High-pressure CO2 Research Articles

Experimental and simulation investigation of jet characteristics during the accidental release of high-pressure CO2 with different diameter leakage orifice

Understanding the near-field characteristics of leakage is essential for safety distance calculations and risk assessment of emergency response to a pipeline leakage. This paper presents a small-scale experiment and computational fluid dynamics model designed to investigate the transient characteristics of near-field parameters. The study also analyzes the effects of leakage orifice diameter on the transient characteristics of the near-field. The results show that a pipeline leak starts with the formation of a compression wave, which causes the air at the front of the stream to be compressed, heated and pressurized. CO2 is then released at high pressure, creating a strong expansion wave that keeps the fluid pressure below local atmospheric levels. For full-hole and large-hole leaks, the temperature drop and rate show a negative linear correlation with the size of the leak hole. Conversely, for small hole leaks with the ratio of hole diameter to pipe diameter values below 0.2, the temperature drop shows an opposite trend. As the ratio of hole diameter to pipe diameter values increases, the maximum diameter of the barrel drum-shaped disk gradually increases, but the maximum expansion angle of the jet decreases. It is hoped that this work will contribute to the improvement of research models that assess the consequences of potential high-pressure pipeline rupture scenarios.

Enhancing polymeric bone scaffolds mechanical characteristics using supercritical CO2 foaming and reinforcing agents

BackgroundAs an alternative to conventional medicine, scaffolds have emerged to mimic and/or replace damaged tissue. 3D porous matrix scaffolds made of biodegradable and biocompatible polymers, including PLGA, have proven to be of particular interest for use as bone substitutes in Tissue Engineering. MethodsThe study used high-pressure CO2 foaming to produce PLGA-based foams. Previously, melt-extrusion was used to introduce reinforcement agents, Mg(OH)2, Hydroxyapatite (HAp) and Mg, to achieve foams with improved properties. Foam morphology was analysed using SEM, EDS, and 3D scanner techniques, and foam strength was measured using compression tests. A statistical analysis was carried out to study the effect of pressure and temperature on foams pore size and hardness. Significant findingsThe foams produced were rigid, non-sticky and time-stable, and showed high porosity. The pressure was found to be the only significant variable to tune both porosity and cell densities of scaffolds. Setting a pore size at 500 μm, compressive stresses of 1.85 MPa, 3.81 MPa were achieved for Mg(OH)2 and HAp, respectively. Those results were comparable to literature´s trabecular bovine bone compression resistance of 4.2 MPa. This finding indicated the possibility of getting, at the same time, convenient results for porosity and mechanical resistance for their use as bone replacement agents. Finally, a 20 % w/w ratio of reinforcing agent was found to produce the best pore size-stress ratio.

Digital light processing 3D printing of polymerizable ionic liquids towards carbon capture applications

This study presents new 3D printable materials based on ad-hoc synthesized photocurable imidazolium ionic liquids (ILs) with bis(trifluoromethanesulfonyl)imide (NTf2)− as counterion and two different alkyl chain's structures at the cation, with enhanced CO2 capture properties. The molecular structure of the synthesized ILs was confirmed through NMR technique and a polymerization study was carried out, by means of photorheological tests and FT-IR analyses, on formulations containing a crosslinking monomer (PEGDA). The study confirmed the good reactivity of the formulations that makes them suitable for digital light processing (DLP) 3D printing technique. Simple membranes were then tested through high pressure CO2 uptake analysis to estimate their capture efficiency, comparing the results with the standard room temperature ionic liquid (RTIL) counterpart, and evidencing an increase of CO2 absorption regardless the pressure applied. At last, complex gyroid-like structures incorporating the synthesized ILs were successfully 3D printed, showing the remarkable ability of these materials to be processed with 3D printing technology while maintaining the great CO2 capture performances of ionic liquids. This preliminary work paves the way for the implementation of “ad-hoc” designs to create filters or devices to enhance the CO2 capture.

Dialkyl Carbonate Synthesis Using Atmospheric Pressure of CO2.

