1
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Electrode Surface Heating with Organic Films Improves CO 2 Reduction Kinetics on Copper. ACS ENERGY LETTERS 2024; 9:1440-1445. [PMID: 38633999 PMCID: PMC11019637 DOI: 10.1021/acsenergylett.4c00204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 02/24/2024] [Accepted: 03/07/2024] [Indexed: 04/19/2024]
Abstract
Management of the electrode surface temperature is an understudied aspect of (photo)electrode reactor design for complex reactions, such as CO2 reduction. In this work, we study the impact of local electrode heating on electrochemical reduction of CO2 reduction. Using the ferri/ferrocyanide open circuit voltage as a reporter of the effective reaction temperature, we reveal how the interplay of surface heating and convective cooling presents an opportunity for cooptimizing mass transport and thermal assistance of electrochemical reactions, where we focus on reduction of CO2 to carbon-coupled (C2+) products. The introduction of an organic coating on the electrode surface facilitates well-behaved electrode kinetics with near-ambient bulk electrolyte temperature. This approach helps to probe the fundamentals of thermal effects in electrochemical reactions, as demonstrated through Bayesian inference of Tafel kinetic parameters from a suite of high throughput experiments, which reveal a decrease in overpotential for C2+ products by 0.1 V on polycrystalline copper via 60 °C surface heating.
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2
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A parallel line probe for spatially selective electrochemical NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 361:107666. [PMID: 38537481 DOI: 10.1016/j.jmr.2024.107666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 03/03/2024] [Accepted: 03/21/2024] [Indexed: 04/20/2024]
Abstract
In situ NMR is a valuable tool for studying electrochemical devices, including redox flow batteries and electrocatalytic reactors, capable of detecting reaction intermediates, metastable states, time evolution of processes or monitoring stability as a function of electrochemical conditions. Here we report a parallel line detector for spatially selective in situ electrochemical NMR spectroscopy. The detector consists of 17 copper wires and is doubly tuned to 1H/19F and X nuclei ranging from 63Cu (106.1 MHz) to 7Li (155.5 MHz). The flat geometry of the parallel line detector allows its insertion into a high electrode surface-to-volume electrochemical flow reactor, enabling a detector-in-a-reactor design. This integrated device is named "eReactor NMR probe". Combined with B1-selective pulse sequences, selective detection of the nuclei at the electrode-electrolyte interface, that is within a distance of 800 μm from the electrode surface, has been achieved. The selective detection of 7Li and 19F nuclei is demonstrated using two electrolytes, LiCl and LiBF4 solutions, respectively. A good B1 homogeneity with an 810° to 90° pulse intensity ratio of 68-72 % was achieved. Using electrochemical plating of lithium metal as a model reaction, we further demonstrated the operando functionality of the probe. The new eReactor NMR probe offers a general method for studying flow electrochemistry, and we envision applications in a wide range of environmentally relevant energy systems, for example, Li metal batteries, electrochemical ammonia synthesis, carbon dioxide capture and reduction, redox flow batteries, fuel cells, water desalination, lignin oxidation etc.
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3
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Extending Ring-Chain Coupling Empirical Law to Lithium-Mediated Electrochemical Ammonia Synthesis. Angew Chem Int Ed Engl 2024; 63:e202311413. [PMID: 38009687 DOI: 10.1002/anie.202311413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Revised: 11/23/2023] [Accepted: 11/24/2023] [Indexed: 11/29/2023]
Abstract
With its efficient nitrogen fixation kinetics, electrochemical lithium-mediated nitrogen reduction reaction (LMNRR) holds promise for replacing Haber-Bosch process and realizing sustainable and green ammonia production. However, the general interface problem in lithium electrochemistry seriously impedes the further enhancement of LMNRR performance. Inspired by the development history of lithium battery electrolytes, here, we extend the ring-chain solvents coupling law to LMNRR system to rationally optimize the interface during the reaction process, achieving nearly a two-fold Faradaic efficiency up to 54.78±1.60 %. Systematic theoretical simulations and experimental analysis jointly decipher that the anion-rich Li+ solvation structure derived from ring tetrahydrofuran coupling with chain ether successfully suppresses the excessive passivation of electrolyte decomposition at the reaction interface, thus promoting the mass transfer of active species and enhancing the nitrogen fixation kinetics. This work offers a progressive insight into the electrolyte design of LMNRR system.
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4
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Stability Issues in Electrochemical CO 2 Reduction: Recent Advances in Fundamental Understanding and Design Strategies. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2306288. [PMID: 37562821 DOI: 10.1002/adma.202306288] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/08/2023] [Indexed: 08/12/2023]
Abstract
Electrochemical CO2 reduction reaction (CO2 RR) offers a promising approach to close the anthropogenic carbon cycle and store intermittent renewable energy in fuels or chemicals. On the path to commercializing this technology, achieving the long-term operation stability is a central requirement but still confronts challenges. This motivates to organize the present review to systematically discuss the stability issue of CO2 RR. This review starts from the fundamental understanding on the destabilization mechanisms of CO2 RR, with focus on the degradation of electrocatalyst and change of reaction microenvironment during continuous electrolysis. Subsequently, recent efforts on catalyst design to stabilize the active sites are summarized, where increasing atomic binding strength to resist surface reconstruction is highlighted. Next, the optimization of electrolysis system to enhance the operation stability by maintaining reaction microenvironment especially mitigating flooding and carbonate problems is demonstrated. The manipulation on operation conditions also enables to prolong CO2 RR lifespan through recovering catalytically active sites and mass transport process. This review finally ends up by indicating the challenges and future opportunities.
