Electrocatalytic CN coupling between carbon dioxide and nitrate has emerged to meet the comprehensive demands of carbon footprint closing, valorization of waste, and sustainable manufacture of urea. However, the identification of catalytic active sites and the design of efficient electrocatalysts remain a challenge. Herein, the synthesis of urea catalyzed by copper single atoms decorated on a CeO2 support (denoted as Cu1–CeO2) is reported. The catalyst exhibits an average urea yield rate of 52.84 mmol h−1 gcat.−1 at −1.6 V versus reversible hydrogen electrode. Operando X‐ray absorption spectra demonstrate the reconstitution of copper single atoms (Cu1) to clusters (Cu4) during electrolysis. These electrochemically reconstituted Cu4 clusters are real active sites for electrocatalytic urea synthesis. Favorable CN coupling reactions and urea formation on Cu4 are validated using operando synchrotron‐radiation Fourier transform infrared spectroscopy and theoretical calculations. Dynamic and reversible transformations of clusters to single‐atom configurations occur when the applied potential is switched to an open‐circuit potential, endowing the catalyst with superior structural and electrochemical stabilities.

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...

Single-atom catalysts have already been widely investigated for the nitrogen reduction reaction (NRR). However, the simplicity of a single atom as an active center encounters the challenge of modulating the multiple reaction intermediates during the NRR process. Moving toward the single-atom-dimer (SAD) structures can not only buffer the multiple reaction intermediates but also provide a strategy to modify the electronic structure and environment of the catalysts. Here, a structure of a vanadium SAD (V-O-V) catalyst on N-doped carbon (O-V 2 -NC) is proposed for the electrochemical nitrogen reduction reaction, in which the vanadium dimer is coordinated with nitrogen and simultaneously bridged by one oxygen. The oxygen-bridged metal atom dimer that has more electron deficiency is perceived to be the active center for nitrogen reduction. A loop evolution of the intermediate structure was found during the theoretical process simulated by density functional theory (DFT) calculation. The active center V-O-V breaks down to V-O and V during the protonation process and regenerates to the original V-O-V structure after releasing all the nitrogen species. Thus, the O-V 2 -NC structure presents excellent activity toward the electrochemical NRR, achieving an outstanding faradaic efficiency (77%) along with the yield of 9.97 μg h −1 mg −1 at 0 V (vs RHE) and comparably high ammonia yield (26 μg h −1 mg −1 ) with the FE of 4.6% at −0.4 V (vs RHE). This report synthesizes and proves the peculiar V-O-V dimer structure experimentally, which also contributes to the library of SAD catalysts with superior performance.

Electrocatalytic conversion of biomass platform chemicals to jet fuel precursors is a promising approach to alleviate the energy crisis caused by the excessive exploitation and consumption of non-renewable fossil fuels. However, an aqueous electrolyte has been rarely studied. In this study, we demonstrate an anodic electrocatalysis route for producing jet fuel precursors from biomass platform chemicals on Ni-based electrocatalysts in an aqueous electrolyte at room temperature and atmosphere pressure. The desired product exhibited high selectivity for the jet fuel precursor (95.4%) and an excellent coulombic efficiency of 210%. A series of in situ characterizations demonstrated that Ni2+ species were the active sites for the coupling process. In addition, the coupling reaction could be achieved by generating radical cations and inhibiting the side reaction. First, the electrochemical process could activate the furfural (FF) molecule and generate radical cations, resulting in an average of 2.0 times chain propagation. The levulinic acid (LA) molecules played a vital role in the coupling reaction. The adsorption strength of LA on Ni3N was higher than that of FF, which could inhibit the side reaction (the oxidation of FF) and achieve high selectivity. Meanwhile, the LA molecules were adsorbed on the Ni3N surface and then disrupted the formation of Ni3+ species, thus favoring the coupling reaction. This work demonstrates an efficient route to produce jet fuel precursors directly from biomass platform chemicals and provides a comprehensive understanding of the anodic coupling process.

Oxide-derived Cu (ODÀ Cu) featured with surface located sub-20 nm nanoparticles (NPs) created via surface structure reconstruction was developed for electrochemical CO 2 reduction (ECO 2 RR). With surface adsorbed hydroxyls (OH ad ) identified during ECO 2 RR, it is realized that OH ad , sterically confined and adsorbed at ODÀ Cu by surface located sub-20 nm NPs, should be determinative to the multi-carbon (C 2 ) product selectivity. In situ spectral investigations and theoretical calculations reveal that OH ad favors the adsorption of lowfrequency *CO with weak C�O bonds and strengthens the *CO binding at ODÀ Cu surface, promoting *CO dimerization and then selective C 2 production. However, excessive OH ad would inhibit selective C 2 production by occupying active sites and facilitating competitive H 2 evolution. In a flow cell, stable C 2 production with high selectivity of ~60 % at À 200 mA cm À 2 could be achieved over ODÀ Cu, with adsorption of OH ad well steered in the fast flowing electrolyte.