Co-electrolysis Of CO2 Research Articles

Life Cycle Assessment of CO2-Based and Conventional Methanol Production Pathways in Thailand

Methanol production through carbon capture and utilization technologies offers promising alternatives to traditional natural-gas-based methods, potentially mitigating climate change impacts and improving resource efficiency. This study evaluates four methanol production pathways: CO2 hydrogenation, tri-reforming of methane, electrochemical CO2 reduction, and co-electrolysis of CO2 and water. The analysis covers 19 scenarios, combining three electricity mixes (100% Thai grid mix, 50% Thai grid mix and 50% renewable energy, and 100% renewable energy) with two hydrogen production technologies (alkaline water electrolysis and grey hydrogen). Environmental life cycle assessment results showed that most pathways perform well when using the 100% renewable energy with co-electrolysis (CE-100%) showing the most substantial reductions across all impact categories as compared conventional methanol production. Electrochemical reduction demonstrated the poorest environmental performance for all scenarios. In Thailand, implementing the CE-100% pathway could potentially yield 12.4 million tonnes of methanol annually from the cement industry’s CO2 emissions, with an estimated value of approximately USD 5.4 billion, while reducing emissions from the industrial processes and product use (IPPU) sector by 75%. The findings provide valuable insights for policymakers, industry stakeholders, and researchers, supporting Thailand’s transition towards sustainable methanol production and broader climate goals.

Single-Atom Rh1 Alloyed Co for Urea Electrosynthesis from CO2 and NO3.

Single-atom Rh1 alloyed Co (Rh1Co) is explored as an efficient catalyst for urea electrosynthesis via coelectrolysis of CO2 and NO3- (UECN). Theoretical calculations and in situ spectroscopic measurements unravel the synergetic effect of Co and Rh1 in promoting the UECN process, where the Rh1 site activates NO3- to form *NH2, while the Co site activates CO2 to form *CO. The formed *CO then desorbs from the Co site and transfers to the Rh1 site, followed by continuous C-N coupling with *NH2 formed on the Rh1 site to synthesize urea. Remarkably, Rh1Co assembled in a flow cell delivers the exceptional urea yield rate of 24.9 mmol h-1 g-1 and Faradaic efficiency of 51.1%, outperforming most previously reported UECN catalysts.

(Energy Technology Division Supramaniam Srinivasan Young Investigator Award) CO2 as a Building Block for Electrosynthetic Coupling to N- and S- Based Reactants

Energy-intensive thermochemical processes within chemical manufacturing are a major contributor to global CO2 emissions. With the increasing push for sustainability, the scientific community is striving to develop renewable energy-powered electrochemical technologies in lieu of CO2-emitting fossil-fuel-driven methods. However, to fully electrify chemical manufacturing, it is imperative to expand the scope of electrosynthetic technologies, particularly through the innovation of reactions involving nitrogen- and sulfur- based reactants as products from water/CO2 electrolysis do not cover the full scope of industrial needs.To this end, this talk focuses on my lab’s efforts not only in CO2 conversion in the use of this molecule as a building block. This entails the co-electrolysis of CO2 with additional small molecule reactants (N2, NO3 -, SO3 2-...) in generating products with C-N and C-S bonds like amides, urea, and sulfonates that are important as commodity and fine chemicals in the chemical industry. In particular, I will discuss several new reaction pathways discovered towards several of the above-mentioned products and the application of operando techniques to understand the key C-N/C-S coupling steps in the reaction process. Figure 1

Spectroscopic Elucidation of Phase Evolution in NiO/YSZ Under Oxidative and Reductive Gas Environments

