A reconstructed porous copper surface promotes selectivity and efficiency toward C2 products by electrocatalytic CO2 reduction.
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ABSTRACT:
SUBMITTER: Han J
PROVIDER: S-EPMC8162280 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Revealing the active nature of oxide-derived copper is of key importance to understand its remarkable catalytic performance during the cathodic CO2 reduction reaction (CO2RR) to produce valuable hydrocarbons. Using advanced spectroscopy, electron microscopy, and electrochemically active surface area characterization techniques, the electronic structure and the changes in the morphology/roughness of thermally oxidized copper thin films were revealed during CO2RR. For this purpose, we developed an in situ cell for X-ray spectroscopy that could be operated accurately in the presence of gases or liquids to clarify the role of the initial thermal oxide phase and its active phase during the electrocatalytic reduction of CO2. It was found that the Cu(I) species formed during the thermal treatment are readily reduced to Cu0 during the CO2RR, whereas Cu(II) species are hardly reduced. In addition, Cu(II) oxide electrode dissolution was found to yield a porous/void structure, where the lack of electrical connection between isolated islands prohibits the CO2RR. Therefore, the active/stable phase for CO2RR is metallic copper, independent of its initial phase, with a significant change in its morphology upon its reduction yielding the formation of a rougher surface with a higher number of underco-ordinated sites. Thus, the initial thermal oxidation of copper in air controls the reaction activity/selectivity because of the changes induced in the electrode surface morphology/roughness and the presence of more undercoordinated sites during the CO2RR.
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Project description:Lignin is an ideal carbon source material, and lignin-based carbon materials have been widely used in electrochemical energy storage, catalysis, and other fields. To investigate the effects of different lignin sources on the performance of electrocatalytic oxygen reduction, different lignin-based nitrogen-doped porous carbon catalysts were prepared using enzymolytic lignin (EL), alkaline lignin (AL) and dealkaline lignin (DL) as carbon sources and melamine as a nitrogen source. The surface functional groups and thermal degradation properties of the three lignin samples were characterized, and the specific surface area, pore distribution, crystal structure, defect degree, N content, and configuration of the prepared carbon-based catalysts were also analyzed. The electrocatalytic results showed that the electrocatalytic oxygen reduction performance of the three lignin-based carbon catalysts was different, and the catalytic performance of N-DLC was poor, while the electrocatalytic performance of N-ELC was similar to that of N-ALC, both of which were excellent. The half-wave potential (E1/2) of N-ELC was 0.82 V, reaching more than 95% of the catalytic performance of commercial Pt/C (E1/2 = 0.86 V) and proving that EL can be used as an excellent carbon-based electrocatalyst material, similar to AL.
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Project description:Carbon-based nanomaterials have been regarded as promising non-noble metal catalysts for renewable energy conversion system (e.g., fuel cells and metal-air batteries). In general, graphitic skeleton and porous structure are both critical for the performances of carbon-based catalysts. However, the pursuit of high surface area while maintaining high graphitization degree remains an arduous challenge because of the trade-off relationship between these two key characteristics. Herein, a simple yet efficient approach is demonstrated to fabricate a class of 2D N-doped graphitized porous carbon nanosheets (GPCNSs) featuring both high crystallinity and high specific surface area by utilizing amine aromatic organoalkoxysilane as an all-in-one precursor and FeCl3 ·6H2 O as an active salt template. The highly porous structure of the as-obtained GPCNSs is mainly attributed to the alkoxysilane-derived SiOx nanodomains that function as micro/mesopore templates; meanwhile, the highly crystalline graphitic skeleton is synergistically contributed by the aromatic nucleus of the precursor and FeCl3 ·6H2 O. The unusual integration of graphitic skeleton with porous structure endows GPCNSs with superior catalytic activity and long-term stability when used as electrocatalysts for oxygen reduction reaction and Zn-air batteries. These findings will shed new light on the facile fabrication of highly porous carbon materials with desired graphitic structure for numerous applications.