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5
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A Quantitative Analysis of Electrochemical CO 2 Reduction on Copper in Organic Amide and Nitrile-Based Electrolytes. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:12857-12866. [PMID: 37465054 PMCID: PMC10350962 DOI: 10.1021/acs.jpcc.3c01955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 06/13/2023] [Indexed: 07/20/2023]
Abstract
Aqueous electrolytes used in CO2 electroreduction typically have a CO2 solubility of around 34 mM under ambient conditions, contributing to mass transfer limitations in the system. Non-aqueous electrolytes exhibit higher CO2 solubility (by 5-8-fold) and also provide possibilities to suppress the undesired hydrogen evolution reaction (HER). On the other hand, a proton donor is needed to produce many of the products commonly obtained with aqueous electrolytes. This work investigates the electrochemical CO2 reduction performance of copper in non-aqueous electrolytes based on dimethylformamide (DMF), n-methyl-2-pyrrolidone (NMP), and acetonitrile (ACN). The main objective is to analyze whether non-aqueous electrolytes are a viable alternative to aqueous electrolytes for hydrocarbon production. Additionally, the effects of aqueous/non-aqueous anolytes, membrane, and the selection of a potential window on the electrochemical CO2 reduction performance are addressed in this study. Experiments with pure DMF and NMP mainly produced oxalate with a faradaic efficiency (FE) reaching >80%; however, pure ACN mainly produced hydrogen and formate due to the presence of more residual water in the system. Addition of 5% (v/v) water to the non-aqueous electrolytes resulted in increased HER and formate production with negligible hydrocarbon production. Hence, we conclude that aqueous electrolytes remain a better choice for the production of hydrocarbons and alcohols on a copper electrode, while organic electrolytes based on DMF and NMP can be used to obtain a high selectivity toward oxalate and formate.
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6
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NMR-based quantification of liquid products in CO 2 electroreduction on phosphate-derived nickel catalysts. Commun Chem 2023; 6:147. [PMID: 37430001 DOI: 10.1038/s42004-023-00948-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Accepted: 06/30/2023] [Indexed: 07/12/2023] Open
Abstract
Recently discovered phosphate-derived Ni catalysts have opened a new pathway towards multicarbon products via CO2 electroreduction. However, understanding the influence of basic parameters such as electrode potential, pH, and buffer capacity is needed for optimized C3+ product formation. To this end, rigorous catalyst evaluation and sensitive analytical tools are required to identify potential new products and minimize increasing quantification errors linked to long-chain carbon compounds. Herein, we contribute to enhance testing accuracy by presenting sensitive 1H NMR spectroscopy protocols for liquid product assessment featuring optimized water suppression and reduced experiment time. When combined with an automated NMR data processing routine, samples containing up to 12 products can be quantified within 15 min with low quantification limits equivalent to Faradaic efficiencies of 0.1%. These developments disclosed performance trends in carbon product formation and the detection of four hitherto unreported compounds: acetate, ethylene glycol, hydroxyacetone, and i-propanol.
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7
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How Temperature Affects the Selectivity of the Electrochemical CO 2 Reduction on Copper. ACS Catal 2023; 13:8080-8091. [PMID: 37342834 PMCID: PMC10278069 DOI: 10.1021/acscatal.3c00706] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/22/2023] [Indexed: 06/23/2023]
Abstract
Copper is a unique catalyst for the electrochemical CO2 reduction reaction (CO2RR) as it can produce multi-carbon products, such as ethylene and propanol. As practical electrolyzers will likely operate at elevated temperatures, the effect of reaction temperature on the product distribution and activity of CO2RR on copper is important to elucidate. In this study, we have performed electrolysis experiments at different reaction temperatures and potentials. We show that there are two distinct temperature regimes. From 18 up to ∼48 °C, C2+ products are produced with higher Faradaic efficiency, while methane and formic acid selectivity decreases and hydrogen selectivity stays approximately constant. From 48 to 70 °C, it was found that HER dominates and the activity of CO2RR decreases. Moreover, the CO2RR products produced in this higher temperature range are mainly the C1 products, namely, CO and HCOOH. We argue that CO surface coverage, local pH, and kinetics play an important role in the lower-temperature regime, while the second regime appears most likely to be related to structural changes in the copper surface.
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Hydrophobic surface efficiently boosting Cu 2O nanowires photoelectrochemical CO 2 reduction activity. Chem Commun (Camb) 2023; 59:5914-5917. [PMID: 37170969 DOI: 10.1039/d3cc00825h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The limited mass transfer of CO2 and the competitive hydrogen evolution reaction (HER) during photoelectrochemical (PEC) CO2 reduction usually result in low CO2 reduction activity. Here, we constructed a Cu2O/Sn/PTFE photocathode with a hydrophobic surface based on Cu2O by physical vapor deposition and a dipping method. The CO faradaic efficiency (FE) increased from 34.5% (Cu2O) to 95.1% (Cu2O/Sn/PTFE) at -0.7 V vs. RHE, and the FEH2 decreased from 27.9% (Cu2O) to 3.8% (Cu2O/Sn/PTFE). The introduction of the hydrophobic layer enhances the local CO2 concentration on the electrode surface and effectively isolates H+ from the aqueous electrolyte, thereby enhancing the CO2 reduction activity.
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9
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Unravelling the Effect of Activators used in The Synthesis of Biomass-Derived Carbon Electrocatalysts on the Electrocatalytic Performance for CO 2 Reduction. CHEMSUSCHEM 2023; 16:e202202188. [PMID: 36718877 DOI: 10.1002/cssc.202202188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 01/30/2023] [Accepted: 01/30/2023] [Indexed: 05/06/2023]
Abstract
N-doped carbon materials can be efficient and cost-effective catalysts for the electrochemical CO2 reduction reaction (CO2 RR). Activators are often used in the synthesis process to increase the specific surface area and porosity of these carbon materials. However, owing to the diversity of activators and the differences in physicochemical properties that these activators induce, the influence of activators used for the synthesis of N-doped carbon catalysts on their electrochemical performance is unclear. In this study, a series of bagasse-derived N-doped carbon catalysts is prepared with the assistance of different activators to understand the correlation between activators, physicochemical properties, and electrocatalytic performance for the CO2 RR. The properties of N-doped carbon catalysts, such as N-doping content, microstructure, and degree of graphitization, are found to be highly dependent on the type of activator applied in the synthesis procedure. Moreover, the overall CO2 RR performance of the synthesized electrocatalysts is not determined only by the N-doping level and the configuration of the N-dopant, but rather by the overall surface chemistry, where the porosity and the degree of graphitization are jointly responsible for significant differences in CO2 RR performance.