High temperature co-electrolysis of CO2 and H2O serves a viable, energy efficient, and scalable route to produce syngas (CO+ H2), which can be used to generate a variety of utility hydrocarbons. Solid oxide electrolysis cell (SOEC) has proven to be a promising technology for CO2 utilization and a carbon neutral route to curb CO2 emissions. The design of cathode catalyst is critical as it must facilitate the activation of CO2 and H2O and also exhibit high electronic and oxygen ion conductivity. The state-of-the-art cathode material used in SOECs is Ni/YSZ (8 mol% Yttria Stabilized Zirconia) ceramic composite (known as cermet), whose performance is dependent on various operating factors including temperature, composition of feed gas stream, presence of contaminants like SOx/NOx etc. There is a very limited number of studies on the evolution of the cathode materials under process level conditions. To begin with, effect of different oxidative and reductive gas environments and temperature over Ni/YSZ is studied using in situ Raman spectroscopy.Typical flue gas composition is chosen as the basis for the concentration of different components like 15% CO2, 10% H2O, 5% O2 with argon. Under oxidative conditions (O2, CO2, H2O) with temperature variation range of RT-800 0C, NiO/YSZ vibrational modes revealed that it is composed of NiO and YSZ phases. It is seen that there is thermal broadening in the bands of NiO and YSZ, thermal effects reversible upon cooling down and red shift in the NiO bands exemplified the lattice expansion. Exposing the NiO/YSZ to 5% H2 at high temperature resulted in the formation of metallic Ni, which is corroborated by the absence of the Ni-O vibrational modes in Raman spectrum at 400 0C. YSZ phase is quite stable in H2 at elevated temperature.After reduction of NiO/YSZ to get Ni/YSZ, exposure to oxidative environments (i.e., O2, CO2, H2O) aided in the formation of defect laden NiOx phase on YSZ. Specifically, NiOx formation starts at 350 0C under oxygen and at 450 0C under CO2 and H2O. Under 15% CO2, there is an overlap between the bands associated to the carbonate like species and the NiO phase but there is no formation of coke at these conditions as D and G bands were not observed (Fig. 1). It could be due to the oxidation of Ni that obliterated coke formation. The blue shift at 1046 cm-1 (2P mode of NiO) signifies the shortening of bond length in Ni-O with gradual conversion of Ni to NiOx. Compared to the NiOx phase formed under 5% O2 and 15% CO2 which has a sharp feature in Raman spectra, there is a broad band of NiOx phase formed under 10 % H2O in the region 480-580 cm-1 . This observation demonstrates the variation in the microcrystalline size of the defect laden NiOx phase formed under exposure to different oxidizers.Another set of experiments were done with the dry hydrogen (5 % H2) and humidified hydrogen (5% H2 + 10 % H2O) to study the role of presence of water on the reduction of NiO/YSZ with temperature variation between 120 – 800 0C. It was found that reduction of NiO to Ni is not affected by the presence of water. Under both conditions this transformation occurs between 400-600 0C. The results from the current study provide the key information on the effects of temperature and gas compositions over Ni/YSZ which serves as a guide for the process level design and operation of SOECs. References Juliana Carneiro et al, Industrial & Engineering Chemistry Research 2020 59(36), 15884-15893.John Kirtley et al, The Journal of Physical Chemistry C2013, 117 (49), 25908-25916.A. Naumenko et al, Phys Chem Solid State 2008, 9, 121–125. Figure 1

Lewis-base ligand-reshaped interfacial hydrogen-bond network boosts CO2 electrolysis.

Both the catalyst and electrolyte strongly impact the performance of CO2 electrolysis. Despite substantial progress in catalysts, it remains highly challenging to tailor electrolyte compositions and understand their functions at the catalyst interface. Here, we report that the ethylenediaminetetraacetic acid (EDTA) and its analogs, featuring strong Lewis acid-base interaction with metal cations, are selected as electrolyte additives to reshape the catalyst-electrolyte interface for promoting CO2 electrolysis. Mechanistic studies reveal that EDTA molecules are dynamically assembled toward interface regions in response to bias potential due to strong Lewis acid-base interaction of EDTA4--K+. As a result, the original hydrogen-bond network among interfacial H2O is disrupted, and a hydrogen-bond gap layer at the electrified interface is established. The EDTA-reshaped K+ solvation structure promotes the protonation of *CO2 to *COOH and suppressing *H2O dissociation to *H, thereby boosting the co-electrolysis of CO2 and H2O toward carbon-based products. In particular, when 5mM of EDTA is added into the electrolytes, the Faradaic efficiency of CO on the commercial Ag nanoparticle catalyst is increased from 57.0% to 90.0% at an industry-relevant current density of 500mA cm-2. More importantly, the Lewis-base ligand-reshaped interface allows a range of catalysts (Ag, Zn, Pd, Bi, Sn, and Cu) to deliver substantially increased selectivity of carbon-based products in both H-type and flow-type electrolysis cells.

