B‐Cu‐Zn Gas Diffusion Electrodes for CO₂ Electroreduction to C₂₊ Products at High Current Densities

Abstract

Electroreduction of CO 2 to multi-carbon products has attracted considerable attention as it provides an avenue to high-density renewable energy storage.However,the selectivity and stability under high current densities are rarely reported. Herein, B-doped Cu (B-Cu) and B-Cu-Zn gas diffusion electrodes (GDE) were developed for highly selective and stable CO 2 conversion to C 2+ products at industrially relevant current densities.T he B-Cu GDE exhibited ah igh Faradaic efficiency of 79 %f or C 2+ products formation at ac urrent density of À200 mA cm À2 and apotential of À0.45 Vvs. RHE. The long-term stability for C 2+ formation was substantially improved by incorporating an optimal amount of Zn. Operando Raman spectra confirm the retained Cu + species under CO 2 reduction conditions and the lower overpotential for *OCO formation upon incorporation of Zn, whichlead to the excellent conversion of CO 2 to C 2+ products on B-Cu-Zn GDEs.

Electrochemical Reduction of Carbon Dioxide to Ethanol: A Review

“…Further, the catalyst with a composition of 0.5BÀ Cu:0.025Zn exhibited increased FE for ethanol (31 %) and n-propanol (3 %) at À 0.45 V (vs. RHE) with total CD of À 200 mA cm À 2 . [45] In-situ Raman measurements showed that the addition of boron and Zn maintains stability of Cu + species during ECO 2 R resulting in increased ethanol selectively and the long-term stability on BÀ CuÀ Zn, however, the FE of C 2 H 5 OH was decreased at higher Zn loading due to the competing HER and excess CO production by Zn.…”

“…Although ECO 2 R has many advantages as listed earlier, but there are some challenges also which inhibit the CO 2 electroreduction performance, such as high over-potential (high energy consumption), poor product selectivity, low energy efficiency, and slow kinetics of CO 2 electrochemical reduction reaction, etc.. [19] Therefore, there is a need to develop an electro-catalyst which is highly selective, stable, cheap, and able to produce different chemicals at low over-potential with high rates without the formation of undesirable byproducts. [13,36] Numerous strategies have been developed to synthesize ethanol selective electro-catalysts, e. g. electrochemical deposition, [37][38][39] hydrothermal synthesis, [40] thermal annealing, [41,42] chemical reduction of different metal salts [43][44][45] and soft templating method. [46,47] Most of these methods undergo oxidation step followed by an in-situ reduction to metallic state during ECO 2 R. In this section, the preparation of Table 2.…”

“…Authors reported one-step process of chemical reduction of copper(II) chloride (CuCl 2 ) using sodium borohydride (NaBH 4 ) for the synthesis of boron-doped copper (BÀ Cu). Song et al [45] synthesized B-doped Cu (BÀ Cu) gas diffusion electrode (GDE) using similar method of chemical reduction of CuCl 2 with NaBH 4 and later, BÀ CuÀ Zn GDE was developed by adding Zn nanosheets in BÀ Cu nanoparticles on a carbon paper as support for ECO 2 R to C 2 + products at higher CD. In the year 2019, Li et al [120] introduced boron-doped Cu (CuÀ B) and phosphorus-doped Cu (CuÀ P) electrodes, prepared using chemical plating and electrodeposition technique, respectively.…”

“…[133] However, CuO and Cu 2 O are commonly reported to produce ethanol with high efficiency. [45,60,108,119] The reports also reveal that the interface between oxide Cu species and adjacent metallic Cu sites is responsible for higher production of C 2 + products by improved CÀ C coupling. [61] Cu δ + sites in copper electro-catalysts have been considered as active sites for ethanol production via ECO 2 R; indeed, incorporating Cu δ + into copper catalysts has resulted in producing ethanol with higher selectivity.…”

Process Parameters in the Electrochemical Reduction of Carbon Dioxide to Ethylene

“…Only recently has acknowledgment of this potentially significant problem been alluded to by Song et al. who employed flakes of zinc as sacrificial cathodes within the structure of their copper particle‐based cathodes 168. Whilst this might present a short‐term solution, this phenomenon is another significant constraint in this challenging process, one that might require a major reconsideration of the viability of utilizing alkali metal cations in alkaline electrolytes.…”