Dialkyl carbonates (DRCs) are valuable compounds widely used in the industry. The synthesis of DRC from CO2 has attracted interest as an alternative to the current method, which uses phosgene. However, the reported approaches for DRC synthesis from CO2 requires high-pressure and high-concentration CO2, resulting in elevated costs associated with CO2 purification and manufacturing facilities. In this report, we present an environmentally friendly method for producing DRC from low-concentration and low-pressure CO2 via a dehydration condensation approach without the use of halogenated alkylating agents. This method involves the formation of monoalkyl carbonate [BASE-H][ROC(O)O] using a strong organic base and alcohols, tetraalkyl orthosilicates as dehydrating agents, and CeO2 as the catalyst. Using the method, 39 and 30% of diethyl carbonate yields were accomplished with only 100 and 15 vol % CO2 (CO2/N2 = 15:85) gas bubbling at atmospheric pressure, even under reaction conditions with no large excess of either CO2, alcohol, or dehydration agent.

Numerical simulation study of the effect of different factors on supercritical CO2 BLEVE

Abstract Global warming is harmful to the environment and CO2 is one of the major greenhouse gases. CCS-EOR technology can increase oil production and sequester CO2. During the storage and transportation of high-pressure CO2, BLEVE may occur. In this study, the dynamic pressure parameters in the supercritical CO2 BLEVE process were numerically simulated by using numerical simulation, and the effects of initial temperature and initial charge on the dynamic pressure parameters in the supercritical CO2 BLEVE process were mainly discussed. By thoroughly investigating the dynamic pressure of BLEVE of supercritical CO2, we can better understand and predict the conditions under which such accidents occur, and further improve the safety of industrial processes.

Recent progress on the research of steel corrosion behavior and corrosion control in the context of CO2 geological utilization and storage: a review

Abstract CO2 geological utilization and storage (CGUS) is a key technology to achieve carbon neutrality goals. To apply CGUS on a larger scale, the issue of steel corrosion during the process must be addressed to mitigate technological risks. This paper provides an overview of CO2-induced steel corrosion mechanisms and identifies factors that influence corrosion. The impact of CO2 partial pressure, temperature, salinity, pH, impurities, and fluid flow on steel corrosion behavior are also discussed. With the presence of water, the corrosive effect of supercritical CO2 on steel is stronger than that of dissolved CO2 or gaseous CO2. As the temperature increases, the corrosion rate of steel first increases and then decreases. Increasing salinity and decreasing pH lead to an accelerated corrosion rate of steel. Corrosion inhibitors, coatings, and corrosion-resistant alloys are recommended protective measures against CO2-induced corrosion. Compared with coatings, corrosion inhibitors and corrosion-resistant alloys are more commonly used in CGUS projects. Future research directions include further exploration of the mechanisms underlying CO2-induced steel corrosion, clarifying the coupled effects of various environmental factors, and developing corrosion protection technologies under high-pressure and high-concentration CO2 conditions.

Carbon Neutral Design of Waste Energy Recovery System for LNG Power Plant Using Organic Rankine Cycle

In liquefied natural gas (LNG) power plants, a significant amount of heat and cold energy is consumed to capture and store carbon dioxide (CO2) emitted during the combustion of fossil fuels. The proposed system addresses this problem by utilizing the temperature difference between waste heat and cold energy as a power source to generate electricity. In this study, a novel waste heat and cold energy recovery system for a postcombustion LNG power plant was developed using an organic Rankine cycle (ORC). To design the proposed system, a process model was developed with the following five parts: (i) LNG vaporization, (ii) natural gas combined cycle (NGCC), (iii) amine scrubbing, (iv) CO2 liquefaction, and (v) CO2 injection. In the proposed system, waste LNG cold energy is used for lean amine cooling and CO2 liquefaction. The liquefied CO2 was pressurized to meet the injection pressure requirements. The ORC uses high-temperature exhaust gas from the NGCC as the heat source and high-pressure liquefied CO2 as the heat sink. The economic feasibility of the proposed system was demonstrated by an economic assessment, with the net profit evaluated by a sensitivity analysis considering variations in water, electricity, and equipment costs. Consequently, the proposed system exhibited an 18.6% increase in net power production compared to the conventional system. In addition, the net profit of the proposed system exhibited a 76.7% increase compared to the conventional system, confirming its economic feasibility.

