A Density Functional Theory Study on the Mechanism of Complete Ethanol Oxidation on Ir(100): Surface Diffusion-Controlled C–C Bond Cleavage

Effective C–C bond cleavage is a critical concern in the applications of ethanol technologies. The lack of catalytic efficiency toward complete ethanol oxidation reaction (EOR) has hindered the development of direct ethanol fuel cells. Ir-based catalysts have recently shown promise in the complete EOR. However, its catalytic mechanism remains unclear, which impedes the development of better Ir-based catalysts. Herein, we report a comprehensive reaction network of complete ethanol decomposition on Ir(100) based on the extensive density functional theory calculations. Our results show that decomposition of ethanol on Ir(100) consists of four sequential dehydrogenation steps that lead to the generation of CH2CO species then follows two competitive reaction pathways, namely, the C–O bond cleavage that leads to the formation of poisonous CHC species and the diffusion of CH2CO leading to complete oxidation: CH3CH2OH → CH3CH2O → CH3CHO → CH3CO → CH2CO → CH2 → CH → CHO → CO → CO2. Furthermore, the formation of acetic acid is not favored on Ir(100). This work highlights the essential roles of adsorption structure and diffusion of CH2CO in ethanol decomposition and will serve as a benchmark for future investigation of the complete EOR, such as exploring the electric and solvent effects on EOR.