Investigation of the kinetics of methanation of a post-coelectrolysis mixture on a Ni/CZP oxide catalyst

The use of synthetic natural gas (SNG) as a plug-and-play fuel coming from renewables can help to overcome the limitations given by the intermittency of renewable energy. A way to implement the production of SNG pass through the co-electrolysis of CO2 to a mixture of hydrogen, carbon monoxide and carbon dioxide, steam and small amounts of methane, followed by CO and CO2 methanation. The presence of different reactants and processes requires the comprehension and quantification of the kinetics of the reactions involved with the aim of optimizing methanation. In this work a kinetic model that considers both the direct CO2 methanation and the indirect RWGS + CO methanation pathways has been developed over a Ni(10 %wt)/Ce0.33Zr0.63Pr0.04O2. The kinetic study made it possible to understand the influence of the reactants and products on the reactions through the calculation of reaction rates. This allowed to test, by linearization, the models found in the literature and their adjustment permitted to calculate sixteen kinetic parameters (activation energies, heats of adsorption and pre-exponential factors) present in the rate laws of methanation of CO2, CO and the Reverse Water Gas Shift reaction. The models then made it possible to simulate the evolution of partial flow rates in an isothermal plug flow reactor and were compared to experimental data.

Efficient Energy Storage via Methane Production Using Protonic Ceramic Electrochemical Cells

Protonic ceramic electrochemical cells (PCECs) are promising energy storage technologies due to their high performance and ability to convert CO2 into value-added chemicals. However, there are many fundamental aspects of this technology that require investigation to better understand its interactions and opportunities. Thus, this paper focuses on the development of a steady-state PCEC model, encompassing intricate details of reactive porous-media transport, elementary catalytic chemistry, and electrochemistry within unit cells. The model is calibrated and validated using experimental data. The model presents the rate of methane production at different temperatures and revealed that efficient PCEC for co-electrolysis of CO2 and H2O is operated in the temperature range of 420–470 °C and the optimum being 450 °C at the rate of 0.0391 moldm−3 min−1. It provides insights into the effects of overpotentials on cell performance. At a current density of 3000 A/m2 the ohmic, concentration, and activation overpotentials amount to 0.65, 0.004, and 0.19 V, respectively. The results obtained from the model highlight the potential of PCECs as efficient CO2 sinks for decarbonization purposes and as a means of methane production. Furthermore, the model's findings offer valuable guidance for the design, selection of stacks, and choice of building materials in PCEC systems. The potential applications of PCECs as real-life fuel utilization technologies are justified with improved material development to reduce cell overpotentials, opening doors for scale-up and eventual commercialization. These findings contribute to the development of sustainable energy systems and advance the pursuit of decarbonization goals.

Solar fuels design: Porous cathodes modeling for electrochemical carbon dioxide reduction in aqueous electrolytes

The reduction of carbon dioxide emissions is crucial to reduce the atmospheric greenhouse effect, fighting climate change and global warming. Electrochemical CO2 reduction is one of the most promising carbon capture and utilization technologies, that can be powered by solar energy and used to make added-value chemicals and green fuels, providing grid-stability, energy security, and environmental benefits. A two-dimensional finite-elements model for porous electrodes was developed and validated against experimental data, allowing the design and performance improvement of a porous zinc cathode morphology and its operational conditions for an electrolyzer producing syngas via the co-electrolysis of CO2 and water. Porosity, pore length, fiber geometric shape, inlet pressure, system temperature, and catholyte flow rate were explored, and these parameters were thoroughly tuned by using the smart-search Nelder-Mead's multi-parameter optimization algorithm to achieve pronouncedly higher, industrial-relevant current density values than those previously reported, up to 263.6 mA/cm2 at an applied potential of −1.1 V vs. RHE.