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Project description:An overarching challenge of the electrochemical carbon dioxide reduction reaction (eCO2RR) is finding an earth-abundant, highly active catalyst that selectively produces hydrocarbons at relatively low overpotentials. Here, we report the eCO2RR performance of two-dimensional transition metal carbide class of materials. Our results indicate a maximum methane (CH4) current density of -421.63 mA/cm2 and a CH4 faradic efficiency of 82.7% ± 2% for di-tungsten carbide (W2C) nanoflakes in a hybrid electrolyte of 3 M potassium hydroxide and 2 M choline-chloride. Powered by a triple junction photovoltaic cell, we demonstrate a flow electrolyzer that uses humidified CO2 to produce CH4 in a 700-h process under one sun illumination with a CO2RR energy efficiency of about 62.3% and a solar-to-fuel efficiency of 20.7%. Density functional theory calculations reveal that dissociation of water, chemisorption of CO2 and cleavage of the C-O bond-the most energy consuming elementary steps in other catalysts such as copper-become nearly spontaneous at the W2C surface. This results in instantaneous formation of adsorbed CO-an important reaction intermediate-and an unlimited source of protons near the tungsten surface sites that are the main reasons for the observed superior activity, selectivity, and small potential.
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Project description:The product selectivity of many heterogeneous electrocatalytic processes is profoundly affected by the liquid side of the electrocatalytic interface. The electrocatalytic reduction of CO to hydrocarbons on Cu electrodes is a prototypical example of such a process. However, probing the interactions of surface-bound intermediates with their liquid reaction environment poses a formidable experimental challenge. As a result, the molecular origins of the dependence of the product selectivity on the characteristics of the electrolyte are still poorly understood. Herein, we examined the chemical and electrostatic interactions of surface-adsorbed CO with its liquid reaction environment. Using a series of quaternary alkyl ammonium cations ([Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]), we systematically tuned the properties of this environment. With differential electrochemical mass spectrometry (DEMS), we show that ethylene is produced in the presence of [Formula: see text] and [Formula: see text] cations, whereas this product is not synthesized in [Formula: see text]- and [Formula: see text]-containing electrolytes. Surface-enhanced infrared absorption spectroscopy (SEIRAS) reveals that the cations do not block CO adsorption sites and that the cation-dependent interfacial electric field is too small to account for the observed changes in selectivity. However, SEIRAS shows that an intermolecular interaction between surface-adsorbed CO and interfacial water is disrupted in the presence of the two larger cations. This observation suggests that this interaction promotes the hydrogenation of surface-bound CO to ethylene. Our study provides a critical molecular-level insight into how interactions of surface species with the liquid reaction environment control the selectivity of this complex electrocatalytic process.
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Project description:Copper offers unique capability as catalyst for multicarbon compounds production in the electrochemical carbon dioxide reduction reaction. In lieu of conventional catalysis alloying with other elements, copper can be modified with organic molecules to regulate product distribution. Here, we systematically study to which extent the carbon dioxide reduction is affected by film thickness and porosity. On a polycrystalline copper electrode, immobilization of porous bipyridine-based films of varying thicknesses is shown to result in almost an order of magnitude enhancement of the intrinsic current density pertaining to ethylene formation while multicarbon products selectivity increases from 9.7 to 61.9%. In contrast, the total current density remains mostly unaffected by the modification once it is normalized with respect to the electrochemical active surface area. Supported by a microkinetic model, we propose that porous and thick films increase both local carbon monoxide partial pressure and the carbon monoxide surface coverage by retaining in situ generated carbon monoxide. This reroutes the reaction pathway toward multicarbon products by enhancing carbon-carbon coupling. Our study highlights the significance of customizing the molecular film structure to improve the selectivity of copper catalysts for carbon dioxide reduction reaction.
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Project description:Copper-based catalyst is uniquely positioned to catalyze the hydrocarbon formations through electrochemical CO2 reduction. The catalyst design freedom is limited for alloying copper with H-affinitive elements represented by platinum group metals because the latter would easily drive the hydrogen evolution reaction to override CO2 reduction. We report an adept design of anchoring atomically dispersed platinum group metal species on both polycrystalline and shape-controlled Cu catalysts, which now promote targeted CO2 reduction reaction while frustrating the undesired hydrogen evolution reaction. Notably, alloys with similar metal formulations but comprising small platinum or palladium clusters would fail this objective. With an appreciable amount of CO-Pd1 moieties on copper surfaces, facile CO* hydrogenation to CHO* or CO-CHO* coupling is now viable as one of the main pathways on Cu(111) or Cu(100) to selectively produce CH4 or C2H4 through Pd-Cu dual-site pathways. The work broadens copper alloying choices for CO2 reduction in aqueous phases.
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