytic reduction of CO 2 . We study the influence of Si and Ti dopants on the height of the H 2 dissociation barrier for the doped systems, and then the subsequent mechanism for the conversion of CO 2 into formic acid (FA) via a hydride pinning pathway. The lowest barrier height for H 2 dissociation is observed across the 'Ti-O' bond of the Ti-doped Sn 2 O 4 cluster, with a negatively charged hydride (Ti-H) formed during the heterolytic H 2 dissociation, bringing selectivity towards the desired FA product. The formation of a formate intermediate is identified as the rate-determining step (RDS) for the whole pathway, but the barrier height is substantially reduced for the Ti-doped system when compared to the same steps on the undoped Sn 2 O 4 cluster. The free energy of formate formation in the RDS is calculated to be negative, which reveals that the hydride transfer would occur spontaneously. Overall, our results show that the small-sized Ti-doped Sn 2 O 4 clusters exhibit better catalytic activity than undoped clusters in the important process of reducing CO 2 to FA when proceeding via the hydride pinning pathway. Schematic representation of Ti-doping on a pure Sn 2 O 4 cluster for the hydrogenation of CO 2 to HCOOH via a hydride pathway.