Electrochemical transformation of CO 2 into energydense liquid fuels provides a viable solution to challenges regarding climate change and nonrenewable resource dependence. Here, we report on the modification of a Cr-Ga oxide electrocatalyst through the introduction of nickel to generate a catalyst that generates 1butanol at unprecedented faradaic efficiencies (ξ = 42%). This faradaic efficiency occurs at −1.48 V vs Ag/AgCl, with 1-butanol production commencing at an overpotential of 320 mV. At this potential, minor products include formate, methanol, acetic acid, acetone, and 3-hydroxybutanal. At −1.0 and −1.4 V, 3hydroxybutanal becomes the primary product. This is in contrast to the nickel-free (Cr 2 O 3 ) 3 (Ga 2 O 3 ) system, where neither 3hydroxybutanal nor 1-butanol was detected. Mechanistic studies show that formate is the initial CO 2 reduction product and identify acetaldehyde as the key intermediate. Nickel is found responsible for the coupling and reduction of acetaldehyde to generate the higher molecular weight carbon products observed. To the best of our knowledge, this is the first electrocatalyst to generate 1-butanol with high faradaic efficiency.

Elimination voltammetry with linear scan (EVLS) is an analysis method that allows the decomposition of the measured current into its capacitive, diffusional, and kinetic contributions. This method was applied to study the electro-oxidation of methanol on nickel films deposited galvanostatically on gold. This analysis suggests a strong dependence of the NiOOH formation and methanol oxidation on the scan rate. According to the EVLS deconvolution, at high scan rates (> 100 mV s−1), the oxidation of Ni(OH)2 to NiOOH has a remarkable resemblance to a reaction that proceeds in an adsorbed state. Decreasing the scan rate results in qualitative changes of the particular currents, implying the occurrence of electrochemical processes that require a larger time scale (>0.5 s), like the formation of the water intercalated γ-NiOOH. For the methanol electro-oxidation process, the main contribution comes from the kinetic current; however, increasing the scan rate reveals a parallel diffusional process related to the oxygen evolution.