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10
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Gas-fed liquid-covered electrodes used for electrochemical reduction of dilute CO2 in a flue gas. J CO2 UTIL 2023. [DOI: 10.1016/j.jcou.2023.102472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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11
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Electrochemical conversion of CO2 to formic acid using a Sn based cathode: Combined effect of temperature and pressure. J CO2 UTIL 2023. [DOI: 10.1016/j.jcou.2022.102338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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12
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Investigation of the Structure of Atomically Dispersed NiN x Sites in Ni and N-Doped Carbon Electrocatalysts by 61Ni Mössbauer Spectroscopy and Simulations. J Am Chem Soc 2022; 144:21741-21750. [DOI: 10.1021/jacs.2c09825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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13
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Electrochemical reduction of CO 2 in the captured state using aqueous or nonaqueous amines. iScience 2022; 25:104558. [PMID: 35747389 PMCID: PMC9209719 DOI: 10.1016/j.isci.2022.104558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
CO2 capture and its electrochemical conversion have historically developed as two distinct technologies and scientific fields. Each process possesses unique energy penalties, inefficiencies, and costs, which accrue along the mitigation pathway from emissions to product. Recently, the concept of integrating CO2 capture and electrochemical conversion, or "electrochemically reactive capture," has aroused attention following early laboratory-scale proofs-of-concept. However, the integration of the two processes introduces new complexities at a basic science and engineering level, many of which have yet to be clearly defined. The key parameters to guide reaction, electrolyte, electrode, and system design would, therefore, benefit from delineation. To begin this effort, this perspective outlines several crucial physicochemical and electrochemical considerations, where we argue that the absence of basic knowledge leaves the field of designing metaphorically in the dark. The considerations make clear that there is ample need for fundamental science that can better inform design, following which the potential impacts of integration can be rigorously assessed beyond what is possible at present.
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14
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Benchmarking the Electrochemical CO
2
Reduction on Polycrystalline Copper Foils: The Importance of Microstructure Versus Applied Potential. ChemCatChem 2022. [DOI: 10.1002/cctc.202200540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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15
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The Effect of Temperature on the Cation‐Promoted Electrochemical CO
2
Reduction on Gold. ChemElectroChem 2022. [DOI: 10.1002/celc.202200239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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16
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Effects of the Catalyst Dynamic Changes and Influence of the Reaction Environment on the Performance of Electrochemical CO 2 Reduction. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2103900. [PMID: 34595773 DOI: 10.1002/adma.202103900] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Revised: 07/21/2021] [Indexed: 06/13/2023]
Abstract
Electrochemical reduction of carbon dioxide (CO2 ) is substantially researched due to its potential for storing intermittent renewable electricity and simultaneously helping mitigating the pressing CO2 emission concerns. The major challenge of electrochemical CO2 reduction lies on having good controls of this reaction due to its complicated reaction networks and its unusual sensitivity to the dynamic changes of the catalyst structure (chemical states, compositions, facets and morphology, etc.), and to the non-catalyst components at the electrode/electrolyte interface, in another word the reaction environments. To date, a comprehensive analysis on the interplays between the above catalyst-dynamic-changes/reaction environments and the CO2 reduction performance is rare, if not none. In this review, the catalyst dynamic changes observed during the catalysis are discussed based on the recent reports of electrochemical CO2 reduction. Then, the above dynamic changes are correlated to their effects on the catalytic performance. The influences of the reaction environments on the performance of CO2 reduction are also discussed. Finally, some perspectives on future investigations are offered with the aim of understanding the origins of the effects from the catalyst dynamic changes and the reaction environments, which will allow one to better control the CO2 reduction toward the desired products.
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17
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Probing dissolved CO 2(aq) in aqueous solutions for CO 2 electroreduction and storage. SCIENCE ADVANCES 2022; 8:eabo0399. [PMID: 35559679 PMCID: PMC9106293 DOI: 10.1126/sciadv.abo0399] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Accepted: 03/31/2022] [Indexed: 05/31/2023]
Abstract
CO2 dissolved in aqueous solutions CO2(aq) is important to CO2 capture, storage, photo-/electroreduction in the fight against global warming and to CO2 analysis in drinks. Here, we developed microscale infrared (IR) spectroscopy for in situ dynamic quantitating CO2(aq). The quantized CO2(g) rotational state transitions were observed to quench for CO2(aq), accompanied by increased H2O IR absorption. An accurate CO2 molar extinction coefficient ε was derived for in situ CO2(aq) quantification up to 58 atm. We directly measured CO2(aq) concentrations in electrolytes under CO2(g) bubbling and high-pressure conditions with high spectral and time resolutions. In KHCO3 electrolytes with CO2(aq) > ~1 M, CO2 electroreduction (CO2RR) to formate reached >98% Faradaic efficiencies on copper (Cu2O/Cu)-based electrocatalyst. Furthermore, CO2 dissolution/desolvation kinetics showed large hysteresis and ultraslow reversal of CO2(aq) supersaturation in aqueous systems, with implications to CO2 capture, storage, and supersaturation phenomena in natural water bodies.
