Low-temperature CO Research Articles

Bridging fundamental science and applied science to accelerate CO2 electrolyzer scale-up

CO2 electrolysis coupled with renewable energy is an attractive option to decarbonize the chemical manufacturing sector. To accelerate the deployment of a commercially viable electrolyzer, there remains a need to de-risk scaling electrolyzers from the laboratory scale to industrially relevant conditions. An opportunity exists for the low-temperature CO2 electrolysis community can translate novel cell configurations and practices from adjacent fields to bridge the gap between fundamental sciences, and scaling a CO2 electrolyzer in geometric size, performance, and durability. Employing closed research loops that incorporate system-level analysis, continuum and atomistic modeling, and advanced characterization techniques can accelerate the rapid deployment of a CO2 electrolyzer.

Process analysis and comparative assessment of advanced thermochemical pathways for e-kerosene production

Climate change and energy supply are major driving forces for the promotion of sustainable fuels production. In the aviation sector, due to inherent difficulties to adopt electrification methods for long distance flights, the successful implementation of sustainable aviation fuel (SAF) is crucial for the achievement of greenhouse gas emissions mitigation strategies. This study presents four different pathways for the valorization of captured CO2 into synthetic kerosene using hydrogen and demonstrates the comparative assessment in terms of various technical and aspects such as hydrogen consumption, thermal energetic efficiency and produced e-kerosene quality. Two pathways are based on Fischer-Tropsch synthesis, a low-temperature CO conversion though reverse water-gas shift reaction and a high-temperature direct CO2 conversion, while the other two are based on the valorization and upgrading of light alcohols (methanol and ethanol) derived from CO2 hydrogenation. The process models were developed in Aspen Plus. Simulation results revealed that the low-temperature CO conversion pathway is the most efficient to maximize jet fuel yield with the lower energy and exergy losses. Indicatively for that case, 90.7% of the initial carbon is utilized for kerosene fraction synthesis, the overall thermal efficiency is 70.9% whereas the plant exergetic efficiency is 72.6%. The basic properties of the produced e-kerosene for all pathways meet with the required Jet-A1 specifications or are close to them.

Carbon monoxide+ammonia coupling denitration at low temperatures over manganese–cerium/activated carbon catalysts

To identify the mechanism of the low-temperature CO + NH3 coupling selective catalytic reduction (SCR) denitration process, a series of Mn–Ce/activated carbon catalysts differing in the Ce content were prepared and characterized via SEM, EDS, XRD, XPS, FTIR and evaluated in the CO + NH3 coupling SCR denitration. The results show that the denitrification rates of Mn-Ce/AC catalysts are in the order of 7Mn-3Ce/AC > 7Mn-5Ce/AC > 7Mn-1Ce/AC at a temperature range of 150 °C–300 °C and an oxygen content of 9%. A moderate Ce content provides a smooth catalyst surface with a homogeneous distribution of metal particles and pores, resulting in the optimization of the physical and chemical performance of the Mn-based catalyst. As a result, more active oxygen species and lattice defects are formed, which promoted the dispersion of active components on the catalyst surface, increased the adsorption sites of CO and NH3, and provided more active sites for denitration reaction. Mn4+ and Ce3+ both increased to varying degrees, and oxygen-containing functional groups carboxyl and lactone groups increased, which promoted the synergistic reaction between MnCe, enhancing the NO adsorption and conversion rate. At 150 °C–250 °C, the CO + NH3 coupling denitration is mainly governed by physical adsorption, whereas chemical adsorption is the predominant mechanism at 250 °C–300 °C. The denitration process includes four stages: reaction gas adsorption, adsorption molecular dissociation, catalytic denitration of metal active components and product desorption.

In Situ FTIR Spectroscopy for Scanning Accessible Active Sites in Defect-Engineered UiO-66.

Three UiO-66 samples were prepared by solvothermal synthesis using the defect engineering approach with benzoic acid as a modulator. They were characterized by different techniques and their acidic properties were assessed by FTIR spectroscopy of adsorbed CO and CD3CN. All samples evacuated at room temperature contained bridging μ3-OH groups that interacted with both probe molecules. Evacuation at 250 °C leads to the dehydroxylation and disappearance of the μ3-OH groups. Modulator-free synthesis resulted in a material with open Zr sites. They were detected by low-temperature CO adsorption on a sample evacuated at 200 °C and by CD3CN even on a sample evacuated at RT. However, these sites were lacking in the two samples obtained with a modulator. IR and Raman spectra revealed that in these cases, the Zr4+ defect sites were saturated by benzoates, which prevented their interaction with probe molecules. Finally, the dehydroxylation of all samples produced another kind of bare Zr sites that did not interact with CO but formed complexes with acetonitrile, probably due to structural rearrangement. The results showed that FTIR spectroscopy is a powerful tool for investigating the presence and availability of acid sites in UiO-66, which is crucial for its application in adsorption and catalysis.

