Exploring the reaction mechanism of ethanol synthesis from acetic acid over the Ni2In (100) surface

A low-cost and high-efficiency nickel-indium bimetallic catalyst is designed to improve the activity of acetic acid hydrogenation to ethanol, which can take full use of the overproduced acetic acid. In this work, density functional theory (DFT) calculation is carried out to explore the mechanism of ethanol synthesis from acetic acid on the Ni2In (100) surface and tailor the catalyst to an enhanced properties. The results show that the most feasible pathway is CH3COOH→CH3CO→CH3CHO→CH3CHOH→CH3CH2OH, and the rate-determining step is the hydrogenation of CH3CHOH* to CH3CH2OH, with the activation barrier of 1.20 eV and endothermic energy of 0.15 eV. Compared with the Cu2In (100) surface, the Ni2In (100) surface convert the reaction pathway to the acetyl species direction, which shows great advantages for the following CH3CHO* formation. Furthermore, the effects of indium doping in the nickel catalyst on the side reaction is also discussed by comparing with the monometallic Ni (111) surface. The addition of indium turns out to possess a significant inhibition on the C-C bond breaking and is beneficial for promoting the acetic acid hydrogenation to ethanol. Electronic analysis proved that the role of In was electron donors, which increased the electron density of Ni and enhanced the catalytic activity.