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18
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Recent Advances in Interface Engineering for Electrocatalytic CO 2 Reduction Reaction. NANO-MICRO LETTERS 2021; 13:216. [PMID: 34694525 PMCID: PMC8545969 DOI: 10.1007/s40820-021-00738-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 09/13/2021] [Indexed: 05/13/2023]
Abstract
Electrocatalytic CO2 reduction reaction (CO2RR) can store and transform the intermittent renewable energy in the form of chemical energy for industrial production of chemicals and fuels, which can dramatically reduce CO2 emission and contribute to carbon-neutral cycle. Efficient electrocatalytic reduction of chemically inert CO2 is challenging from thermodynamic and kinetic points of view. Therefore, low-cost, highly efficient, and readily available electrocatalysts have been the focus for promoting the conversion of CO2. Very recently, interface engineering has been considered as a highly effective strategy to modulate the electrocatalytic performance through electronic and/or structural modulation, regulations of electron/proton/mass/intermediates, and the control of local reactant concentration, thereby achieving desirable reaction pathway, inhibiting competing hydrogen generation, breaking binding-energy scaling relations of intermediates, and promoting CO2 mass transfer. In this review, we aim to provide a comprehensive overview of current developments in interface engineering for CO2RR from both a theoretical and experimental standpoint, involving interfaces between metal and metal, metal and metal oxide, metal and nonmetal, metal oxide and metal oxide, organic molecules and inorganic materials, electrode and electrolyte, molecular catalysts and electrode, etc. Finally, the opportunities and challenges of interface engineering for CO2RR are proposed.
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19
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Chemical Modifications of Ag Catalyst Surfaces with Imidazolium Ionomers Modulate H 2 Evolution Rates during Electrochemical CO 2 Reduction. J Am Chem Soc 2021; 143:14712-14725. [PMID: 34472346 DOI: 10.1021/jacs.1c06212] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Bridging polymer design with catalyst surface science is a promising direction for tuning and optimizing electrochemical reactors that could impact long-term goals in energy and sustainability. Particularly, the interaction between inorganic catalyst surfaces and organic-based ionomers provides an avenue to both steer reaction selectivity and promote activity. Here, we studied the role of imidazolium-based ionomers for electrocatalytic CO2 reduction to CO (CO2R) on Ag surfaces and found that they produce no effect on CO2R activity yet strongly promote the competing hydrogen evolution reaction (HER). By examining the dependence of HER and CO2R rates on concentrations of CO2 and HCO3-, we developed a kinetic model that attributes HER promotion to intrinsic promotion of HCO3- reduction by imidazolium ionomers. We also show that varying the ionomer structure by changing substituents on the imidazolium ring modulates the HER promotion. This ionomer-structure dependence was analyzed via Taft steric parameters and density functional theory calculations, which suggest that steric bulk from functionalities on the imidazolium ring reduces access of the ionomer to both HCO3- and the Ag surface, thus limiting the promotional effect. Our results help develop design rules for ionomer-catalyst interactions in CO2R and motivate further work into precisely uncovering the interplay between primary and secondary coordination in determining electrocatalytic behavior.
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20
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Tandem Electrocatalytic CO 2 Reduction with Efficient Intermediate Conversion over Pyramid-Textured Cu-Ag Catalysts. ACS APPLIED MATERIALS & INTERFACES 2021; 13:40513-40521. [PMID: 34405982 DOI: 10.1021/acsami.1c08688] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
If combined with renewably generated electricity, electrochemical CO2 reduction (E-CO2R) could be used as a sustainable source of chemicals and fuels. Tandem catalysis approaches are attractive for providing the product selectivity, which would be required for commercial applications. Here, we demonstrate a two-step tandem electrocatalytic E-CO2R with efficient conversion of the intermediate species. The catalyst scaffold is Si(100), which is etched to form a textured surface consisting of micron-sized pyramid structures with the {111} facets. Two metals are used in the electrocatalytic cascade: Ag is employed to perform a two-electron reduction of CO2 to the intermediate CO, and Cu performs conversion to more reduced products. Using high-angle physical vapor deposition, we form separated, micron-scale areas of the two electrocatalysts on opposite sides of the pyramids, with their relative surface coverages being tunable with the deposition angle. Compared to the textured scaffolds with blanket Ag and Cu used as controls, bimetallic pyramid tandem catalysts have higher current densities and much lower faradic efficiencies (FE) for CO. These effects are due to efficient conversion of the CO formed on Ag to more reduced products on Cu. Methane is the main product to be enhanced by the cascade pathway: a bimetallic catalyst with approximately equal coverages of Ag and Cu produces methane with a FE of 62% at -1.1 VRHE, corresponding to a partial current density of 12.7 mA cm-2. We estimate an intermediate conversion yield for the CO intermediate of 80-90%, which is close to the mass-transport limited value predicted by reaction-diffusion simulations.
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21
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A selective polypyrrole-based sub-ppm impedimetric sensor for the detection of dissolved hydrogen sulfide and ammonia in a mixture. JOURNAL OF HAZARDOUS MATERIALS 2021; 416:125892. [PMID: 34492830 DOI: 10.1016/j.jhazmat.2021.125892] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 04/03/2021] [Accepted: 04/09/2021] [Indexed: 06/13/2023]
Abstract
An impedance-transducer sensor was developed for in situ detection of hydrogen sulfide (H2S) and ammonia (NH3) in aqueous media. Using cyclic voltammetry (CV), polypyrrole (PPy) was deposited on the surface of the microfabricated interdigitated gold electrode. Due to the proton acid doping effect of H2S on PPy and ionic conduction of the film, the sensor showed a decreasing impedance response to H2S unlike other reducing chemicals, i.e., ammonia (NH3). The recorded faradaic data was then associated with an equivalent circuit and compared with that of NH3 to examine the selectivity of the sensor. An electrochemical impedance spectroscopy (EIS) analysis was applied to the mixture of H2S and NH3 prepared at different ratios for the concentrations ranging from 2 ppm to 20 ppm (below 2-ppm, no response was observed due to the formation of NH4HS, not sensible with PPy). The principal component analysis (PCA) was used to train a real-time prediction model for both classification (for the type of the analyte) and regression (the concentration of the analyte). The results showed the high performance of the sensor in determining individual analytes while the model was able to accurately predict the amount of H2S and NH3 in the mixture.
