Direct Synthesis of 1-Butanol with High Faradaic Efficiency from CO₂ Utilizing Cascade Catalysis at a Ni-Enhanced (Cr₂O₃)₃Ga₂O₃ Electrocatalyst

Electrochemical transformation of CO₂ into energy-dense 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 1-butanol 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, 3-hydroxybutanal becomes the primary product. This is in contrast to the nickel-free (Cr₂O₃)₃(Ga₂O₃) system, where neither 3-hydroxybutanal nor 1-butanol was detected. Mechanistic studies show that formate is the initial CO₂ 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.