Electrochemical Carbon Dioxide Research Articles

Electronic interactions between SnO2 crystals and porous N-doped carbon nanoflowers accelerate electrochemical reduction of CO2 to formate

The electrochemical carbon dioxide reduction reaction (CO2RR) to formic acid or formate is a highly effective approach for achieving carbon neutrality. However, multiple proton-coupling-electronic processes and the instability of the catalysts caused by surface poisoning greatly limit the overall efficiency of CO2RR to formate. Here, a facile method was developed to anchor ∼2.60 nm SnO2 crystals onto porous N-doped carbon nanoflowers (SnO2@N-GPC) for high-efficiency formate production. The maximum Faraday efficiency (FE) of the SnO2@N-GPC reached 96.3 % at −1.2 V vs reversible hydrogen electrode (RHE) and was more than 80.0 % in the potential region from −1.0 to −1.5 V vs RHE with ten hours of operating stability. The experimental results and density functional theory (DFT) calculations demonstrated that the electronic interactions between SnO2 and N-GPC precipitated by electron transfer from SnO2 to N-GPC at the interface improved the phase stability of the SnO2@N-GPC, which improved its stability for the CO2RR. Furthermore, the electronic interactions enhanced the adsorption of CO2 on the catalyst, accelerating the rate of the formation of key intermediates, and reducing the energy barrier of the rate-limiting step for generating formate. This study provides an efficient strategy for developing highly active and stable non-precious metal catalysts for the conversion of CO2 to high-value chemicals.

Construction of Interlayered Single-Atom Active Sites on Bipyridine-Based 2D Conjugated Covalent-Organic Frameworks for Boosting the C2 Products of Electrochemical CO2 Reduction.

The electrochemical carbon dioxide reduction (eCO2RR) shows great potential in the realization of carbon neutrality, which requires a dedicated catalyst design. To develop electrocatalysts that favor C2 products, herein, the synthetic protocol for engineering interlayered single-atom metal active sites on the bipyridine-linked 2D conjugated covalent-organic framework (2D c-COF) has been developed by utilizing the interlayer π-π stacking. The resultant M@BTT-BPy-COF (where M = Cu, Ni, and Fe) provides fully exposed single-atom active sites with a suitable interdistance for catalyzing the key C-C coupling in the eCO2RR process. The Faradaic efficiency of ethanol (FEethanol) exceeds 40% with M@BTT-BPy-COF at -0.8 V vs RHE, outperforming most reported COF-based electrocatalysts. Density functional calculations suggest that the proximal active sites in the pore channel of COFs are the key active sites for promoting the C-C coupling to generate ethanol product. This investigation presents a novel way to engineer single-atom catalytic centers on 2D c-COFs, displaying the great potential of 2D c-COFs in electrocatalysis.

Hydrophilic Separator Stables CO2-to-C2H4 Conversion at Low Cell Voltage with Non-Noble Metal Anode

Electrochemical carbon dioxide (CO2) reduction (ECR) is a promising approach for enabling the conversion of greenhouse gas CO2 into valuable products with electricity from renewable sources to achieve net-zero CO2 emission. ECR simultaneously reduces carbon emissions and dependence on fossil-based fuels and chemicals. Membrane electrode assemblies (MEAs), which often comprise an anion exchange membrane (AEM) and a precious iridium oxide (IrOx)-based anode, have been extensively studied in the last few years. However, challenges such as salt precipitation on cathodic gas diffusion electrodes (GDEs), high cell voltage and the need to use noble metal anodes have hindered ECR's practical applications. Herein, we introduce a new design of MEA cells using a low-cost hydrophilic film separator and a Nickel (Ni) foam instead of AEM and IrOx, respectively. Hydrophilic separator material with high water permeability lowers the full-cell voltage and eliminates the salt accumulation on the GDE in both alkaline and neutral-pH conditions. Using copper-sputtered polytetrafluoroethylene (Cu/PTFE) as cathodes, we demonstrated a stable conversion of CO2 to ethylene (C2H4) at current densities over 100 mA/cm2. In neutral-pH anolyte, the average C2H4 FE was sustained at around 50% for more than 200 hours with a cell voltage of 3.1 V at the current density of 110 mA/cm2. Under alkaline conditions, this system showed 500 hours of stability of CO2-to-C2H4 conversion: the C2H4 FE was maintained above 60% with the cell voltage of only 2.2 V at 110 mA/cm2 current density. Our research provides a solution for achieving stable ECR operation at a relatively high current density using Earth-abundant materials. This work opens opportunities for energy-efficient and stable CO2 conversion without needing expensive and rare elements, which are crucial for practical applications.