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22
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Approaching 100% Selectivity at Low Potential on Ag for Electrochemical CO 2 Reduction to CO Using a Surface Additive. ACS Catal 2021. [DOI: 10.1021/acscatal.1c00830] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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23
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Recent Advances in Carbon Dioxide Conversion: A Circular Bioeconomy Perspective. SUSTAINABILITY 2021. [DOI: 10.3390/su13126962] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Managing the concentration of atmospheric CO2 requires a multifaceted engineering strategy, which remains a highly challenging task. Reducing atmospheric CO2 (CO2R) by converting it to value-added chemicals in a carbon neutral footprint manner must be the ultimate goal. The latest progress in CO2R through either abiotic (artificial catalysts) or biotic (natural enzymes) processes is reviewed herein. Abiotic CO2R can be conducted in the aqueous phase that usually leads to the formation of a mixture of CO, formic acid, and hydrogen. By contrast, a wide spectrum of hydrocarbon species is often observed by abiotic CO2R in the gaseous phase. On the other hand, biotic CO2R is often conducted in the aqueous phase and a wide spectrum of value-added chemicals are obtained. Key to the success of the abiotic process is understanding the surface chemistry of catalysts, which significantly governs the reactivity and selectivity of CO2R. However, in biotic CO2R, operation conditions and reactor design are crucial to reaching a neutral carbon footprint. Future research needs to look toward neutral or even negative carbon footprint CO2R processes. Having a deep insight into the scientific and technological aspect of both abiotic and biotic CO2R would advance in designing efficient catalysts and microalgae farming systems. Integrating the abiotic and biotic CO2R such as microbial fuel cells further diversifies the spectrum of CO2R.
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24
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Electrolyte Effects on the Faradaic Efficiency of CO 2 Reduction to CO on a Gold Electrode. ACS Catal 2021; 11:4936-4945. [PMID: 34055454 PMCID: PMC8154322 DOI: 10.1021/acscatal.1c00272] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/24/2021] [Indexed: 01/26/2023]
Abstract
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The electrochemical
reduction of CO2 aims to be a central
technology to store excess electricity generated by wind and solar
energy. However, the reaction is hindered by the competition with
the hydrogen evolution reaction. In this paper, we present a detailed
quantitative study of the Faradaic efficiency (FE) to CO on a gold
electrode under well-defined mass-transport conditions using rotating
ring-disk electrode voltammetry. Varying the concentration of the
bicarbonate and the electrolyte cation employing different rotation
rates, we map out how these parameters affect the FE(CO). We identify
two different potential regimes for the electrolyte effects, characterized
by a different dependence on the cation and bicarbonate concentrations.
For hydrogen evolution, we analyze the nature of the proton donor
for an increasingly negative potential, showing how it changes from
carbonic acid to bicarbonate and to water. Our study gives detailed
insights into the role of electrolyte composition and mass transport,
and helps defining optimized electrolyte conditions for a high FE(CO).
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Process Parameters in the Electrochemical Reduction of Carbon Dioxide to Ethylene. CHEMBIOENG REVIEWS 2021. [DOI: 10.1002/cben.202100004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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26
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Fundamentals, On-Going Advances and Challenges of Electrochemical Carbon Dioxide Reduction. ELECTROCHEM ENERGY R 2021. [DOI: 10.1007/s41918-021-00096-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Operando cathode activation with alkali metal cations for high current density operation of water-fed zero-gap carbon dioxide electrolyzers. NATURE ENERGY 2021; 6:439-448. [PMID: 33898057 PMCID: PMC7610664 DOI: 10.1038/s41560-021-00813-w] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 03/08/2021] [Indexed: 05/04/2023]
Abstract
Continuous-flow electrolyzers allow CO2 reduction at industrially relevant rates, but long-term operation is still challenging. One reason for this is the formation of precipitates in the porous cathode from the alkaline electrolyte and the CO2 feed. Here we show that while precipitate formation is detrimental for the long-term stability, the presence of alkali metal cations at the cathode improves performance. To overcome this contradiction, we develop an operando activation and regeneration process, where the cathode of a zero-gap electrolyzer cell is periodically infused with alkali cation-containing solutions. This enables deionized water-fed electrolyzers to operate at a CO2 reduction rate matching that of those using alkaline electrolytes (CO partial current density of 420 ± 50 mA cm-2 for over 200 hours). We deconvolute the complex effects of activation and validate the concept with five different electrolytes and three different commercial membranes. Finally, we demonstrate the scalability of this approach on a multi-cell electrolyzer stack, with a 100 cm2 / cell active area.
