Nickel–Gallium-Catalyzed Electrochemical Reduction of CO₂ to Highly Reduced Products at Low Overpotentials

Abstract

We report the electrocatalytic reduction of CO 2 to the highly reduced C 2 products, ethylene and ethane, as well as to the fully reduced C 1 product, methane, on three different phases of nickel−gallium (NiGa, Ni 3 Ga, and Ni 5 Ga 3 ) films prepared by drop-casting. In aqueous bicarbonate electrolytes at neutral pH, the onset potential for methane, ethylene, and ethane production on all three phases was found to be −0.48 V versus the reversible hydrogen electrode (RHE), among the lowest onset potentials reported to date for the production of C 2 products from CO 2 . Similar product distributions and onset potentials were observed for all three nickel− gallium stoichiometries tested. The onset potential for the reduction of CO 2 to C 2 products at low current densities catalyzed by nickel−gallium was >250 mV more positive than that of polycrystalline copper, and approximately equal to that of single crystals of copper, which have some of the lowest overpotentials to date for the reduction of CO 2 to C 2 products and methane. The nickel−gallium films also reduced CO to ethylene, ethane, and methane, consistent with a CO 2 reduction mechanism that first involves the reduction of CO 2 to CO. Isotopic labeling experiments with 13 CO 2 confirmed that the detected products were produced exclusively by the reduction of CO 2 .

Tuning the Products of CO2Electroreduction on a Ni3Ga Catalyst Using Carbon Solid Supports

“…z E-mail: bocarsly@princeton.edu et al 26 and Ni 3 Al electrocatalyst reported by our lab. 27 Efficacy of the Ni-Ga system, in particular, has been examined with respect to alloy composition, 26 but solid support and morphological impacts on its behavior toward CO 2 have yet to be discussed.…”

“…For this study, we focused on the Ni 3 Ga alloy after preliminary tests featuring films with 1:1, 3:1, and 5:3 stoichiometries indicated that, in our hands, the 3:1 variant was the most successful at reducing CO 2 to CO, a possible intermediate leading to more highly reduced products. 26 We show that Ni 3 Ga thin films exhibit different surface morphologies and electrocatalytic behaviors when deposited on different carbon solid supports. Furthermore, we find that unsupported, bulk Ni 3 Ga, though unreactive toward CO 2 , is a modest CO reduction catalyst capable of generating MeOH, and that introducing a carbon solid support alters this behavior to make the material more active toward the CO 2 reactant.…”

“…25 Recently, a new class of copper-free, carbon-supported, nickel alloy catalysts for CO 2 electroreduction to multi-carbon, multi-electron products has been described. These catalysts include the Ni-Ga electroreduction system analyzed by Torelli * Electrochemical Society Member.z E-mail: bocarsly@princeton.edu et al 26 and Ni 3 Al electrocatalyst reported by our lab. 27 Efficacy of the Ni-Ga system, in particular, has been examined with respect to alloy composition, 26 but solid support and morphological impacts on its behavior toward CO 2 have yet to be discussed.…”

“…These catalysts include the Ni-Ga electroreduction system analyzed by Torelli et al 26 and Ni 3 Al electrocatalyst reported by our lab. 27 Efficacy of the Ni-Ga system, in particular, has been examined with respect to alloy composition, 26 but solid support and morphological impacts on its behavior toward CO 2 have yet to be discussed. We report here that these factors are important in maximizing the system's ability to generate its highly interesting CO 2 reduction products, which are currently limited to faradaic efficiencies below 2%.…”

Recent Advances in Transition-Metal-Mediated Electrocatalytic CO2 Reduction: From Homogeneous to Heterogeneous Systems

“…Recently, Lewis and co-workers prepared Ni-Ga bimetallic films employing a drop-casting strategy with three different phases for reducing CO 2 to the highly reduced C 2 products including ethylene and ethane and C 1 -product methane [59]. In aqueous bicarbonate electrolytes at neutral pH, the onset potential was found to be −0.48 V vs. RHE, which was 0.25 V more positive than that of polycrystalline copper.…”