Mesopore-Augmented Electrochemical CO2 Reduction on Nitrogen-Doped Carbon.

The electrochemical carbon dioxide reduction reaction (eCO2RR) using nitrogen-doped carbon (N-C) materials offers a promising and cost-effective approach to global carbon neutrality. Regulating the porosity of N-C materials can potentially increase the catalytic performance by suppressing the concurrence of the hydrogen evolution reaction (HER). However, the augmentation of porosity usually alters the active sites or the chemical composition of catalysts, resulting in intertwined influences of various structural factors and catalytic performance. In this study, incorporating secondary carbon sources into the metal-organic framework (MOF) precursor through nanocasting aimed to selectively enhance the mesoporous structure, allowing for deciphering this effect from other changes in the catalyst composition. Consequently, the developed N-C catalyst exhibited a significant surface area with abundant mesopores, leading to a maximum Faradaic efficiency (FE)for carbon monoxide(CO)of 95% at -0.50 V versus the reversible hydrogen electrode (vs. RHE). Furthermore, the FE for CO is enhanced across a wide potential range, surpassing previously reported metal-free N-C eCO2RR catalysts. The investigation reveals that constructing mesoporous structures can induce excellent CO2 catalysis by enhancing the accessibility of active sites while establishing an elevated local pH at these sites.

Identification of Mass Transfer Mechanisms inside an Industrial Electrochemical Cell for CO2 to Formate Conversion through 2D Transient Modeling

Since the dawn of the industrial revolution, the Earth's atmosphere has experienced a gradual increase in carbon dioxide (CO2) concentrations, leading to the trapping of solar energy and consequent global warming. This shift in climate dynamics carries significant consequences, including heightened levels of secondary pollutants in urban areas and an increase in the frequency and severity of natural disasters. To address these pressing environmental challenges, there is a widespread global inclination toward adopting sustainable technologies and reducing CO2 and other greenhouse gas emissions [1,2]. However, the primary source of CO2 emissions remain the combustion of fossil fuels, which is expected to persist as the dominant energy source for the foreseeable future. It is driven by extensive usage across various sectors, notably in the chemical industry and transportation. Despite growing awareness of the need to curb greenhouse gas emissions, transitioning to viable alternatives in these sectors presents formidable challenges. Factors such as entrenched infrastructure, economic dependencies, and technological barriers complicate the shift away from fossil fuels, highlighting the complexity of the transition toward sustainable solutions [1,3]. The emergence of CO2 electrolyzers, which can be powered by various energy sources including renewable options like solar power, can redefine the production of chemicals, reducing our reliance on fossil fuels in this sector and thereby mitigating CO2 emissions. This shift offers a promising solution to address global warming problems. These devices facilitate the conversion of CO2 into valuable chemicals through electrochemical processes, specifically the electrochemical CO2 Reduction Reaction (CO2RR), thus aiding emission reduction and integrating renewable energy into global infrastructure. However, scaling this technology to industrial levels reveals significant hurdles. Achieving consistent reaction rates across the whole cell's surface area, optimizing current distribution, and addressing challenges related to CO2 mass transfer are critical considerations. Among these challenges, maintaining electrochemical performance over time emerges as the most important factor. Industrial-scale implementation is further complicated by the inherent complexity of operational modes, expanded surface areas, and intricate flow paths. Consequently, adopting a model-based approach becomes paramount. Leveraging computational models allows for comprehensive analysis and optimization of large-scale CO2 electrolysis systems, helping to understand system dynamics and to refine pivotal components such as gas diffusion electrodes. Advancing CO2 electrolyzer technology holds significant importance for both academic research and industrial applications in the pursuit of sustainable energy solutions [4,5]. In this study, we present a two-dimensional transient-state multiphase Gas Diffusion Electrode (GDE) model, which describes mass and heat transfer, electrochemical kinetics, aqueous-phase reactions, and species concentrations within the total flowing electrolyte volume in the system over time. Our study focuses on the conversion of CO2 to formate due to its industrial significance and commercial viability. We provide experimental validation of the model using results obtained from an industrial cell, specifically the first industrial 1526 cm² electrochemical cell. This represents a significant advancement, with a 60-fold increase from the largest three-compartment electrolyzer reported to date [6]. Subsequently, we apply the model to predict the scalability of the GDE and assess the impact of key parameters on system performance. We observe that electrolyzers with greater heights exhibit significantly stronger reactions at the same current density. Moreover, the model effectively captures the pH time dependency at various points in the GDE and aids in identifying the stability and evolution of the chemical species composing the GDE. It also accurately represents variations in carbonate and bicarbonate production, as well as the decrease of hydroxide over time in the catholyte. Furthermore, in the context of stability, we numerically investigate the impact of catalyst degradation over time on system performance. [1] Konderla, Vojtěch. "Numerical modelling of a gas diffusion-based CO2 electrolyser with flowing catholyte." (2022). [3] Kibria, Md Golam, et al. "Electrochemical CO2 reduction into chemical feedstocks: from mechanistic electrocatalysis models to system design." Advanced Materials 31.31 (2019): 1807166. [3] Smith, Wilson A., et al. "Pathways to industrial-scale fuel out of thin air from CO2 electrolysis." Joule 3.8 (2019): 1822-1834. [4] Yang, Ziming, et al. "Modeling and upscaling analysis of gas diffusion electrode-based electrochemical carbon dioxide reduction systems." ACS Sustainable Chemistry & Engineering 9.1 (2020): 351-361. [5] Gawel, A., et al., Electrochemical CO2 reduction-the macroscopic world of electrode design, reactor concepts & economic aspects. IScience, 2022. [6] Fink, A.G., et al., Scale‐up of Electrochemical Flow Cell towards Industrial CO2 Reduction to Potassium Formate. ChemCatChem: p. e202300977. Figure 1