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Dramatic HER Suppression on Ag Electrodes via Molecular Films for Highly Selective CO2 to CO Reduction. ACS Catal 2021. [DOI: 10.1021/acscatal.1c00338] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Integrating CO 2 Capture with Electrochemical Conversion Using Amine-Based Capture Solvents as Electrolytes. Ind Eng Chem Res 2021. [DOI: 10.1021/acs.iecr.0c05848] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Copper sulfide as the cation exchange template for synthesis of bimetallic catalysts for CO 2 electroreduction. RSC Adv 2021; 11:23948-23959. [PMID: 35478999 PMCID: PMC9036827 DOI: 10.1039/d1ra03811g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 06/21/2021] [Indexed: 12/29/2022] Open
Abstract
Among metals used for CO2 electroreduction in water, Cu appears to be unique in its ability to produce C2+ products like ethylene. Bimetallic combinations of Cu with other metals have been investigated with the goal of steering selectivity via creating a tandem pathway through the CO intermediate or by changing the surface electronic structure. Here, we demonstrate a facile cation exchange method to synthesize Ag/Cu electrocatalysts for CO2 reduction using Cu sulfides as a growth template. Beginning with Cu2−xS nanosheets (C-nano-0, 100 nm lateral dimension, 14 nm thick), varying the Ag+ concentration in the exchange solution produces a gradual change in crystal structure from Cu7S4 to Ag2S, as the Ag/Cu mass ratio varies from 0.3 to 25 (CA-nano-x, x indicating increasing Ag fraction). After cation exchange, the nanosheet morphology remains but with increased shape distortion as the Ag fraction is increased. Interestingly, the control (C-nano-0) and cation exchanged nanosheets have very high faradaic efficiency for producing formate at low overpotential (−0.2 V vs. RHE). The primary effect of Ag incorporation is increased production of C2+ products at −1.0 V vs. RHE compared with C-nano-0, which primarily produces formate. Cation exchange can also be used to modify the surface of Cu foils. A two-step electro-oxidation/sulfurization process was used to form Cu sulfides on Cu foil (C-foil-x) to a depth of a few 10 s of microns. With lower Ag+ concentrations, cation exchange produces uniformly dispersed Ag; however, at higher concentrations, Ag particles nucleate on the surface. During CO2 electroreduction testing, the product distribution for Ag/Cu sulfides on Cu foil (CA-foil-x-y) changes in time with an initial increase in ethylene and methane production followed by a decrease as more H2 is produced. The catalysts undergo a morphology evolution towards a nest-like structure which could be responsible for the change in selectivity. For cation-exchanged nanosheets (CA-nano-x), pre-reduction at negative potentials increases the CO2 reduction selectivity compared to tests of as-synthesized material, although this led to the aggregation of nanosheets into filaments. Both types of bimetallic catalysts are capable of selective reduction of CO2 to multi-carbon products, although the optimal configurations appear to be metastable. Cu sulfides as a template for Ag/Cu sulfide catalysts for electrochemical CO2. With the introduction of Ag, nanosheet show increased C2+ product generation. The catalysts undergo a morphology evolution as CO2 reduction proceeds.![]()
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Facet-Dependent Selectivity of Cu Catalysts in Electrochemical CO 2 Reduction at Commercially Viable Current Densities. ACS Catal 2020; 10:4854-4862. [PMID: 32391186 PMCID: PMC7199425 DOI: 10.1021/acscatal.0c00297] [Citation(s) in RCA: 178] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 03/08/2020] [Indexed: 12/17/2022]
Abstract
![]()
Despite
substantial progress in the electrochemical conversion
of CO2 into value-added chemicals, the translation of fundamental
studies into commercially relevant conditions requires additional
efforts. Here, we study the catalytic properties of tailored Cu nanocatalysts
under commercially relevant current densities in a gas-fed flow cell.
We demonstrate that their facet-dependent selectivity is retained
in this device configuration with the advantage of further suppressing
hydrogen production and increasing the faradaic efficiencies toward
the CO2 reduction products compared to a conventional H-cell.
The combined catalyst and system effects result in state-of-the art
product selectivity at high current densities (in the range 100–300
mA/cm2) and at relatively low applied potential (as low
as −0.65 V vs RHE). Cu cubes reach an ethylene selectivity
of up to 57% with a corresponding mass activity of 700 mA/mg, and
Cu octahedra reach a methane selectivity of up to 51% with a corresponding
mass activity of 1.45 A/mg in 1 M KOH.
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Abstract
The photoelectrochemical CO2 reduction reaction (PEC-CO2RR) is a promising artificial photosynthetic system for storing solar energy as the energy of chemical bonds and stabilizing the atmospheric CO2 level. An applicable PEC-CO2RR is expected to have broad light absorption, high selectivity to a single product, and high solar to fuel efficiency. However, the PEC-CO2RR still faces challenges from complex reaction pathways, obstructed mass transfer, and large photovoltage requirements. The goal of this perspective is to point out some of the limitations of PEC-CO2RR to a practical application. In brief, we discuss the basic concepts of PEC-CO2RR and summarize state-of-the-art progress. Moreover, we highlight the remaining challenges to both science and engineering and propose the key steps in developing a fully functional PEC-CO2RR system. Finally, an ideal PEC-CO2RR system is proposed for future studies, which is essentially wireless and combines the advantages of minimized polarization loss and broad light absorption.
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Rational Design of Ion Exchange Membrane Material Properties Limits the Crossover of CO 2 Reduction Products in Artificial Photosynthesis Devices. ACS APPLIED MATERIALS & INTERFACES 2020; 12:12030-12042. [PMID: 32013387 DOI: 10.1021/acsami.9b21415] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Efficient operation is crucial for the deployment of photoelectrochemical CO2 reduction devices for large-scale artificial photosynthesis. In these devices, undesired transport of CO2 reduction products from the reduction electrode to the oxidation electrode may occur through a liquid electrolyte and an ion exchange membrane, reducing device productivity and increasing the energy required for product purification. Our work investigated the CO2 reduction product crossover through ion exchange membranes separating the cathode and anode compartments in CO2 reduction cells. The concentrations of liquid products produced by CO2 reduction on copper foil were measured. A systematic approach for the investigation of product crossover was developed. The crossover of products was analyzed over a range of working electrode potentials (-1.08 V vs RHE to -0.88 V vs RHE) in cells employing a commercial Selemion AMV membrane and a new poly(vinylimidazolium) family of ion exchange membranes with variable chemical and structural properties. We found that product loss due to electromigration of charged species in the device was more significant than product loss due to diffusion of uncharged species. To reduce the crossover of CO2 reduction products, the influence of membrane properties such as the ionic conductivity and water volume fraction was investigated for the Selemion AMV membrane and poly(vinylimidazolium) membranes with variable material properties. We show that the water volume fraction and, by extension, ionic conductivity of the membrane may be controlled to reduce product crossover in CO2 reduction artificial photosynthesis devices.