Improvement of augmented free-water flash algorithm based on HV mixing rule and simulated annealing optimization algorithm

The calculation of three-phase equilibrium in CO2-hydrocarbon-water mixtures holds significant importance within numerical simulations, particularly in applications such as CO2-enhanced oil recovery and carbon dioxide sequestration. However, due to the non-ideality of CO2 and the polarity of water, three-phase equilibrium calculations often encounter convergence challenges. The augmented free-water flash algorithm [6], specifically focusing on CO2 dissolution in the aqueous phase, addresses the convergence challenges encountered by traditional three-phase flash algorithms. Despite its accuracy diminishes under conditions of high pressure and high CO2 concentrations, limiting its capability to accurately describe CO2 dissolution in oil-gas-water multiphase systems. The GE (excess Gibbs free energy) type mixing rule can be effectively integrated with equations of state, including PR and SRK, by utilizing activity models like NRTL and UNIFAC, which can be applied to the calculation of thermodynamic parameters for both nonpolar and polar systems and high-pressure complex systems. In this study, based on the augmented free-water assumption, we have developed a new augmented free-water three-phase flash algorithm for CO2/hydrocarbon/water mixtures. This algorithm integrates the PR equation of state with the NRTL activity model, employing the HV mixing rule for CO2-water interactions and the Van der Waals rule for other non-polar components. Furthermore, to enhance computational efficiency, the algorithm incorporates the simulated annealing global optimization algorithm, replacing Newton iteration to more effectively identify the global minima of the complex objective function. The example calculations show that the improved augmented free-water flash algorithm has higher accuracy and efficiency than the traditional augmented free-water flash algorithm. The augmented free-water three-phase flash algorithm proposed in this paper offers a precise model for phase equilibrium calculations essential for numerical simulations in CO2-enhanced oil recovery and carbon dioxide sequestration.

Influence of water saturation and water memory on CO2 hydrate formation/dissociation in porous media under flowing condition

Injection of high-pressure CO2 into depleted gas reservoirs can lead to low temperatures promoting formation of hydrate in the near wellbore area resulting in reduced injection rates. The design of effective mitigation methods requires an understanding of the impact of crucial parameters on the formation and dissociation of CO2 hydrate within the porous medium under flowing conditions. This study investigates the influence of water saturation (ranging from 20 % to 40 %) on the saturation and kinetics of CO2 hydrate during continuous CO2 injection. The experiments were conducted under a medical X-ray computed tomography (CT) to monitor the dynamics of hydrate growth inside the core and to calculate the hydrate saturation profile. The experimental data reveal increase in CO2 hydrate saturation with increasing water saturation levels. The extent of permeability reduction is strongly dependent on the initial water saturation: beyond a certain water saturation the core is fully blocked. For water saturations representative of the depleted gas fields, although the amount of generated hydrate is not sufficient to fully block the CO2 flow path, a significant reduction in permeability (approximately 80 %) is measured. It is also observed that the volume of water + hydrate phases increases during hydrate formation, indicating a lower-than-water density for CO2 hydrate. Having a history of hydrate at the same water saturation leads to an increase in CO2 consumption compared to the primary formation of hydrate, confirming the existence of the water memory effect in porous media.

Experimental study of leakage characteristics and risk prediction of N2-containing dense-phase CO2 pipelines in real transportation conditions

In the background of pipelines being widely used as a critical transportation chain for the carbon capture, utilization and storage (CCUS) process, studying the leak diffusion characteristics and risks of high-pressure impure CO2 pipelines in real transportation conditions is critical for process safety. Due to the limitations of the capture process and economic cost, the CO2 used for sequestration contains impurities in the range of 3% molar ratio, mainly N2. In this paper, the first leakage experiments involving dense-phase CO2 with a 3% molar ratio of N2 impurity were conducted on a large CO2 pipeline (258 m long and 233 mm inner diameter) using initial leakage orifices of 50 mm and 100 mm. Data concerning the thermodynamic properties of the impurity-containing leakage source were gathered for the analysis of phase transitions and flow alterations within the pipeline, as well as near-field temperature and the progression of the far-field concentration. The pressure-temperature curve in the pipe shifted along the dew line and then slowly shifted to the saturation line of pure CO2 with the influence of N2 impurities during the multiphase leakage phase. In the near-field region, cryogenic diffusion was governed by the boundary of the jet, with the control distance decreasing as the leakage orifice increased. In addition, an accurate prediction model of CO2 concentration on the leak axis was established based on the virtual source theory and the concentration decay law, and the predicted locations of CO2 concentrations at the 5% were 169 m and 210 m. As the leak orifice increases, the risk of low temperatures and high concentrations escalates, albeit with a sharp decrease in duration. These data provide accurate leakage characteristics and risk assessment for safely operating high-pressure CO2 processes under real conditions with impurities.