Solid-State Electrochemical Carbon Dioxide Capture by Conductive Metal-Organic Framework Incorporating Nickel Bis(diimine) Units.

This paper presents the first implementation of electrically conductive metal-organic framework (MOF) Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2) integrated with nickel bis(diimine) (Ni-BDI) units for efficient solid-state electrochemical carbon dioxide (CO2) capture. The electrochemical cell assembled using Ni3(HITP)2 as working electrodes can reversibly capture and release CO2 through potential control. A high-capacity utilization of 96% and a Faraday efficiency of 98% have been achieved. The material also exhibits excellent electrochemical stability with its capacity maintained during 50 capture-release cycles and resistance to general interferences, including O2, H2O, NO2, and SO2. Capacity utilization of up to 35% is obtained at CO2 concentrations as low as 1%. The capture of CO2 at concentrations ranging from 1% to 100% requires exceptionally low energy consumption of only 30.5-72.4 kJ mol-1. Studies combining spectroscopic experiments and computational approaches reveal that the CO2 capture and release mechanism involves reversible carbamate formation on the N atom of the Ni-BDI unit in the MOF upon its one-electron redox reaction.

Engineering a Cu-Pd Paddle-Wheel Metal-Organic Framework for Selective CO2 Electroreduction.

Optimizing the binding energy between the intermediate and the active site is a key factor for tuning catalytic product selectivity and activity in the electrochemical carbon dioxide reduction reaction. Copper active sites are known to reduce CO2 to hydrocarbons and oxygenates, but suffer from poor product selectivity due to the moderate binding energies of several of the reaction intermediates. Here, we report an ion exchange strategy to construct Cu-Pd paddle wheel dimers within Cu-based metal-organic frameworks (MOFs), [Cu3-xPdx(BTC)2] (BTC=benzentricarboxylate), without altering the overall MOF structural properties. Compared to the pristine Cu MOF ([Cu3(BTC)2], HKUST-1), the Cu-Pd MOF shifts CO2 electroreduction products from diverse chemical species to selective CO generation. In situ X-ray absorption fine structure analysis of the catalyst oxidation state and local geometry, combined with theoretical calculations, reveal that the incorporation of Pd within the Cu-Pd paddle wheel node structure of the MOF promotes adsorption of the key intermediate COOH* at the Cu site. This permits CO-selective catalytic mechanisms and thus advances our understanding of the interplay between structure and activity toward electrochemical CO2 reduction using molecular catalysts.

Transition Metals Doped into g-C3N4 via N,O Coordination as Efficient Electrocatalysts for the Carbon Dioxide Reduction Reaction.