Synergistic effect between Ni single atoms and Ni nanoparticles for effectively boosting sustainable co-electrolysis of CO2 and hydrazine

The intrinsic performance of single atom catalysts (SACs) to electrochemical CO2 reduction reaction (ECRR) is limited due to the absence of synergistic active sites. Herein, Ni single atom (NiSAs) and Ni nanoparticles (NiNPs) are co-loaded on nitrogen-doped hollow carbon spheres (N-HCSs) by a one-step calcination method, which exhibits high CO selectivity in H-type cell with aqueous solution or an ionic liquid as electrolyte. Particularly, NiSAs-NPs-N-HCSs demonstrate a CO selectivity of 98.98%, yielding an industrial level CO current density of 152.7 mA cm−2 in flow cell. In situ Raman spectroscopy and in situ infrared characterization technology confirm that *COOH and *CO are important intermediates in the ECRR process. Theoretical computations suggest that coexisting NiNPs can reduce the energy barrier of *COOH, thereby improving the ECRR performance, indicating the synergistic effect between NiSAs and NiNPs in the ECRR process. Moreover, NiSAs-NPs-N-HCSs is applied to the membrane electrode assembly system coupling the hydrazine oxidation reaction (HzOR), which can significantly reduce the voltage about 836 mV at 100 mA cm−2.

Effects of structural parameters of double-layer electrode on co-electrolysis in a solid oxide electrolysis cell

The advantages of double-layer electrode are available in the literature about single electrolysis of H2O and CO2 using solid oxide electrolysis cell (SOEC). However, for the co-electrolysis of CO2 and H2O, the influence of the structural parameters of the double-layer electrode on the co-electrolysis performance has been still unclear. In this study, a multi-scale model describing the co-electrolysis process of CO2 and H2O in SOEC is adopted. After model validation, a comparison of the performance of SOEC between a single-layer cathode and a double-layer cathode is conducted with different inlet flow rates. Moreover, parametric analyses are performed to investigate the effects of the thickness and porosity of cathode diffusion layer (CDL) and the internal composition of cathode function layer (CFL). The results show that when the CDL porosity increases from 0.45 to 0.65, the conversion ratio of H2 and CO increase by 10.17 % and 10.24 %, respectively. The optimal thickness of CDL (200 μm) for enhancing the durability of the cell and the preferable internal composition of CFL for improving the co-electrolysis performance are found within the scope of this study. This numerical analysis can provide guidance for the design of the double-layer cathode and the optimization of the co-electrolysis performance.

Preparation of Ni/YSZ Catalysts for Application of Solid Oxide Electrolysis Cell Methanation

Co-electrolysis of CO2 and steam using solid oxide electrolysis cells (SOECs) is a major focus of the CO2 conversion. Furthermore, SOECs have the potential to drive high value-added products with reduced carbon footprint. For example, the syngas (mixture of CO and H2) can be produced by SOEC-driven co-electrolysis of CO2 and steam, and utilized in the Fischer-Tropsch (FT) process for the synthesis of artificial hydrocarbon. The artificial hydrocarbons would be environmentally friendly fuels when CO2 is obtained from carbon capture and storage (CCS) technology. The Ni-based cermet, such as Ni with yttria-stabilized zirconia (Ni/YSZ), is a typical material of SOEC device, and Ni has been found to be an active catalyst for CH4 production (methanation). Therefore, use of the Ni/YSZ has potential to directly convert CO2 and H2O to CH4. In the catalytic process, the activity, selectivity and durability of the Ni/YSZ catalyst are significantly influenced by the structural property of Ni and YSZ, which is varied by the Ni loading and calcination conditions in addition to the studied reaction conditions. The preparation of Ni/YZS catalyst with high performance in co-electrolysis and methanation is still challenging.Herein, the preparation of the Ni/YSZ catalysts with enhanced activity in SOEC methanation was studied. The Ni/YSZ catalysts were prepared by wet impregnation, one of the catalyst preparation methods, and characterized by several conventional methods. Effects of Ni loading and calcination conditions on the performance of Ni/YSZ catalysts were examined by CO2 methanation. A Ni/YZS catalyst gave a high CO2 conversion of 86% and a high methane selectivity at around 300 ºC under ambient pressure. With Ni/YSZ prepared using the optimized method, we are planning to prepare tubular cells and evaluate their activity in SOEC methanation.