One-step synthesized Bi5O7I for extremely low-temperature CO2 electroreduction

This work provides a scalable, one-step ultrasound-assisted reduction route, which prepares needle-tip Bi 5 O 7 I in a large quantity at ambient condition. At -50℃, the Bi 5 O 7 I-based flow cells can operate with a formate selectivity >90% and a large partial current density.

Graphene nanoplatelets promoted CoO-based catalyst for low temperature CO2 methanation reaction

Methanation of CO2 is an important reaction for reducing CO2 emissions in a power-to-gas system. Compared to cobalt supported on gamma-Al2O3, cobalt supported on graphene nanoplatelets (GNPs) showed significantly better performance for CO2 methanation. Cobalt supported on GNPs was capable of 15% conversion of CO2 to CH4 at temperatures below 250°C, compared to 5% for cobalt supported on Al2O3. In situ thermogravimetric analysis (TGA) demonstrated that the Co/GNP catalyst was stable to 400°C. The maximum catalyst mass-specific CH4 yield was obtained at a Co loading of 5wt% on GNPs; however, high Co loading on GNPs deactivated the reactivity of the Co/GNP catalyst. Transmission electron microscopy (TEM) demonstrated that 5wt% Co/GNPs had the smallest and most dispersed cobalt nanoparticles. Excessive loading of cobalt tended to form isolated large Co nanoparticles. X-ray photoelectron spectroscopy (XPS) and Raman spectrometry revealed that more CoO phases were maintained on the surface of 5wt% Co/GNPs, indicating that the interaction between the Co and the GNPs had more of an impact on cobalt’s redox capacity than did particle size, which ultimately affected cobalt’s active phase during the CO2 reduction process. Furthermore, Raman spectrometry demonstrated that Co loading led to an increase in graphene defects. Higher Co loading on GNPs resulted in fewer interfaces between Co and GNPs due to the agglomeration of Co nanoparticles.

Enhanced Stability of Low-Temperature CO Oxidation over K2CO3 Coupled CuO–MnOx–CeO2 Catalyst in the Presence of CO2, SO2 and NO2

Enhanced Stability of Low-Temperature CO Oxidation over K2CO3 Coupled CuO–MnOx–CeO2 Catalyst in the Presence of CO2, SO2 and NO2

An Active Manganese Promoted Ni/Al2O3 Catalyst for Low Temperature CO2 Methanation

An Active Manganese Promoted Ni/Al2O3 Catalyst for Low Temperature CO2 Methanation

A catalyst for low-temperature CO2 activation

A catalyst for low-temperature CO2 activation

Low-oxidation-state Ru sites stabilized in carbon-doped RuO2 with low-temperature CO2 activation to yield methane

The generation of methane fuel using surplus renewable energy with CO2 as the carbon source enables both the decarbonization and substitution of fossil fuel feedstocks. However, high temperatures are usually required for the efficient activation of CO2. Here we present a solid catalyst synthesized using a mild, green hydrothermal synthesis that involves interstitial carbon doped into ruthenium oxide, which enables the stabilization of Ru cations in a low oxidation state and a ruthenium oxycarbonate phase to form. The catalyst shows an activity and selectivity for the conversion of CO2 into methane at lower temperatures than those of conventional catalysts, with an excellent long-term stability. Furthermore, this catalyst is able to operate under intermittent power supply conditions, which couples very well with electricity production systems based on renewable energies. The structure of the catalyst and the nature of the ruthenium species were acutely characterized by combining advanced imaging and spectroscopic tools at the macro and atomic scales, which highlighted the low-oxidation-state Ru sites (Run+, 0 < n < 4) as responsible for the high catalytic activity. This catalyst suggests alternative perspectives for materials design using interstitial dopants.