The electrochemical carbon dioxide reduction reaction (CO2RR) is a potential and efficient method that can directly convert CO2 into high-value-added chemicals under mild conditions. Owing to the exceptionally high activation barriers of CO2, catalysts play a pivotal role in CO2RR. In this study, the transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) is doped into g-C3N4 with a unique N,O-coordination environment, namely, TM-N1O2/g-C3N4. Herein, the catalytic performance and reaction mechanism for the CO2RR on TM-N1O2/g-C3N4 are systematically investigated by density functional theory methods. Especially, through the calculation of ΔG*H and ΔG*COOH/ΔG*OCHO, the catalysts with preference for the CO2RR over the hydrogen evolution reaction (HER) are selected for further study. Furthermore, Gibbs free energy computation results of each elementary step for the CO2RR on these catalysts indicate that Ti-N1O2/g-C3N4 has significant catalytic activity and selectivity for reducing CO2 to methanol (CH3OH) with the limiting potential (UL) of -0.55 V. Finally, through frontier molecular orbital theory and charge transfer analyses, the introduction of the O atoms illustrates that it is instrumental in regulating the electron distribution of the catalytic active site, thereby improving the catalytic performance. This work provides insight into the design of single-atom catalysts with unique coordination structures for the CO2RR.

Rational Strategies for Preparing Highly Efficient Tin-, Bismuth- or Indium-Based Electrocatalysts for Electrochemical CO2 Reduction to Formic acid/Formate.

Electrochemical carbon dioxide reduction reaction (CO2RR) is an environmentally friendly and economically viable approach to convert greenhouse gas CO2 into valuable chemical fuels and feedstocks. Among various products of CO2RR, formic acid/formate (HCOOH/HCOO-) is considered the most attractive one with its high energy density and ease of storage, thereby enabling widespread commercial applications in chemical, medicine, and energy-related industries. Nowadays, the development of efficient and financially feasible electrocatalysts with excellent selectivity and activity towards HCOOH/HCOO- is paramount for the industrial application of CO2RR technology, in which Tin (Sn), Bismuth (Bi), and Indium (In)-based electrocatalysts have drawn significant attention due to their high efficiency and various regulation strategies have been explored to design diverse advanced electrocatalysts. Herein, we comprehensively review the rational strategies to enhance electrocatalytic performances of these electrocatalysts for CO2RR to HCOOH/HCOO-. Specifically, the internal mechanism between the physicochemical properties of engineering materials and electrocatalytic performance is analyzed and discussed in details. Besides, the current challenges and future opportunities are proposed to provide inspiration for the development of more efficient electrocatalysts in this field.

Understanding the Electrochemical Carbon Dioxide Reduction Reaction Mechanism of Lattice Tuning of Copper by Silver Single-Crystal Surface.

Intermolecular interactions and adsorbate coverage on a metal electrode's surface/interface play an important role in CO2 reduction reaction (CO2RR). Herein, the activity and selectivity of CO2RR on bimetallic electrode, where a full monoatomic Cu layer covers on Ag surface (CuML/Ag) are investigated by using density functional theory calculations. The surface geometric and electronic structure results indicate that there is high electrocatalytic activity for CO2RR on the CuML/Ag electrode. Specifically, the CuML/Ag surface can accelerate the H2O and CO2 adsorption and hydrogenation while lowering the reaction energy of the rate-determining step. The structure parameters of chemisorbed CO2 with and without H2O demonstrate that activated H2O not only promotes the C-O dissociation but also provides the protons required for CO2RR on the CuML/Ag electrode surface. Furthermore, the various reaction mechanism diagrams indicate that the CuML/Ag electrode has high selectivity for CO2RR, and the efficiency of products can be regulated by modulating the reaction's electric potential.

Regulated Cu Diatomic Distance Promoting Carbon-Carbon Coupling During CO2 Electroreduction.