Localized corrosion in selective laser melted SS316L in CO2 and H2S brines at elevated temperatures

In this work, the passivation and localized corrosion of selective laser melted (SLM) stainless steel 316 L when exposed to high pressures of CO2 with the presence of H2S and Cl− at 25 °C and 125 °C were studied. Depletion of Cr/Mo was observed at the cell interiors and melt-pool boundaries (MPBs) compared to the cell boundaries. Volta potential differences obtained from scanning Kelvin probe force microscopy (SKPFM) showed that the MPBs were 8–20 mV lower than the matrix, while the cell interiors were 20–50 mV lower than the cell boundaries. Electrochemical impedance spectroscopy (EIS) and Mott–Schottky tests indicated a more defective passive film at 125 °C, and X-ray photoelectron spectroscopy (XPS) confirmed the formation of a less protective film with an increased S/O ratio at 125 °C than 25 °C. Initiation of localized corrosion was observed at the MPBs and pits formed after a week of immersion were wider by an order of magnitude at 125 °C than 25 °C, with evidence of cell-interior dissolution. While passivity was observed even at elevated temperatures, local chemical heterogeneities compromised the stability of the film and contributed to localized corrosion in SLM SS316L.

Threshold capillary pressure of caprocks for CO2 storage: Numerical insight on the dynamic and residual method

The dynamic threshold pressure method and the residual capillary pressure method provide an estimate of the threshold capillary pressure for CO2 storage. In the dynamic method, the threshold capillary pressure is determined by comparing the discharge measured when the CO2 starts flowing into the sample with the one measured when only water is flowing. In the residual method, a high CO2 pressure is applied on the vessel at the inlet of a water-saturated sample while water cannot flow from the vessel at its end. The threshold capillary pressure is estimated as the difference between the CO2 and the water pressures at the sample boundaries at equilibrium conditions.Sensitive analyses showed the impact of material properties and experimental conditions on results. Both methods allow estimating the threshold capillary pressure within a few days and the estimates are influenced by the applied pressures. The dynamic method estimate is not precautionary, and it tends to the exact value as the applied CO2 overpressure decreases. The residual method estimate is influenced by the drainage conditions and the volume of the vessels: it is generally precautionary and tends to increase with the volume of the vessels and the applied pressure. Suggestions for test interpretation and planning are also provided.

Direct carbonation of porous materials produced from self-hardened paper mill fly ash

A high-Ca fly ash generated from a paper mill using a fluidized bed boiler was used as the potential medium to sequester CO2 via the direct carbonation process. In this study, the fly ash samples were exposed to accelerated carbonation to produce hardened pastes. The influence of the porosity controlled by the amount of foam in the matrix for maximizing CO2 sequestration was determined. The effect of porosity on carbonation was evident. The samples prepared with 40 % foam and a water-to-fly ash ratio of 0.79 recorded porosities of 56.1 % (carbonated) and 66.8 % (naturally carbonated (NC)) with the lowest mechanical strength of 2.1 and 1.1 MPa, respectively. These naturally carbonated (NC) samples have been cured naturally without using high CO2 pressure. Meanwhile, the samples prepared with 10 % foam and a water-to-fly ash ratio of 0.5 recorded porosities of 41.1 % (carbonated) and 52.9 % (NC) with the highest strength at 10.2 and 4.6 MPa, respectively. The highest carbonation efficiency determined by thermogravimetric analysis was obtained from the carbonated samples with 40 % foam. Scanning electron microscopy–energy-dispersive spectroscopy depicted the areas with high Al/Si content but low Ca–O content (dark areas) and carbonated areas with high Ca–O content (bright areas). Mercury intrusion porosimetry was used to determine the pore size distribution, whereby the samples were dominated by large capillary pores, resulting in their high porosity in this study.

