Efficient CO₂ Electroreduction to Ethanol by Cu₃Sn Catalyst

Abstract

a key factor to evaluate the practicality of electrolysis systems with carbon footprint assessments, [7,8] the electrochemical CO 2to-ethanol production efficiency generally remains unsatisfactory, with Faradaic efficiency of ethanol production (FE ethanol ) typically below 50% and partial current densities (J ethanol ) < 200 mA cm −2 . [9,10] The generally low ethanol selectivity has been suggested due to the unfavorable adsorption of several key intermediates (i.e., *CHCHOH, *CH 2 CHOH, *CH 3 CHOH) in the ethanol formation pathway on Cu surfaces. [11,12] Heteroatomic doping is a potential means to tune the intermediate adsorption capability to improve the ethanol selectivity, which has been reported for Cu−Ag or Cu−Au systems. [13][14][15][16] For instance, Sargent and coworkers reported a bimetallic Cu−Ag catalyst with increased binding site diversity, allowing to reduce the ethylene pathway and achieve a FE ethanol as 41%. [13] A Cu−Au system was reported to increase the *CO coverage, resulting in a selectivity of producing ethanol as 48%. [14] On the other hand, considering the capital investment of the electrolysis technology, [5,6] it is also critical to search for cheap and sustainable catalyst candidates. For instance, replacing Ag with Sn can substantially reduce the catalyst cost. [17] It has also been reported that the surface coverage of *CO plays a critical role in converting CO 2 into ethanol. [18,19] Theoretical calculations of the *CO adsorption capability on Cu−Sn alloy surface have been investigated. For instance, Gokhale and coworkers reported that the existence of Sn atoms in a CuSn alloy led to the compression of Cu atoms and facilitated a higher surface coverage of *CO on Cu sites. [20] Recent studies also confirmed the favored CO-pathway on the Cu-Sn alloys with lower Sn amount (e.g., Cu 3 Sn). [21,22] On the other hand, the concept of entropy has already been introduced for analyses of binary alloys. [23] For example, Takeguchi et al. proposed an entropy-based adsorption theory that alloys with random distributions (defined by coordination state in their work with PtRu alloys) can weaken the adsorption of *CO. [24] Thus, highentropy state CuSn alloys like Cu 6 Sn 5 are possibly not suitable for *CO adsorption, [21] while a low-entropy state CuSn alloy may provide an enhanced capability for *CO adsorption and subsequent enhanced ethanol selectivity.In this work, we developed a low-entropy Cu 3 Sn electrocatalyst with substantially enhanced adsorption of *CO and *CHCHOH as key intermediates for ethanol production, featuring as efficient electrochemical CO 2 reduction to ethanol.Electrochemical carbon dioxide reduction to ethanol suggests a potential strategy to reduce the CO 2 level and generate valuable liquid fuels, while the development of low-cost catalysts with high activity and selectivity remains a major challenge. In this work, a bimetallic, low-entropy state Cu 3 Sn catalyst featuring efficient electrocatalytic CO 2 reduction to ethanol is developed. This low-entropy state Cu 3 Sn ...

Tuning Structures and Microenvironments of Cu-Based Catalysts for Sustainable CO2 and CO Electroreduction

“…Later, we reported that CuSn alloys also displayed phase-orientated selectivity. The Cu 3 Sn phase delivered a relatively high ethanol selectivity (FE ∼ 61%), while the Cu 6 Sn 5 phase facilitated the CO 2 -to-C 1 conversion toward formate and CO . X-ray absorption fine structure data revealed that the coordinate environments and configurational entropies in these two alloy phases were distinctively different, where the lower configurational entropy in Cu 3 Sn presented a higher *CO coverage and thus a preferred ethanol selectivity.…”

“…), coverage modification, and other interfacial microenvironment adjustments. In addition to the lifecycle assessment (LCA), 37 we also use techno-economic analysis to compare the market values of aqueous electrochemical systems, which are also necessary to consider for further research in this field.…”

Structure‐Tailored Surface Oxide on Cu–Ga Intermetallics Enhances CO2 Reduction Selectivity to Methanol at Ultralow Potential

“…Moreover, the nature of XANES spectra of both the intermetallic catalysts is completely different from that of both elemental Cu foil and that of Cu 2 O indicates the entirely different chemical environment of Cu in the intermetallic compounds. [ 49 ] On the other hand, in the XANES of Ga K‐edge of Cu 9 Ga 4 (Figure 5c), there is an absorption maximum at 10 378.37 eV and a shoulder at about 10 382.46 eV, which are expected from the two types of Ga present in the system (Wyckoff position: 4e and 12i), whereas CuGa 2 shows only one absorption edge (10 378.92 eV) as it has only one type of Ga site (Wyckoff position: 2h) in the crystal structure. The position of absorption maxima of both the samples resembles that of Ga metal.…”

Prospective Life Cycle Assessment Bridging Biochemical, Thermochemical, and Electrochemical CO2 Reduction toward Sustainable Ethanol Synthesis

“…32 Besides, a bimetallic, low-entropy Cu 3 Sn catalyst by Shang et al revealed an impressive FE of 64% for ethanol in CO 2saturated 0.1 M KHCO 3 in a H-type electrolyzer; however, such a H-type electrolyzer is not appropriate for continuous processes in real-world operations. 33 Besides, the Cu 3 Sn catalyst demonstrated prolonged durability of 48 h at an industrial-level current density of −900 mA cm −2 in 1 M KOH in a membrane-electrode-based electrolyzer, but a much lower FE of 40% for ethanol. On the contrary, it is worth noting that the defect-site-rich Cu catalyst (Cu -DS ) proposed by Gu et al 34 has revealed remarkable electrocatalytic CO 2 RR performance with FE values of 52 and 15% for ethanol and n-propanol at −0.95 V and 100 mA cm −2 , respectively, and prolonged stability up to 30 h in an electrochemical flow cell reactor coupled with a gas diffusion electrode (GDE).…”