(140d) Strong sp-D Orbital Hybridization Driven Pt-Graphene Hybrid Catalysts for Direct CO2 Hydrogenation to Formic Acid

Formic acid (FA) is one of the most promising compounds for hydrogen storage for its high hydrogen density, non-toxicity, and great stability under ambient conditions, which can be made from CO₂. Although the noble metal or alloy catalysts have validated their outstanding activity to the dehydrogenation of FA into H₂ and CO₂, the hydrogenation of CO₂ towards FA is relatively difficult due to the nature of relatively weak CO_{2 ­}adsorption compared with HCOO adsorption on the metal surfaces. Indeed, thermal CO₂ hydrogenation to FA has been a challenge for a decade since thermal CO₂ hydrogenation is endothermic process. Therefore, the efficient transformation of CO₂ into renewable energy sources such as FA is a crucial for further development of new energy technology. In this study, we investigate the CO₂ hydrogenation towards FA at ambient temperature on a new Pt-Graphene hybrid catalyst using DFT method. This new Pt-Graphene hybrid catalyst consists of Pt monolayer and graphene via hybridizing sp and d orbitals between carbon and Pt atoms. The sp-d hybridization significantly reduces the local density of states of d-band and at the same time increases s-band near the Fermi level which leads to the strong chemisorption of CO₂ at the Pt surface. From our DFT calculations, it is discovered that the CO₂ hybridization towards FA is exothermic reaction on Pt-Graphene catalyst. Furthermore, the microkinetic modeling is implemented to identify overall turnover frequencies. By analyzing various metal-Graphene hybrid catalysts, we will also address physical and chemical intuition for the design of new hybrid catalysts.