To address the bottle-neck carbon-carbon coupling issue during electrochemical carbon dioxide reduction (eCO2RR) to multicarbon (C2+) products, this work develops an anion-directed strategy (Cl-, NO3 -, and SO4 2-) to regulate interatomic distance of Cu diatoms. In comparison to pristine Cu (with a typical Cu-Cu distance of 2.53 Å), Cu-boroimidazole frameworks (BIF)/SO4, NO3, and Cl material shows elongated diatomic distance of 3.90 Å, 4.21 Å, and 3.30 Å, respectively. Among them, the Cu-BIF/Cl exhibits an outstanding eCO2RR performance with a Faradaic efficiency of 72.12% for C2+ products and an industrial-level current density of 539.0 mA cm-2 at -1.75 V versus RHE. Significantly, according to theoretical and in situ experimental investigation, the highly electronegative Cl- ion lifts d-band center of Cu sites of Cu-BIF/Cl, facilitating *CO adsorption with a low Gibbs free energy and its later dimerization overcoming a small energy barrier. In addition, this strategy to manipulate interatomic distance for diatomic catalysts, can also be adaptable to other reactions involving intermediate coupling and following the Langmuir-Hinshelwood mechanism, such as carbon-nitrogen coupling, nitrogen-nitrogen coupling, etc.

Dynamically Stabilizing Oxygen Atoms in Silver Catalyst for Highly Selective and Durable CO2 Reduction Reaction

AbstractOxide derived catalyst displays outstanding catalytic activity and selectivity in electrochemical carbon dioxide reduction reaction (CO2RR), in which, it is found that residue oxygen atoms play a pivotal role in regulating the catalyst's electronic structure and thus the CO2RR process. Unfortunately, the intrinsic thermodynamic instability of oxygen atoms in oxide derived catalyst under cathodic CO2RR potentials makes it unstable during continuous electrolysis, greatly hindering its practical industrial applications. In this work, we develop a pulsed‐bias technique that is able to dynamically stabilize the residue oxygen atoms in oxide derived catalyst during electrochemical CO2RR. As a result, the oxide derived catalyst under pulsed bias exhibits super catalytic stability in catalyzing electrochemical CO2RR, while keeping excellent catalytic activity and selectivity.

Experimental investigation of an integrated electro-cation exchange reactor for better carbon dioxide extraction and environmental management

The research focuses on a uniquely designed three-compartment type integrated electrochemical reactor developed in a laboratory setting. This innovative reactor uses an electrolytic cation exchange technique to extract substantial quantities of carbon dioxide from ocean water as bicarbonate and carbonate while simultaneously producing hydrogen gas for potential hydrocarbon production. The study employs the Design Expert software package to evaluate and optimize the implementation of electrochemical carbon dioxide extraction from ocean water. The reactor is divided into three compartments by two cation-exchange membranes: a middle part and two electrode parts for the cathode and anode sides. The membranes possess acidic properties that facilitate cation transport while inhibiting anion transport. The laboratory studies, including 35-minute long experimental runs, are conducted to determine the system's feasibility by assessing carbon dioxide extraction under different conditions, such as electrolyte concentration, applied voltage, and pH levels. The reactor achieves a maximum CO₂ extraction rate of 1479.73 mg/min, with optimal conditions yielding 1514.6 mg/min. The ideal operating parameters are found to be a voltage of 14.8 V, an electrolyte concentration of 0.557 M, and a pH of 2.26. The results of the optimization study further reveal that carbon dioxide extraction increases with decreasing pH levels.

Dynamically Stabilizing Oxygen Atoms in Silver Catalyst for Highly Selective and Durable CO2 Reduction Reaction.

Oxide derived catalyst displays outstanding catalytic activity and selectivity in electrochemical carbon dioxide reduction reaction (CO2RR), in which, it is found that residue oxygen atoms play a pivotal role in regulating the catalyst's electronic structure and thus the CO2RR process. Unfortunately, the intrinsic thermodynamic instability of oxygen atoms in oxide derived catalyst under cathodic CO2RR potentials makes it unstable during continuous electrolysis, greatly hindering its practical industrial applications. In this work, we develop a pulsed-bias technique that is able to dynamically stabilize the residue oxygen atoms in oxide derived catalyst during electrochemical CO2RR. As a result, the oxide derived catalyst under pulsed bias exhibits super catalytic stability in catalyzing electrochemical CO2RR, while keeping excellent catalytic activity and selectivity.

