Graphene-supported isolated platinum atoms and platinum dimers for CO2 hydrogenation: Catalytic activity and selectivity variations

Abstract

Manipulating catalyst structures to control product selectivity while maintaining high activity presents a considerable challenge in CO₂ hydrogenation. Combining density functional theory calculations and microkinetic analysis, we proposed that graphene-supported isolated Pt atoms (Pt₁/graphene) and Pt₂ dimers (Pt₂/graphene) exhibited distinct selectivity in CO₂ hydrogenation. Pt₁/graphene facilitated the conversion of CO₂ into formic acid, whereas Pt₂/graphene favored methanol generation. The variation in product selectivity arose from the synergistic interaction of Pt₂ dimers, which facilitated the migration of H atoms between two Pt atoms and promoted the transformation from *COOH intermediates to *C(OH)₂ intermediates, altering the reaction pathways compared to isolated Pt atoms. Additionally, an analysis of the catalytic activities of three Pt₁/graphene and three Pt₂/graphene structures revealed that the turnover frequencies for formic acid generation on Pt_1ii/graphene and methanol generation on Pt_2i/graphene were as high as 744.48 h^-1 and 789.48 h^-1, respectively. These values rivaled or even surpassed those previously reported in the literature under identical conditions. This study provides valuable insights into optimizing catalyst structures to achieve desired products in CO₂ hydrogenation