Sarma Plaban J, Dowerah Dikshita, Gour Nand K, Logsdail Andrew J, Catlow C Richard A, Deka Ramesh Ch
Department of Chemical Sciences, Tezpur University, Tezpur, Assam, India.
Phys Chem Chem Phys. 2021 Jan 6;23(1):204-210. doi: 10.1039/d0cp04472e.
A density functional theory study has been performed to investigate cation-doped Sn2O4 clusters for selective catalytic reduction of CO2. We study the influence of Si and Ti dopants on the height of the H2 dissociation barrier for the doped systems, and then the subsequent mechanism for the conversion of CO2 into formic acid (FA) via a hydride pinning pathway. The lowest barrier height for H2 dissociation is observed across the 'Ti-O' bond of the Ti-doped Sn2O4 cluster, with a negatively charged hydride (Ti-H) formed during the heterolytic H2 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 Sn2O4 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 Sn2O4 clusters exhibit better catalytic activity than undoped clusters in the important process of reducing CO2 to FA when proceeding via the hydride pinning pathway.
已进行了一项密度泛函理论研究，以探究阳离子掺杂的Sn2O4团簇用于二氧化碳的选择性催化还原。我们研究了硅和钛掺杂剂对掺杂体系中H2解离势垒高度的影响，以及随后通过氢化物固定途径将二氧化碳转化为甲酸（FA）的机制。在掺杂钛的Sn2O4团簇的“Ti-O”键上观察到H2解离的最低势垒高度，在异裂H2解离过程中形成带负电荷的氢化物（Ti-H），从而对所需的FA产物产生选择性。甲酸根中间体的形成被确定为整个途径的速率决定步骤（RDS），但与未掺杂的Sn2O4团簇上的相同步骤相比，掺杂钛的体系的势垒高度大幅降低。计算得出RDS中甲酸根形成的自由能为负，这表明氢化物转移将自发发生。总体而言，我们的结果表明，在通过氢化物固定途径将二氧化碳还原为FA的重要过程中，小尺寸的掺杂钛的Sn2O4团簇比未掺杂的团簇表现出更好的催化活性。
