Co-activation of CH4 and CO2 for C-C bond formation on IrO2(110) surface: A combined DFT and microkinetic study

The catalytic conversion of CH4 and CO2 into acetic acid presents a sustainable strategy for mitigating greenhouse gas emissions. However, activating these stable molecules and achieving the crucial C-C bond formation remain significant challenges. Owing to its recognized ability to activate methane at low temperatures, IrO2(110) emerges as a promising catalyst for this transformation. In this study, density functional theory (DFT) calculations are employed to investigate the co-conversion of CH4 and CO2 to acetic acid on IrO2(110) surface. The Ircus and Obr sites are identified as key in facilitating the activation of both reactants, leading to the formation of the CH2COO intermediate via C-C coupling between CH2 and CO2. Microkinetic modeling reveals that acetic acid production becomes significant above 700 K, with a turnover frequency (TOF) of 1.03 x 10-6 s-1 at 800 K and 1 bar, increasing to 3.48 x 10-3 s-1 at 1000 K and 30 bar. Although these TOF values show encouraging catalytic behavior of IrO2(110), they are still relatively low, underscoring the need for further enhancement of intrinsic activity.