Inhibition effect of inert gas jet on gas and hybrid explosions caused by thermal runaway of lithium-ion battery

When lithium-ion batteries undergo thermal runaway in a confined space, the released gases and/or vapors or dust particles can lead to an explosion. An 8L cylindrical experimental vessel was constructed to study the inert effect of inert gases on battery-vented gas (BVG) in a confined vessel. Firstly, the inhibition effect and inert mechanism of CO2 and N2 on BVG explosion were analyzed by experiments and simulation software. The results show that the inert effect of CO2 on the BVG is significantly better than that of N2. This is because CO2 is not only better than N2 in physical explosion inhibition, but also participates in the chemical reaction. Secondly, the effect of the release of high-pressure CO2 gas on the explosion of the BVG in a closed container was simulated, showing that when the BVG is near the lower explosive limit, the CO2 jet will significantly increase the rate of explosion pressure rise of the BVG. This suggests that the inhibition effect of the CO2 jet is not as good as in premixed conditions. Finally, it is found that the inhibition effect of CO2 on the hybrid explosion is better than that of CO2 jet on the BVG. Since CO2 makes oxygen insufficient, leading to a reduction in the amount of graphite dust burned. The graphite dust and CO2 have a synergistic inhibition effect on the hybrid explosion. The above findings can provide a reference for the lithium-ion battery explosion inhibition method in the process industry.

Entropy Drives Accelerated Ion Diffusion upon Carbon Dioxide Expansion of Electrolytes.

Carbon dioxide-expanded liquids, organic solvents with high concentrations of soluble carbon dioxide (CO2) at mild pressures, have gained attention as green catalytic media due to their improved properties over traditional solvents. More recently, carbon dioxide-expanded electrolytes (CXEs) have demonstrated improved reaction rates in the electrochemical reduction of CO2, by increasing the rate of delivery of CO2 to the electrode while maintaining facile charge transport. However, recent studies indicate that the limiting behavior of CXEs at higher CO2 pressures is a decline in solution conductivity due to reduced polarity, leading to poorer charge screening and greater ion pairing. In this article, we employ molecular dynamics simulations to investigate the energetic driving forces behind the diffusive properties of an acetonitrile and tetrapropylammonium hexafluorophosphate (TPrAPF6) CXE with increasing CO2 concentration. Our results indicate that entropy drives solvent and electrolyte diffusion with increasing CO2 pressure. The activation energy of ion diffusion increases with higher concentrations of CO2, indicating that increasing the temperature may improve solution conductivity in these systems. This trend in the activation energies is traced to stronger cation-anion Coulombic interactions due to weaker solvent screening at high CO2 concentrations, suggesting that the choice of ion may provide a route to diminish this effect.

Structure-sensitive reactivities of O/Cu(1 0 0) studied by in situ NAP-STM

As the reactivities of materials originate essentially from the microstructures presenting on surface, the microscopic insight of structure-sensitive reactivity is crucial to understanding the nature of catalytic reactions. Herein, we have shown that both the structural evolution and the reactivity towards CO of O/Cu(100) exhibit remarkable structural sensitivity. Oxygen adsorbed on Cu(100) readily dissociate to oxygen dimers with gradually transforming to disordered c(2 × 2) structure (DCS). The DCS is further crystallized to missing-row reconstruction (MRR) structure preferentially at step edges prior to the presence of MRR and single-atom-high islands (SAHIs) on terraces. The DCS surrounding SAHI exhibits the highest reactivity towards CO through the enhanced CO adsorption and suitable geometric matching. At higher CO pressure, DCS and MRR react preferentially from step edges, followed by the DCS on terraces. Comparatively, isolated MRR shows unusual inertness due to the lack of microstructure that can trigger an initial reduction.

A novel organic-inorganic two-dimensional filler for composite coating with excellent mechanical and high-pressure CO2 anti-corrosion performance

organic-inorganic composite fillers were successfully prepared by a simple one-pot film-like coating of poly (α-cyanoethyl acrylate) (PECA) on mica. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TG) were used to analyze the structure, morphology, and chemical composition of the organic-inorganic composite filler and pure mica in detail. The organic-inorganic composite filler was added to epoxy resin to prepare a composite coating with long-lasting anti-corrosion and wear-resistance properties. The composite coating was characterized by electrochemical impedance spectroscopy (EIS), high-pressure CO2 corrosion tests, friction performance tests, differential scanning calorimetry (DSC), and adhesion performance tests. The mechanical test results showed that the average wear quality of the EP/P30&M(8/2) composite coating prepared with the modified filler was reduced to 65.7 % of that of the EP/MICA(8/2) coating. The addition of the modified filler to the coating substantially improved the wear resistance and crosslinking of the composite coating, reduced the porosity, increased the density, and effectively improved the overall performance of the composite coating. The results of high-pressure CO2 corrosion tests in harsh environments and electrochemical impedance spectroscopy showed that the composite coating had excellent barrier capacity. After high-pressure CO2 corrosion tests, the EP/P20&M(9/1) composite coating still has a high impedance modulus value of 6.348 × 1010 Ω/cm2 at 0.01 Hz, which is 5 orders of magnitude higher than that of the pure epoxy coating, and showsed excellent long-lasting corrosion resistance in EIS tests. This study provides new ideas for the industrial application of mica and the preparation of long-lasting anti-corrosion coatings.

