Cu–Sn Bimetallic Catalyst for Selective Aqueous Electroreduction of CO₂ to CO

Abstract

ABSTRACT. We report a selective and stable electrocatalyst utilizing non-noble metals consisting of Cu and Sn for the efficient and selective reduction of CO 2 to CO over a wide potential range. The bimetallic electrode was prepared through the electrodeposition of Sn species on the surface of oxide-derived copper (OD-Cu). The Cu surface, when decorated with an optimal amount of Sn, resulted in a Faradaic efficiency (FE) for CO greater than 90% and a current density of −1.0 mA cm −2 at −0.6 V vs. RHE, compared to the CO FE of 63% and −2.1 mA cm −2 for OD-Cu. Excess Sn on the surface caused H 2 evolution with a decreased current density. X-ray diffraction (XRD) suggests the formation of Cu-Sn alloy. Auger electron spectroscopy of the sample surface exhibits zero-valent Cu and Sn after the electrodeposition step. Density functional theory (DFT) calculations show that replacing a single Cu atom with a Sn atom leaves the d-band orbitals mostly unperturbed, signifying no dramatic shifts in the bulk electronic structure. However, the Sn atom discomposes the multi-fold sites on pure Cu, Page 1 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 disfavoring the adsorption of H and leaving the adsorption of CO relatively unperturbed. Our catalytic results along with DFT calculations indicate that the presence of Sn on reduced OD-Cu diminishes the hydrogenation capability-i.e., the selectivity towards H 2 and HCOOH-while hardly affecting the CO productivity. While the pristine monometallic surfaces (both Cu and Sn) fail to selectively reduce CO 2 , the Cu-Sn bimetallic electrocatalyst generates a surface that inhibits adsorbed H*, resulting in improved CO FE. This study presents a strategy to provide a low-cost non-noble metals that can be utilized as a highly selective electrocatalyst for the efficient aqueous reduction of CO 2 . ACS Paragon Plus Environment ACS Catalysis

Solar conversion of CO2 to CO using Earth-abundant electrocatalysts prepared by atomic layer modification of CuO

“…SnO 2 -coated and uncoated nanowires had to be reduced before products were observed, indicating that the reduced form of the material constitutes the active catalyst, in agreement with earlier studies 15,18,24 . Detailed analysis of catalyst samples after electrochemical testing is provided in Supplementary Note 5.…”

“…Following up on this work, it was demonstrated that by electrochemically reducing copper oxide in the presence of indium ions, the selectivity toward producing CO could be substantially enhanced 16,17 . More recently, the same group demonstrated tin to have a similar effect 18 . Although adding sources of metal ions during the catalyst reduction process is effective in tuning the selectivity, it is difficult to control and may not guarantee uniform coating.…”

Investigation of Electrocatalysts for Selective Reduction of CO2 to CO: Monitoring the Reaction Products by on line Mass Spectrometry and Gas Chromatography

“…For Au and Ag, the formation of COOH* is the limiting step and determines their activities for reduction of CO 2 to CO. The additional reduction of CO to CHO* species A previous study of Sarfraz et al 60 (by density functional theory (DFT) calculations) evidenced that the substitution of a Cu atom by a Sn atom does not cause changes in the d-band structure. Consequently, the increased CO production brought by alloying Cu and Sn, in relation to that of these pure metals, would not be attributed to changes in the CO binding energy due to electronic changes.…”

“…Hence, this would suggest that, initially, the Cu 4 Sn/C electrocatalyst is covered by oxide/hydroxide species and, by decreasing the electrochemical potential down to -1.5 V, and, more severely, to -2.0 V, these species are stripped off from the surface, yielding Cu and Sn atoms in their metallic states. Despite the fact of been synthesized by a different manner, Sarfraz et al 60 by using Auger electron spectroscopy also evidenced the existence of metallic Cu and Sn on Cu-Sn alloys after the electrocatalytic reaction (low potentials). …”

Investigation of ceramics based on Cu-Sn powder obtained by plasma dynamic method

“…Another way to solve this problem is a pre-activation of copper-tin powders to improve the tribological characteristics of Cu-Sn alloy [4]. The authors of the work [5] copper-tin can more efficiently and selectively recover the CO2 to CO in a wide range of potentials [6]. This paper shows a new unique method for obtaining materials based on tin-copper in a high-speed plasma jet generated by a coaxial magnetoplasma accelerator with copper electrodes [7], as well as the creation on their basis of bulk samples using a spark plasma sintering installation.…”