Localized Geometry Determined Selectivity of Iodide‐Derived Copper for Electrochemical CO₂ Reduction

Abstract

With global sustainability seriously suffering from the rapid growth of CO 2 emission from the excessive use of fossil energy, [1] the humankind has been striving for carbon neutrality by developing renewable energy technologies for reducing CO 2 emission. [2] Electrochemical CO 2 reduction, which captures and converts CO 2 into fuels and feedstocks, has been attracted extensive attention for addressing the energy and environmental problems. [3] In an electrochemical CO 2 reduction reaction (eCO 2 RR), electrocatalysts with high activity and selectivity for producing value-added multicarbon (C 2+ ) products are determinative to the realization and industrialization of this carbon-neutrality technology. [4] Among those well-developed metallic electrocatalysts (e.g., Au, Ag, Cu, Bi, and Sn, etc.), Cu is the most promising one that can reduce CO 2 to C 2+ products, due to its moderate adsorption strength for *CO intermediate at surface during the electrochemical reduction process. [5] However, the low activity, poor selectivity, and inferior stability of polycrystalline Cu toward C 2+ products have hindered its real applications for eCO 2 RR. [4b] As alternatives to polycrystalline Cu, various Cu-based eCO 2 RR catalysts with encouraging electrochemical performances have been developed by regulating the chemical compositions and engineering the crystal and electronic structures, including single-crystal Cu, [6] Cu-based alloys, [7] and oxidederived Cu (OD-Cu), [8] etc. Especially, OD-Cu has received extensive exploration as the appreciated eCO 2 RR electrocatalysts for its high selectivity of C 2+ products, benefitted from its unique localized geometry, such as rough surface, residual oxygen, and Cu + . [8b,c] For example, Yu et al. reported the superior C 2 H 4 selectivity of 45% at −1.0 V versus reversible hydrogen electrodes (RHE) for OD-Cu catalysts, which was evidenced to be attributed to the enhanced *CO adsorption and dimerization at the oxygen-bearing Cu surface with residual oxygen and Cu + species. [8c] Except for OD-Cu derived from oxides, Cu-based catalysts derived from copper halides as precursors with halogens (e.g., Cl, Br, I) readily bonded with Cu, have also been tapped on Two iodide-derived copper (ID-Cu) electrocatalysts (E-ID-Cu and W-ID-Cu) are prepared by electrochemical/wet chemical iodination of Cu foil and subsequent in situ electrochemical reduction reaction. In comparison to electropolished Cu (EP-Cu), both E-ID-Cu and W-ID-Cu can produce multicarbon (C 2+ ) products with much-improved selectivity, with Faradic efficiency (FE) reaching 64.39% for E-ID-Cu and 71.16% for W-ID-Cu at −1.1 V versus reversible hydrogen electrodes (RHE), which can be attributed to their localized geometry features with high defect density and high surface roughness. Given the well-determined FEs towards C 2+ products, the partial current densities for C 2+ production can be estimated to be 251.8 mA cm −2 for E-ID-Cu and 290.0 mA cm −2 for W-ID-Cu at −1.2 V versus RHE in a flow cell. In situ characteriza...

Electrochemical reduction of carbon dioxide to multicarbon (C2+) products: challenges and perspectives

“…Ionic effects can be explored at a static level using the nudged elastic band (NEB) method. 215 Chen and colleagues have investigated the influence of cations on the electrocatalytic pathway of CO 2 RR on Ag(111) using an explicit model combined with the NEB method. 216 The calculation shows that the local cation-induced field can significantly stabilize the key intermediates, including *CO 2 and *COOH, while reducing the overpotential for product formation.…”

Cu-based catalyst designs in CO2electroreduction: precise modulation of reaction intermediates for high-value chemical generation

“…93 Similarly, iodide-derived copper (ID-Cu) benefits from high-density defects and surface roughness, which enhance *CO adsorption by elevating the d-band center of Cu and facilitating C–C coupling on ID-Cu. 119 The doping of halogen elements induces the formation of Cu oxidation states while preserving the phase structure, resulting in strong adsorption of *CO and other carbonate intermediates on Cu δ + . Cui et al demonstrated that Cu + can be dynamically stabilized by I − in HCO 3 − electrolytes through the formation of CuI, leading to the formation of atypical Cu(CO) n + complexes with strong binding of in situ formed *CO.…”

Recent Advances in Electrochemical CO2‐to‐Multicarbon Conversion: From Fundamentals to Industrialization

“…In addition, a series of catalyst-engineering strategy as well as the novel C─C coupling mechanisms can also be visually observed assisted with In situ FT-IR method. For instance, the gradient heteroatom (N/P/S/O/B [202,203] and halogen [204] ) engineering effectively adjusted the *CO adsorption and activation on Cu surface and altered the local H proton consumption in electrolyte. And, a hydrogen-assisted C─C coupling process was proposed by Wang and co-workers via the activation of H 2 O and CO on the halogen-modified Cu surfaces to reach the hydrogenation of adsorbed CO, letting the adsorbed CHO species as key reaction intermediates for *CHO─*CHO dimerization pathway for the first time.…”

“…[313] In regard to metallic-atom local decoration, it was proposed from Zhang's group [311] and Sun's group [316] that the introduction of Ni cluster or Bi single atom on the surface of Cu active sites resulted in the alteration of binding sites to Ni─Cu or Bi─Cu bridge for *CO, favoring the subsequent C─C coupling (Figure 16d,e). While for nonmetallicatom local decoration, it was found that the electron-withdrawing groups (like ─NO 2 ) [317] and halide (e.g., F − and I − ) [79] boosted active sites to ethylene and ethanol selectivity while electrondonating groups (like ─NH 2 ) [204] benefited the acetic acid formation (Figure 16f).…”