Harnessing in-situ oxidation of nanostructured mxene to modulate the electronic structure for improved selectivity for electrochemical carbon dioxide reduction

The electrochemical CO2 reduction reaction (CO2RR) is a promising approach to valorizing CO2. Ti3C2TX as a support material has received significant interest in enhancing CO2RR performance for tuning the electronic structure. However, there has been relatively less focus on changes to the Ti3C2TX electronic structure induced by loading catalysts onto the Ti3C2TX. Because Ti3C2TX has an intrinsic activity for both CO2RR and the competitive hydrogen evolution reaction (HER), electronic structure changes can affect the balance between CO2RR and HER selectivity. Therefore, tuning the electronic structure of Ti3C2TX can control the competition between CO2RR and HER and tune the selectivity and activity. Herein, we report that Ti3C2TX’s electronic structure can be tuned by the Ag+ loading method via redox interactions, tuning the reaction selectivity and activity for CO2RR. To illustrate this effect, we compare the CO2RR performance of in-situ formed Ag nanoparticles (NPs) on Ti3C2TX (0.9Ag-IS-Ti3C2TX) with physically mixed Ag NPs and Ti3C2TX (0.9Ag/P/Ti3C2TX). Here, ‘0.9’ refers to the molar ratio between Ag precursor and Ti3C2Tx, and ‘IS’ vs. ‘P’ refers to in-situ formed vs. physically mixed Ag NPs. 0.9Ag-IS-Ti3C2TX demonstrates a higher oxidation state for Ti and a higher proportion of Ti-O bonds than 0.9Ag/P/Ti3C2TX. Compared to 0.9Ag/P/Ti3C2TX, 0.9Ag-IS-Ti3C2TX exhibits higher CO Faradaic efficiency (FE), rising from 8.1 % with a partial current density of −2.0 mA cm−2 to 49.6 % with a partial current density of −20.1 mA cm−2 at −1.4 V vs. RHE (reversible hydrogen electrode). To harness this effect, we demonstrate control over the CO: H2 ratio of syngas formed from CO2RR over our Ti3C2TX-supported catalysts. Further electrochemical anodic oxidation experiments reveal the critical oxidation potential of Ti3C2TX (0.8 V vs. RHE) and show that HER can be partially suppressed by partial oxidation of Ti3C2TX. This work highlights the importance of considering the changes in Ti3C2TX (and other) supports when supporting catalysts for CO2RR and other electrochemical reactions.

Catalyst Design and Engineering for CO2-to-Formic Acid Electrosynthesis for a Low-Carbon Economy.

Formic acid (FA) has emerged as a promising candidate for hydrogen energy storage due to its favorable properties such as low toxicity, low flammability, and high volumetric hydrogen storage capacity under ambient conditions. Recent analyses have suggested that FA produced by electrochemical carbon dioxide (CO2) reduction reaction (eCO2RR) using low-carbon electricity exhibits lower fugitive hydrogen (H2) emissions and global warming potential (GWP) during the H2 carrier production, storage and transportation processes compared to those of other alternatives like methanol, methylcyclohexane, and ammonia. eCO2RR to FA can enable industrially relevant current densities without the need for high pressures, high temperatures, or auxiliary hydrogen sources. However, the widespread implementation of eCO2RR to FA is hindered by the requirement for highly stable and selective catalysts. Herein, the aim is to explore and evaluate the potential of catalyst engineering in designing stable and selective nanostructured catalysts that can facilitate economically viable production of FA.

Zirconium-doped ultrathin copper nanowires for C1 and C2+ products in electrochemical CO2 reduction reaction

Cu-based nanostructures have garnered significant attention in the field of electrochemical carbon dioxide reduction (eCO2R), due to their significant activity and ability to produce a variety of value-added hydrocarbons and oxygenates. Current research efforts focus on steering eCO2R towards the formation of multi-carbon (C2+) products and elucidating the complex mechanisms of C-C coupling. One promising approach involves transition metals into Cu nanostructures. This study computationally investigates the impact of trace Zr atom doping on Cu nanostructures, specifically at the interfaces of (100) and (110) surfaces of ultrathin Cu nanowires. Our findings reveal that Zr dopants are energetically favourable and facilitate charge transfer to adjacent Cu atoms, thereby reducing the activation barriers for C-C coupling and enhancing the formation of C1 and C2 hydrocarbons. Additionally, the Zr-O interaction weakens the C-O bond, promoting C-O bond cleavage. The formation of C3 products, and the selectivity between hydrocarbons and oxygenates, are influenced by the hydrogenation sequence on different carbon atoms.