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Extraction of bubble size and number data from an acoustically-excited bubble chain. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 147:921. [PMID: 32113302 DOI: 10.1121/10.0000488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 12/01/2019] [Indexed: 06/10/2023]
Abstract
The passive-acoustic measurement of bubbly flows could potentially deliver data useful to many industrial and environmental applications. However, acoustic interactions between bubbles complicate interpretations of measured frequencies in terms of the bubble sizes that are of practical interest. Experiments were undertaken on the emissions of a bubble chain when a just-formed bubble at one end of the chain created a sound pulse. This is an idealised paradigm for many applications. The chain was a one-dimensional line of bubbles fixed with known bubble sizes and inter-bubble spacings. Frequencies naturally emitted by the chain were measured for various bubble sizes and spacings, including cases such that the bubbles were close to touching. Semi-empirical fits were found relating the bubble size and number to the lowest and highest-measurable peak frequencies. It was found that all data collapsed onto two curves, one for the lowest-peak and one for the highest-peak frequency. This was confirmed by running numerical simulations for wider ranges of parameters than available experimentally. The results suggest that for a bubble chain, measurements of two peak frequencies could be used to determine the bubble size and also the number of interacting bubbles.
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35
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Investigating Electrode Flooding in a Flowing Electrolyte, Gas-Fed Carbon Dioxide Electrolyzer. CHEMSUSCHEM 2020; 13:400-411. [PMID: 31736202 DOI: 10.1002/cssc.201902547] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 10/29/2019] [Indexed: 05/08/2023]
Abstract
Managing the gas-liquid interface within gas-diffusion electrodes (GDEs) is key to maintaining high product selectivities in carbon dioxide electroreduction. By screening silver-catalyzed GDEs over a range of applied current densities, an inverse correlation was observed between carbon monoxide selectivity and the electrochemical double-layer capacitance, a proxy for wetted electrode area. Plotting current-dependent performance as a function of cumulative charge led to data collapse onto a single sigmoidal curve indicating that the passage of faradaic current accelerates flooding. It was hypothesized that high cathode alkalinity, driven by both initial electrolyte conditions and cathode half-reactions, promotes carbonate formation and precipitation which, in turn, facilitates electrolyte permeation. This mechanism was reinforced by the observations that post-test GDEs retain less hydrophobicity than pristine materials and that water-rinsing and drying electrodes temporarily recovers peak selectivity. This knowledge offers an opportunity to design electrodes with greater carbonation tolerance to improve device longevity.
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36
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Host-Guest Chemistry Meets Electrocatalysis: Cucurbit[6]uril on a Au Surface as a Hybrid System in CO 2 Reduction. ACS Catal 2020; 10:751-761. [PMID: 31929948 PMCID: PMC6945685 DOI: 10.1021/acscatal.9b04221] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/18/2019] [Indexed: 12/18/2022]
Abstract
![]()
The rational control of forming and stabilizing reaction
intermediates
to guide specific reaction pathways remains to be a major challenge
in electrocatalysis. In this work, we report a surface active-site
engineering approach for modulating electrocatalytic CO2 reduction using the macrocycle cucurbit[6]uril (CB[6]). A pristine
gold surface functionalized with CB[6] nanocavities was studied as
a hybrid organic–inorganic model system that utilizes host–guest
chemistry to influence the heterogeneous electrocatalytic reaction.
The combination of surface-enhanced infrared absorption (SEIRA) spectroscopy
and electrocatalytic experiments in conjunction with theoretical calculations
supports capture and reduction of CO2 inside the hydrophobic
cavity of CB[6] on the gold surface in aqueous KHCO3 at
negative potentials. SEIRA spectroscopic experiments show that the
decoration of gold with the supramolecular host CB[6] leads to an
increased local CO2 concentration close to the metal interface.
Electrocatalytic CO2 reduction on a CB[6]-coated gold electrode
indicates differences in the specific interactions between CO2 reduction intermediates within and outside the CB[6] molecular
cavity, illustrated by a decrease in current density from CO generation,
but almost invariant H2 production compared to unfunctionalized
gold. The presented methodology and mechanistic insight can guide
future design of molecularly engineered catalytic environments through
interfacial host–guest chemistry.
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Abstract
The electrochemical reduction of CO2 stores intermittent renewable energy in valuable raw materials, such as chemicals and transportation fuels, while minimizing carbon emissions and promoting carbon-neutral cycles. Recent technoeconomic reports suggested economically feasible target products of CO2 electroreduction and the relative influence of key performance parameters such as faradaic efficiency (FE), current density, and overpotential in the practical industrial-scale applications. Furthermore, fundamental factors, such as available reaction pathways, shared intermediates, competing hydrogen evolution reaction, scaling relations of the intermediate binding energies, and CO2 mass transport limitations, should be considered in relation to the electrochemical CO2 reduction performance. Intensive research efforts have been devoted to designing and developing advanced electrocatalysts and improving mechanistic understanding. More recently, the research focus was extended to the catalyst environment, because the interfacial region can delicately modulate the catalytic activity and provide effective solutions to challenges that were not fully addressed in the material development studies. Herein, we discuss the importance of catalyst-electrolyte interfaces in improving key operational parameters based on kinetic equations. Furthermore, we extensively review previous studies on controlling organic modulators, electrolyte ions, electrode structures, as well as the three-phase boundary at the catalyst-electrolyte interface. The interfacial region modulates the electrocatalytic properties via electronic modification, intermediate stabilization, proton delivery regulation, catalyst structure modification, reactant concentration control, and mass transport regulation. We discuss the current understanding of the catalyst-electrolyte interface and its effect on the CO2 electroreduction activity.