Measurement and prediction of CO2 solubility in organic electrolytes for high pressure CO2 reduction

The electrochemical CO2 reduction reaction (CO2RR) to organic products is becoming increasingly important. Here, organic electrolytes play a crucial role, since adding salt to organic solvent allows an increase in the current density, and together with supercritical CO2 organic electrolytes suppress hydrogen evolution during the CO2RR. Since the selectivity to organic products depends on the CO2 content, CO2 solubility was investigated in organic electrolytes at different salt concentrations, pressures (up to 150 bar), and temperatures (25 °C and 70 °C). These organic electrolytes included the mixtures NaI-methanol, KSCN-methanol, (C2H5)4NBF4-acetonitrile, and (C4H9)4NBF4-acetonitrile. Afterwards, electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was applied to predict the CO2 solubility in these organic electrolytes. The results showed that i) CO2 solubility decreased with increasing temperature and salt concentration, ii) dissolving CO2 may cause a precipitation of salts, and that iii) ePC-SAFT allowed to qualitatively model the CO2 solubility in organic electrolytes

Effect of I- ligand and surface oxygen-containing groups on catalytic activity and stability of activated carbon-supported Pd catalysts in acetylene dicarbonylation

The support and ligand play a crucial role in regulating the catalytic performance, selectivity, and stability of heterogeneous catalysis. Herein, activated carbon (AC) supported palladium (Pd) catalysts (2.0 wt%) were prepared by impregnation for acetylene dicarbonylation. The oxygen-containing groups on the surface of the AC support were modulated by nitric acid (HNO3) to investigate metal–support interactions on the catalytic performance and stability of the Pd/AC. The characterization of the chemical composition and structure of the supports and catalysts demonstrates that high concentrations of oxygen-containing groups on the surface of the carbon support lead to the fine dispersion of Pd nanoparticles. Notably, the finely dispersed Pd/AC70 catalyst exhibited good activity and stability for acetylene dicarbonylation under high-pressure CO conditions after several rounds of regeneration. Furthermore, operational parameters including the type of support, co-catalyst (KI), and reaction time and temperature were identified for their impact on the reaction. It was found that I- anions serve as a co-catalyst and can ligate with Pd species, thereby preventing the leaching of Pd and improving reaction selectivity. This study presents a straightforward and sustainable modulation strategy to improve the dispersion of active metals, as well as to prevent the leaching and sintering of these metals during high-pressure CO reactions.

Promoting Selective CO2 Electroreduction to Formic Acid in Acidic Medium with Low Potassium Concentrations under High CO2 Pressure

AbstractElectrocatalytic CO2 reduction reaction (CO2RR) offers a sustainable pathway for the production of chemicals and fuels. Acidic electrolysis has been shown to be a promising strategy in order to avoid CO2 loss via the formation (bi)carbonate during reaction. Previous studies have been carried out in ambient CO2 pressure systems and have stressed the importance of adding high concentration of alkali cation (K+) in the catholyte to inhibit the hydrogen evolution reaction (HER) and achieve higher selectivity of CO2RR. Herein, CO2 reduction to HCOOH was performed in strong acid (pH 1) using a dendritic bismuth catalyst in a home‐designed high‐pressure electrochemical cell. At a CO2 pressure of 30 bar, we could achieve a high Faradaic efficiency of 100 % at 100 mA cm−2 at a KCl concentration of 3.0 M. With this first system that combines high pressure of CO2 and highly acidic catholyte, we show that pressurization offers an appropriate strategy to limit both HER and K+ dependence. Indeed we obtained a Faradaic efficiency of 34 % in the absence of K+ cations and 75–80 % in the presence of 1.0 M KCl under an applied current density of 100 mA cm−2.