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CO2RR performance of Cu(Tpy)2@GC and Cu(Tpy)2-KB@GC electrocatalysts a Linear sweep voltammetry of neat Cu(Tpy)2@GC and Cu(Tpy)2-KB@GC in a CO2-saturated 0.5 M KHCO3 electrolyte. b FEs for CO and H2 production of neat KB@GC, Tpy@GC, Cu(Tpy)2@GC and Cu(Tpy)2-KB@GC. c FE(CO)s of Cu(Tpy)2@GC and Cu(Tpy)2-KB@GC at different applied potentials. d TOFs calculated for Cu(Tpy)2-KB@GC at different potentials. e Chronoamperometry and FEs for CO formation at a fixed potential of −0.6 V vs. RHE for Cu(Tpy)2-KB@GC. Error bars represent the standard deviations from three independent measurements.
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The implementation of low-cost transition-metal complexes in CO2 reduction reaction (CO2RR) is hampered by poor mechanistic understanding. Herein, a carbon-supported copper bis-(terpyridine) complex enabling facile kilogram-scale production of the catalyst is developed. We directly observe an intriguing baton-relay-like mechanism of active sites tr...
Citations
... The modern in situ Raman spectroscopy has been extensively used to investigate the mechanism of HER 28 , OER 29 and oxygen reduction reaction (ORR) 30 . Moreover, by combining the in situ Raman spectroscopy with density functional theory (DFT) calculations, the structures of the intermediates can be clearly identified so that the mechanisms of the reaction can be fully discovered 31,32 . ...
The non-classical anodic H2 production from 5-hydroxymethylfurfural (HMF) is very appealing for energy-saving H2 production with value-added chemical conversion due to the low working potential (~0.1 V vs RHE). However, the reaction mechanism is still not clear due to the lack of direct evidence for the critical intermediates. Herein, the detailed mechanisms are explored in-depth using in situ Raman and Infrared spectroscopy, isotope tracking, and density functional theory calculations. The HMF is observed to form two unique inter-convertible gem-diol intermediates in an alkaline medium: 5-(Dihydroxymethyl)furan-2-methanol anion (DHMFM⁻) and dianion (DHMFM²⁻). The DHMFM²⁻ is easily oxidized to produce H2 via H⁻ transfer, whereas the DHMFM⁻ is readily oxidized to produce H2O via H⁺ transfer. The increases in potential considerably facilitate the DHMFM⁻ oxidation rate, shifting the DHMFM⁻ ↔ DHMFM²⁻ equilibrium towards DHMFM⁻ and therefore diminishing anodic H2 production until it terminates. This work captures the critical intermediate DHMFM²⁻ leading to hydrogen production from aldehyde, unraveling a key point for designing higher performing systems.
... The application of electrocatalysis towards the carbon dioxide reduction reaction (CO 2 RR), coupled with the utilization of renewable energy sources, offers a sustainable and promising opportunity to produce high value carbon-based fuels and chemicals while closing the anthropogenic carbon cycle 1, 2 . The typical products from the CO 2 RR process are carbon monoxide (CO) [3][4][5][6][7] and formic acid (HCOOH) 8-13 . ...
Effective electrocatalysts with high activity and selectivity for carbon dioxide (CO 2 ) reduction to multi-carbon (C 2+ ) products are still lacking. CO dimerization to C 2+ products such as ethylene and ethanol can be achieved on Cu-based catalysts, but direct coupling to ethane (C 2 H 6 ) has not been realized. Here, we show high selectivity of CO 2 to C 2 H 6 at room temperature and ambient pressure. Specifically, we report both experimental and theoretical findings for the Ti 2 N electrocatalyst, that exhibits the highest reported Faradaic efficiency (FE) for C 2 H 6 (~ 46.8%) at a current density of 25 mA cm − 2 and potential of -1.44 V versus the reversible hydrogen electrode (RHE) with ethane energy efficiency of ~ 20%. We achieve this outstanding performance via an alternative reaction pathway, where the *CH 3 OH adsorbed species are stabilized on the catalyst surface, which facilitates the production of C 2 H 6 through the *CH 3 OH coupling mechanism as corroborated by density functional theory (DFT). We demonstrate that the high selectivity is accompanied by excellent catalytic, structural, and electronic stability as evidenced by XAS, TEM, FTIR and SEM measurements. These groundbreaking chemistry advancements and catalysts unveil uncharted avenues for converting CO 2 into liquid fuels and chemicals.
... The picosecond pulse radiolysis coupled with transient absorption spectroscopy (ELYSE platform, Paris-Saclay University) could form e aq − in CO 2 -saturated aqueous conditions within 7 ps, and e aq − reacts directly and quantitatively with CO 2 forming CO 2 •− radicals with an almost diffusioncontrolled rate (8 × 10 9 M −1 s −1 ) within 10 ns. Until now, the current in situ/operando spectroscopic measurements on CO 2 reduction were performed with limited time resolution in a few studies with subsecond time resolution based on infrared, Raman, MS, and XAS 30,[36][37][38] . Compared to these spectroscopic techniques based on molecular vibration or photoelectron excitation, transient absorption profiles can disclose the electronic transition of surface-bound intermediates on metallic nanocatalysts with the nanosecond time resolution, which allows for the direct observation of the reaction between CO 2 •− and nanoparticles (NPs) as well as their stability kinetics on the surfaces. ...