Surface Area-Enhanced Cerium and Sulfur-Modified Hierarchical Bismuth Oxide Nanosheets for Electrochemical Carbon Dioxide Reduction to Formate.

Electrochemical carbon dioxide reduction reaction (ECO2RR) is a promising approach to synthesize fuels and value-added chemical feedstocks while reducing atmospheric CO2 levels. Here, high surface area cerium and sulfur-doped hierarchical bismuth oxide nanosheets (Ce@S-Bi2O3) are develpoed by a solvothermal method. The resulting Ce@S-Bi2O3 electrocatalyst shows a maximum formate Faradaic efficiency (FE) of 92.5% and a current density of 42.09mA cm-2 at -1.16V versus RHE using a traditional H-cell system. Furthermore, using a three-chamber gas diffusion electrode (GDE) reactor, a maximum formate FE of 85% is achieved in a wide range of applied potentials (-0.86 to -1.36V vs RHE) using Ce@S-Bi2O3. The density functional theory (DFT) results show that doping of Ce and S in Bi2O3 enhances formate production by weakening the OH* and H* species. Moreover, DFT calculations reveal that *OCHO is a dominant pathway on Ce@S-Bi2O3 that leads to efficient formate production. This study opens up new avenues for designing metal and element-doped electrocatalysts to improve the catalytic activity and selectivity for ECO2RR.

Enhancing formate yield through electrochemical CO2 reduction using BiOCl and g-C3N4 hybrid catalyst

Electrochemical carbon dioxide (CO2) reduction with bismuth-based catalysts has been widely investigated in the recent few years. This is due to bismuth’s ability to perform selective electrochemical CO2 reduction reaction (eCO2RR) to an important C1 product, the formate (HCOO–). However, boosting the performance of such catalysts is a continuous investigation. In this work, enhancing the active sites for eCO2RR is investigated by forming nanocomposites with graphitic carbon nitride (g-C3N4). BiOCl is synthesized by a simple wet-chemical approach in the presence of glycine as size-controlling agent and formed into nanocomposites, which were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Infrared (IR) Spectroscopy and N2 physisorption. Linear Sweep Voltammetry (LSV) in argon and CO2-saturated atmosphere showed higher current values in the case of CO2. Chronoamperometries (CA) were recorded at −1.06 V vs Reversible Hydrogen Electrode (RHE) for 5400 s obtaining Faradic Efficiencies (FE) varying in the range of 70–77 % depending on the nanocomposites’ composition. In fact, 52.1 wt% BiOCl/g-C3N4 formed the highest yields for formate (with also the highest rate of formation of formate) together with a minimal production of H2 and CO. The effect of nano-structuration induced by glycine, used as a size-controlling agent, to form nanoplates was crucial: microplates of BiOCl produced without glycine showed an FE of 4 %, reaching 85 % in the case of the nanoplates. Post-electrocatalysis characterization revealed the possible role of Bi2O2CO3 as the active phase for eCO2RR.

Customizing Ionic Liquids Functionalized MOFs Composites with Hydrophobic Interface for Electrochemical CO2 Reduction.

The electrochemical carbon dioxide reduction reaction (CO2RR) to generate feedstocks for chemical products (e.g., carbon monoxide, CO) offers a highly attractive method for achieving the closure of the carbon cycle. Ionic liquids (ILs)-functionalized Cu-based catalyst Cu2O-HKUST-1/IL1/PTFE was developed, configuring metal-organic frameworks(MOFs) based materials with high adsorption and multiple active sites. The modified electrocatalysts exhibited high specific surface area, strong CO2 adsorption capacity, abundant active sites, and fast charge transfer rate. The nucleophilic active site of deprotonation at the C2 site in imidazole ILs further improved the selectivity of proton migration and CO product generation, which was verified through DFT calculations for the low Gibbs free energy of the generated intermediate interactions. In addition, the hydrophobic interface constructed by PTFE facilitated the inhibition of the hydrogen evolution reaction (HER) and significantly improved the efficiency of CO2 electroreduction. The Cu2O-HKUST-1/IL1/PTFE catalyst manifested a high C1 Faraday efficiency (FE) up to 96.5% and in particular 92.7% for FECO at -1.7 V vs RHE. The present work provides an efficient strategy for configuring ILs-functionalized MOFs-based materials with good hydrophobic interfaces to enhance the efficiency of CO2 electroreduction to C1 products.