Co-electrolysis of seawater and carbon dioxide inside a microfluidic reactor to synthesize speciality organics

We report co-electrolysis of seawater and carbon dioxide (CO2) gas in a solar cell-integrated membraneless microfluidic reactor for continuous synthesis of organic products. The microfluidic reactor was fabricated using polydimethylsiloxane substrate comprising of a central microchannel with a pair of inlets for injection of CO2 gas and seawater and an outlet for removal of organic products. A pair of copper electrodes were inserted into microchannel to ensure its direct interaction with incoming CO2 gas and seawater as they pass into the microchannel. The coupling of solar cell panels with electrodes generated a high-intensity electrical field across the electrodes at low voltage, which facilitated the co-electrolysis of CO2 and seawater. The paired electrolysis of CO2 gas and seawater produced a range of industrially important organics under influence of solar cell-mediated external electric field. The, as synthesized, organic compounds were collected downstream and identified using characterization techniques. Furthermore, the probable underlying electrochemical reaction mechanisms near the electrodes were proposed for synthesis of organic products. The inclusion of greenhouse CO2 gas as reactant, seawater as electrolyte, and solar energy as an inexpensive electric source for co-electrolysis initiation makes the microreactor a low-cost and sustainable alternative for CO2 sequestration and synthesis of organic compounds.

Co-Electrolysis of CO2 and H2O Using an Exsoluted Perovskite Layer

Solid oxide electrolysers (SOECs) are a key class of technology that offers an efficient solution to storing renewable energy. One of the key characteristics of this technology is its ability to reduce both H2O and CO2. Currently, commercial cells are adapted from those made for power generation (i.e. SOFCs) and are not suitable for generating gas of higher quality than syngas due to the limited behaviour of the cells. Electrochemical analyses and gas chromatography were used to examine the ability of SOEC cells to improve gas quality. With the addition of a functional layer to the cathode, we achieved a complementary effect between electrochemical mechanisms taking place at the cathode and catalytic mechanisms involving CO2 and CO methanation. In spite of the fact that the results could be significantly improved, this approach demonstrated the potential for CO2 and H2O co-electrolysis at intermediate temperatures.

Preparation of Ni/YSZ Catalysts for Application of Solid Oxide Electrolysis Cell Methanation

Combination of co-electrolysis of CO2 and steam using solid oxide electrolysis cells (SOECs) and methane production (methanation) offers an attractive process for CO2 conversion to hydrocarbon fuels. Ni-based (Ni/YSZ is a typical example) SOECs could be used as catalytic reactor for CH4 production because Ni has been found to be an active catalyst for methanation. Therefore, Ni/YSZ SOECs could be used as catalytic reactor for methanation. Based on this concept, in this study we have prepared a Ni/YSZ material that can be used in the catalytic reactor. The performance of the prepared Ni/YSZ was evaluated as a catalyst for CO2 methanation. Ni/YSZ catalysts with a Ni loading of 55wt% calcined at 800-1100 ºC gave a high CO2 conversion of up to 86% and a high methane selectivity of >99% at 250-350 ºC of reaction temperature under ambient pressure.

Production of synthetic gas by the co-electrolysis of H2O and CO2 in the molten carbonate electrolyzer

The reversible operation of a commercialized molten carbonate fuel cell as an electrolyzer is attractive to store the surplus of renewable energy and convert CO2 into valuable fuel, like syngas (H2 and CO). This work aims to assess this capability by developing a model for the co-electrolysis of CO2 and H2O in the molten carbonate electrolysis cell (MCEC). Furthermore, a 1 MW power-to-gas system is simulated and optimized to maximize the process efficiency via a profound sensitivity analysis and a pinch heat integration analysis. The study's results reveal that when CO2 electrolysis occurs, there is a risk of reaching the limiting current density at lower values, thus affecting the cell's performance. As for the simulation, the process yields an efficiency of 68.87% with an electrolyzer's power density of 0.082 W/cm2 per cell, producing 1.3 tons/day of methane gas ready for injection into the natural gas network.

Electrocatalytic Reduction of CO2 Coupled with Organic Conversion to Selectively Synthesize High-Value Chemicals.