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39
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40
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On the Oxidation State of Cu 2 O upon Electrochemical CO 2 Reduction: An XPS Study. Chemphyschem 2019; 20:3120-3127. [PMID: 31310028 DOI: 10.1002/cphc.201900468] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 07/15/2019] [Indexed: 01/10/2023]
Abstract
The encouraging selectivity of copper oxides for the electroreduction of CO2 into ethylene and alcohols has led to a vivid debate on the possible relation between their operando (sub-)surface oxidation state (i. e. fully reduced or partially oxidized) and this distinct reactivity. The high roughness of the Cu oxides used in previous studies on this matter adds complexity to this controversy and motivated us to prepare quasi-planar Cu2 O thin films that displayed a CO2 reduction selectivity similar to that of oxide-derived copper catalysts reported in previous studies. Most importantly, when the post-mortem thin films were transferred for characterization in an air-free environment, X-ray photoelectron spectroscopy measurements confirmed their complete reduction in the course of the CO2 reduction reaction. Thus, our results indicate that the selectivity of the Cu oxides featured in previous studies stems from their enhanced roughness, highlighting the importance of controlled sample transfer upon post-mortem characterization with ex situ techniques.
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41
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In‐Situ Nanostructuring and Stabilization of Polycrystalline Copper by an Organic Salt Additive Promotes Electrocatalytic CO
2
Reduction to Ethylene. Angew Chem Int Ed Engl 2019; 58:16952-16958. [DOI: 10.1002/anie.201907935] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/13/2019] [Indexed: 01/02/2023]
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42
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In‐Situ Nanostructuring and Stabilization of Polycrystalline Copper by an Organic Salt Additive Promotes Electrocatalytic CO
2
Reduction to Ethylene. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201907935] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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44
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In Situ Infrared Spectroscopy Reveals Persistent Alkalinity near Electrode Surfaces during CO 2 Electroreduction. J Am Chem Soc 2019; 141:15891-15900. [PMID: 31523949 PMCID: PMC6788196 DOI: 10.1021/jacs.9b07000] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
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Over
the past decade, electrochemical carbon dioxide reduction
has become a thriving area of research with the aim of converting
electricity to renewable chemicals and fuels. Recent advances through
catalyst development have significantly improved selectivity and activity.
However, drawing potential dependent structure–activity relationships
has been complicated, not only due to the ill-defined and intricate
morphological and mesoscopic structure of electrocatalysts, but also
by immense concentration gradients existing between the electrode
surface and bulk solution. In this work, by using in situ surface
enhanced infrared absorption spectroscopy (SEIRAS) and computational
modeling, we explicitly show that commonly used strong phosphate buffers
cannot sustain the interfacial pH during CO2 electroreduction
on copper electrodes at relatively low current densities, <10 mA/cm2. The pH near the electrode surface was observed to be as
much as 5 pH units higher compared to bulk solution in 0.2 M phosphate
buffer at potentials relevant to the formation of hydrocarbons (−1
V vs RHE), even on smooth polycrystalline copper electrodes. Drastically
increasing the buffer capacity did not stand out as a viable solution
for the problem as the concurrent production of hydrogen increased
dramatically, which resulted in a breakdown of the buffer in a narrow
potential range. These unforeseen results imply that most of the studies,
if not all, on electrochemical CO2 reduction to hydrocarbons
in CO2 saturated aqueous solutions were evaluated under
mass transport limitations on copper electrodes. We underscore that
the large concentration gradients on electrodes with high local current
density (e.g., nanostructured) have important implications on the
selectivity, activity, and kinetic analysis, and any attempt to draw
structure–activity relationships must rule out mass transport
effects.
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In-Situ Infrared Spectroscopy Applied to the Study of the Electrocatalytic Reduction of CO 2 : Theory, Practice and Challenges. Chemphyschem 2019; 20:2904-2925. [PMID: 31441195 DOI: 10.1002/cphc.201900533] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Revised: 08/22/2019] [Indexed: 11/11/2022]
Abstract
The field of electrochemical CO2 conversion is undergoing significant growth in terms of the number of publications and worldwide research groups involved. Despite improvements of the catalytic performance, the complex reaction mechanisms and solution chemistry of CO2 have resulted in a considerable amount of discrepancies between theoretical and experimental studies. A clear identification of the reaction mechanism and the catalytic sites are of key importance in order to allow for a qualitative breakthrough and, from an experimental perspective, calls for the use of in-situ or operando spectroscopic techniques. In-situ infrared spectroscopy can provide information on the nature of intermediate species and products in real time and, in some cases, with relatively high time resolution. In this contribution, we review key theoretical aspects of infrared reflection spectroscopy, followed by considerations of practical implementation. Finally, recent applications to the electrocatalytic reduction of CO2 are reviewed, including challenges associated with the detection of reaction intermediates.
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46
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Atomic Layer Deposition of ZnO on CuO Enables Selective and Efficient Electroreduction of Carbon Dioxide to Liquid Fuels. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201909610] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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47
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Atomic Layer Deposition of ZnO on CuO Enables Selective and Efficient Electroreduction of Carbon Dioxide to Liquid Fuels. Angew Chem Int Ed Engl 2019; 58:15036-15040. [DOI: 10.1002/anie.201909610] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Indexed: 11/10/2022]
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48
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Nanocrystal/Metal–Organic Framework Hybrids as Electrocatalytic Platforms for CO
2
Conversion. Angew Chem Int Ed Engl 2019; 58:12632-12639. [DOI: 10.1002/anie.201905172] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/19/2019] [Indexed: 11/08/2022]
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49
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Nanocrystal/Metal–Organic Framework Hybrids as Electrocatalytic Platforms for CO
2
Conversion. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201905172] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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50
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Investigating the Nature of the Active Sites for the CO2 Reduction Reaction on Carbon-Based Electrocatalysts. ACS Catal 2019. [DOI: 10.1021/acscatal.9b01513] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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