(509bj) Mechanistic Insights into Alcohol Non-Oxidative Dehydrogenation Reaction on Cu and Cu-Based Alloys

Alcohol non-oxidative dehydrogenation (NODH) reaction needs no oxygen, which otherwise generates water leaving the catalyst deactivated and product distillation costlier. Therefore, NODH of bio-based alcohol like ethanol to acetaldehyde—a necessary precursor for industrial chemicals—is a sustainable route. Alcohol NODH reaction involves O–H activation followed by α-C–H cleavage to yield important aldehydes or ketones. A close-packed Cu (111) facet is active for alcohol NODH reaction. Especially NODH of primary and secondary alcohols gained research interest to obtain a wide range of intermediate chemicals like aldehyde, ketone, etc. Using 1-propanol and 2-propanol as model alcohols, we demonstrated secondary alcohol as a good candidate for NODH through density functional theory (DFT). The activation energy of O–H and C–H cleavage steps from 2-propanol precursors were 35.4 kJ/mol and 31.7 kJ/mol lower than from 1-propanol. Moreover, microkinetic modeling (MKM) of ethanol NODH on various A₃B terminated bimetallic alloys proved Ni and Cu-based alloys highly active (TOF ~ 10³â€“10⁴). Therefore, with the trends of alcohol NODH understood in Cu (111) and various bimetallic alloys, we further explore it on single atom alloys. Single atom alloys (SAAs) are composed of single metal atoms atomically dispersed on a host metal and excellent catalysts to break the scaling relations. The available experimental evidence determined Ni/Cu (111) SAA provides a lower apparent activation barrier for ethanol NODH as compared to Cu (111) and other SAAs such as Pt/Cu (111) and Pd/Cu (111). Our preliminary DFT calculations exhibit Ni single atoms in Ni/Cu (111) stabilize the ethoxy and acetaldehyde intermediates in ethanol NODH; thus, suggesting a significant role of Ni in lowering the barrier.