(Keynote) Metal Enhanced Cr2O3/Ga2O3 an Efficient and Selective Electrocatalyst for the Conversion of CO2 to C2+ Products

Abstract

Binary intermetallic compounds composed of a first row transition metal and a post transition metal such as aluminum or gallium and oxides thereof provide a new source of heterogeneous electrocatalysts for the reduction of CO2. Unlike related single metal systems, which only generate formate and CO, the mixed metal systems form a variety of C2+ products. Most interestingly, we find that a nickel metal enhanced Cr2O3/Ga2O3 interface efficiently catalyzes the formation of 1-butanol.We have reported that Ni3Al reduces CO2 to a variety of C3 oxygenates,1-2 while Lewis et. al. has noted that various NixGay alloys generate C2 products from CO2.3 In both cases, the higher order products are observed in low yield. However, these examples are important since they demonstrate that metallic systems that do not contain copper can form carbon-carbon bonds from CO2. Recently, we discovered that mixed oxides of chromium-gallium containing a small concentration of nickel metal produce 1-butanol with greater than 40% faradaic yields in aqueous electrolytes.4 A variety of other C2, C3 and C4 products are also observed. These species can be selected for, by regulating the electrolyte pH, the electrode potential and the enhancing metal employed.Our new findings argue for a relatively unexplored mechanism for the formation of carbon-carbon bonds through a formate intermediate, circumventing the need to generate a CO. For all of the heterogeneous systems we have investigated, there appears to be strong correlation between the morphology of the electrocatalyst and the product distribution observed. It is also observed that the composition of the underlying electrode strongly influences the product composition. For example, while Ni3Al on glassy carbon produces a variety of C3 products, the same catalyst when placed on p-type CIGS photocathode primarily produces methanol with no indication of carbon-carbon coupling processes.5 A detailed mechanistic understanding of these systems is likely to offer new opportunities for the electrosynthesis of organic products from CO2 with high faradaic yield and modest overpotential.References Paris, A. R.; Bocarsly, A. B., Ni–Al Films on Glassy Carbon Electrodes Generate an Array of Oxygenated Organics from CO2. ACS Catalysis 2017, 7, 6815-6820. Paris, A. R.; Bocarsly, A. B., Mechanistic Insight into C2 and C3 Product Generation Using Ni3Al and Ni3Ga Electrocatalysts for CO2 Reduction. In Faraday Discussion on Artifical Photosynthesis, Royal Society of Chemistry: Cambridge University, GB, 2018. Torelli, D. A.; Francis, S. A.; Crompton, J. C.; Javier, A.; Thompson, J. R.; Brunschwig, B. S.; Soriaga, M. P.; Lewis, N. S., Nickel–Gallium-Catalyzed Electrochemical Reduction of CO2 to Highly Reduced Products at Low Overpotentials. ACS Catalysis 2016, 6 (3), 2100-2104. Cronin, S. P.; Dulovic, S.; Lawrence, J. A.; Filsinger, K. A.; Hernandez-Gonzalez, A. P.; Evans, R.; Stiles, J. W.; Morris, J.; Pelczer, I.; Bocarsly, A. B., Direct Synthesis of 1-butanol with High Faradaic Efficiency from CO2 Utilizing Cascade Catalysis at a Ni-Enhanced (Cr2O3)3Ga2O3 Electrocatalyst. J. Am. Chem. Soc. 2023, 6762–6772. Foster, B. M.; Paris, A. R.; Frick, J. J.; Blasini-Pérez, D. A.; Cava, R. J.; Bocarsly, A. B., Catalytic Mismatching of CuInSe2 and Ni3Al Demonstrates Selective Photoelectrochemical CO2 Reduction to Methanol. ACS Applied Energy Materials 2020, 3 (1), 109-113.