Time-resolved identification of surface-bound intermediates on metallic nanocatalysts is imperative to develop an accurate understanding of the elementary steps of CO2 reduction. Direct observation on initial electron transfer to CO2 to form surface-bound CO2•− radicals is lacking due to the technical challenges. Here, we use picosecond pulse radiolysis to generate CO2•⁻ via aqueous electron attachment and observe the stabilization processes toward well-defined nanoscale metallic sites. The time-resolved method combined with molecular simulations identifies surface-bound intermediates with characteristic transient absorption bands and distinct kinetics from nanosecond to the second timescale for three typical metallic nanocatalysts: Cu, Au, and Ni. The interfacial interactions are further investigated by varying the important factors, such as catalyst size and the presence of cation in the electrolyte. This work highlights fundamental ultrafast spectroscopy to clarify the critical initial step in the CO2 catalytic reduction mechanism.
... For the initial coadsorption of NO 2 and CO 2 on the In(OH) 3 catalyst studied by Chade Lv et al. [30] to synthesize urea, it is not feasible on the catalyst in this study. In this regard, a novel urea synthesis method for iron-nickel metal two-site catalysts was explored according to Zhang et al.'s team [84]. Figure 5a shows the coupling competition process when nitrate is protonated to *NO intermediate. ...
Catalytic synthesis of urea is a bright substitutable to Haber–Bosch progression and industrial urea synthesis. Electrochemical C–N coupling of carbon dioxide and nitrogen oxides under environmental conditions is a newly developed method, which also provides a novel opinion for solving nitrate contamination. Conjugated organic frameworks (COFs) have been used as prospective electrocatalysts for nitrogen reduction reactions and carbon dioxide reduction reactions (CO2RR) as a result of their regulate structure and multihole properties, resulting in efficient electron transfer. This paper reports the efficient synthesis of urea from carbon dioxide and nitrate over MoM1S-Pc-M2PPs COF (M as a transition metal) electrocatalyst. According to the calculation of DFT, it was found that it was difficult for carbon dioxide and nitrogen oxide to coadsorb on MoM1S-Pc to synthesize urea, so we chose to synthesize CO on the metal porphyrin (M2PPs) structural unit, and then overflow on the bimetallic phthalocyanine and nitrogen oxide to synthesize urea. The possibility of nitrate adsorption on different catalysts was verified by calculation. We screened the stability, nitrate adsorption strength, and catalytic activity of MoM1S-Pc candidates, and the results showed that the most promising candidate catalyst was MoFeS-Pc. At the same time, the CO2RR M2PPs substrate was also screened, and the VPPs structure was selected as the best. In the study of coupling between different nitrogen-containing intermediates and *CO, the C–N coupling mechanism shows that *NOH and *CO are two possible C–N coupling nitrogen intermediates, which are shown to be thermodynamically spontaneous and have an inferior activation barrier. This study not only provisions novel perceptions into urea synthesis by coupling nitrogen oxides with carbon dioxide under environmental conditions, but also paves the way for boosting the sustainable production of carbon and nitrogen-coupled products.
Electrocatalysis is a very attractive way to achieve a sustainable carbon cycle by converting CO 2 into organic fuels and feedstocks. Therefore, it is crucial to design advanced electrocatalysts by understanding the reaction mechanism of electrochemical CO 2 reduction reaction (eCO 2 RR) with multiple electron transfers. Among electrocatalysts, dual‐atom catalysts (DACs) are promising candidates due to their distinct electronic structures and extremely high atomic utilization efficiency. Herein, the eCO 2 RR mechanism and the identification of intermediates using advanced characterization techniques, with a particular focus on regulating the critical intermediates are systematically summarized. Further, the insightful understanding of the functionality of DACs originates from the variable metrics of electronic structures including orbital structure, charge distribution, and electron spin state, which influences the active sites and critical intermediates in eCO 2 RR processes. Based on the intrinsic relationship between variable metrics and critical intermediates, the optimized strategies of DACs are summarized containing the participation of synergistic atoms, engineering of the atomic coordination environment, regulation of the diversity of central metal atoms, and modulation of metal‐support interaction. Finally, the challenges and future opportunities of atomically dispersed catalysts for eCO 2 RR processes are discussed.
Electrocatalytic CO2 reduction (CO2RR) to alcohols offers a promising strategy for converting waste CO2 into valuable fuels/chemicals but usually requires large overpotentials. Herein, we report a catalyst comprising unique oxygen-bridged Cu binuclear sites (CuOCu-N4) with a Cu···Cu distance of 3.0−3.1 Å and concomitant conventional Cu−N4 mononuclear sites on hierarchical nitrogen-doped carbon nanocages (hNCNCs). The catalyst exhibits a state-of-the-art low overpotential of 0.19 V (versus reversible hydrogen electrode) for ethanol and an outstanding ethanol Faradaic efficiency of 56.3% at an ultralow potential of −0.30 V, with high-stable Cu active-site structures during the CO2RR as confirmed by operando X-ray adsorption fine structure characterization. Theoretical simulations reveal that CuOCu-N4 binuclear sites greatly enhance the C−C coupling at low potentials, while Cu-N4 mononuclear sites and the hNCNC supportincrease the local CO concentration and ethanol production on CuOCu-N4. This study provides a convenient approach to advanced Cu binuclear site catalysts for CO2RR to ethanol with a deep understanding of the mechanism.
Optimized catalytic properties and reactant adsorption energy played a crucial role in promoting CO2 electrocatalysis. Herein, Cu7S4/Cu underwent in situ dynamic restructuring to generate S−Cu2O/Cu hybrid catalyst for effective electrochemical CO2 reduction to formate that outperformed Cu2O/Cu and Cu7S4. Thermodynamic and in situ Raman spectra revealed that the optimized adsorption of the HCOO* intermediate on S−Cu2O/Cu was regulated and the H2 pathway (surface H) was suppressed by S‐doping. Meanwhile, Cu7S4/Cu nanoflowers created abundant boundaries for ECR and strengthened the CO2 adsorption by inducing Cu. These findings provide a new perspective on synthetic methods for various electrocatalytic reduction processes.