The electrochemical process of coupling electrocatalytic CO2 reduction and organic conversion reaction can effectively reduce the reaction overpotential and obtain value-added chemicals. Moreover, because of the diversity of substrates and the designability of coupling forms, more and more attention has been paid to this field. This review systematically summarizes the research progress of coupling electrolysis in recent years, (1) co-electrolysis of CO2 and organics at the cathode to obtain specific products with high selectivity, (2) replacing traditional anodic oxygen evolution reaction (OER) with other valuable oxidation reactions to improve energy utilization efficiency and economic benefits of CO2 conversion, (3) in an electrolytic cell without membrane, the cathode and anode jointly transform CO2 and organics to redox products. We hope that the examples and insights on coupling electrolysis introduced in this review can inspire researchers to further explore and innovate in this direction.

Prolonged Stability of Pb-Catalyzed CO2 Electroreduction to Methyl Formate in Acidic Methanol

Electrochemical CO2 reduction from renewable energy is a promising route to mitigate greenhouse gas emissions from waste sources while generating value-added products. CO2 electroreduction in methanol is particularly interesting due to the increased CO2 solubility compared to water and the propensity to form methyl formate, a product absent in aqueous electrolysis. Four factors have been identified as critical to achieving prolonged high selectivity for methyl formate production on a Pb cathode in methanol: high pH near the electrode, low bulk pH, low water content, and regeneration of Pb2+ sites. Increasing concentration of the formic acid product was observed to induce a selectivity shift toward hydrogen, which was mitigated by the in situ conversion of the formic acid to methyl formate via an esterification reaction. Furthermore, co-electrolysis of CO2 with dilute molecular oxygen (4% O2) led to Pb catalyst repair through in situ surface oxidation. Using CO2 and dilute O2 along with single-pass catholyte flow to maintain a low formic acid concentration, sustained high selectivity for methyl formate was attained at ∼60% faradaic efficiency at −20 mA cm–2 for over 72 h.

Tuning the product selectivity of CO2/H2O co-electrolysis using CeO2-modified proton-conducting electrolysis cells

This work demonstrates surface engineering as an effective strategy to modulate the surface adsorption characteristics of reaction intermediates, hence promoting CO2/H2O co-electrolysis to produce CH4 using PCECs.

Light, Heat and Electricity Integrated Energy Conversion System: Photothermal-Assisted Co-Electrolysis of CO2 and Methanol.

Strategy that can design powerful photothermal-catalysts to achieve photothermal-effect assisted coupling-catalysis is much desired for the improvement of energy conversion efficiency and redox product value in CO2 electroreduction system. Herein, a kind of bifunctional viologen-containing covalent organic framework (Ni-2CBpy2+ -COF) has been prepared and successfully applied in photothermal-assisted co-electrolysis of CO2 and methanol. Specifically, the FECO (cathode) and FEHCOOH (anode) for Ni-2CBpy2+ -COF can reach up to ≈100 % at 1.9 V with ≈31.5 % saved overall electricity-consumption when the anodic oxygen evolution reaction (OER) is replaced by methanol oxidation. The superior performance could be attributed to the cyclic diquats in Ni-2CBpy2+ -COF that enhance the photothermal effect (ΔT=49.1 °C) to accelerate faster charge transfer between catalyst and immediate species as well as higher selectivity towards desired products as revealed by DFT calculations and characterizations.

Co-electrolysis of CO2 and formaldehyde to ethanol: An inspiring asymmetric C−C coupling pathway

Selectively producing a target ethanol product is highly desired but challenging, especially when using CO 2 as a feedstock only. In this issue of Chem Catalysis , Han and co-workers describe a co-electrocatalytic conversion of CO 2 and formaldehyde (FA) toward ethanol, which expands the scopes of C−C coupling routes for CO 2 utilization. Selectively producing a target ethanol product is highly desired but challenging, especially when using CO 2 as a feedstock only. In this issue of Chem Catalysis , Han and co-workers describe a co-electrocatalytic conversion of CO 2 and formaldehyde (FA) toward ethanol, which expands the scopes of C−C coupling routes for CO 2 utilization.