Silver-manganese mixed oxide with crednerite structure as a catalyst for low-temperature catalytic CO oxidation

The paper describes the conditions for the preparation of AgMnO2 particles with the crednerite structure without impurity crystallized phases. It was shown that catalytic properties of AgMnO2 in CO oxidation might be different in dependence on the nature of the alkali-containing precursor used. The highest catalytic activity was achieved when using a combination of K- and Na-containing precursors. It has been found that the low-temperature catalytic activity of AgMnO2 increases noticeably with a decrease in the relative silver amount. An in situ X-ray diffraction study revealed a partial release of silver from crednerite structure with the formation of Ag0 particles when AgMnO2 was heated in a CO+O2 mixture to 150–200 °C, whereas heating to 250 °C followed by cooling to room temperature led to the incorporation of silver back into crednerite structure. The low-temperature catalytic activity of AgMnO2 correlates with the amount of weakly bounded oxygen species on the surface.

Hydrogen-controlled structural reconstruction of palladium-bismuth oxide cluster to single atom alloy for low-temperature CO oxidation

Palladium (Pd) has been widely regarded as a high-performance catalyst for various oxidative reactions, however, the actual structure of active site remains controversial due to structural evolution under operation conditions. Herein, we prepared a series of bismuth (Bi)-doped silica-supported Pd catalysts and found a hydrogen-controlled structural reconstruction mechanism of palladium-bismuth oxide cluster to single atom alloy to efficiently catalyze low-temperature CO oxidation. The formation of PdxBiyOz clusters with unique Pd−O−Bi coordination structure could enhance the sinter-resistance ability of Pd species. This structural evolution of active site is clearly uncovered by in-situ XAFS results, in which metallic Bi−Pd shell gradually generates as the increase of reduction temperature without any metallic Bi−Bi bond. More importantly, PdBi1 single atom alloy exhibits a good CO oxidation activity with a CO2 production rate of 413 μmolCO2·gPd−1·s−1 at 100 °C and excellent catalytic stability. Density function calculation (DFT) results indicate that there are geometric and electronic effects between Bi and Pd atoms, which favor total linear-CO adsorption, activate CO and O2 molecules, and reduce the barrier for the formation of OO-CO intermediates in PdBi1 single atom alloy.

Carbonation in Low-Temperature CO2 Electrolyzers: Causes, Consequences, and Solutions

Electrochemical reduction of carbon dioxide (CO2) to useful products is an emerging power-to-X concept, which aims to produce chemicals and fuels with renewable electricity instead of fossil fuels. Depending on the catalyst, a range of chemicals can be produced from CO2 electrolysis at industrial-scale current densities, high Faraday efficiencies, and relatively low cell voltages. One of the main challenges for up-scaling the process is related to (bi)carbonate formation (carbonation), which is a consequence of performing the reaction in alkaline media to suppress the competing hydrogen evolution reaction. The parasitic reactions of CO2 with the alkaline electrolytes result in (bi)carbonate precipitation and flooding in gas diffusion electrodes, CO2 crossover to the anode, low carbon utilization efficiencies, electrolyte carbonation, pH-drift in time, and additional cost for CO2 and electrolyte recycling. We present a critical review of the causes, consequences, and possible solutions for the carbonation effect in CO2 electrolyzers. The mechanism of (bi)carbonate crossover in different cell configurations, its effect on the overall process design, and the economics of CO2 and electrolyte recovery are presented. The aim is to provide a better understanding of the (bi)carbonate problem and guide research directions to overcome the challenges related to low-temperature CO2 electrolysis in alkaline media.

In situ DRIFTS and TPD studies on surface properties affecting SO2-resistance of Pt/TiO2 catalyst in low-temperature CO oxidation

By pre-calcining two TiO2 (P25 and anatase) supports at various temperatures, Pt/TiO2 of different Pt valence states, surface hydroxyls (OH), and peroxide contents were prepared. Pt/Anatase 450 and Pt/P25 450, whose supports were pre-calcined at 450 °C, performed excellently in the CO oxidation catalytic activity test using flue gas without water and SO2. Their low T50 (165 and 175 °C, respectively) and high TOF at 125 °C (0.204 and 0.247 s−1, respectively) of CO oxidation are attributed to the low stability of the adsorbed CO on Pt sites. Furtherly, in the catalytic test using water and SO2-containing flue gas, the catalysts using anatase supports achieved higher performance than P25 supports, showing T50 of 182−186 °C and TOF of 0.202−0.207 s−1 at 165 °C. The in situ DRIFTS study and TPD analysis indicate that OH participates in the sulfate formation. The limited hydroxylation on the anatase surface provides a small amount of OH, thereby mitigating the stable sulfate accumulation. Less stable sulfate on anatase than P25 gives rise to the high activity of anatase-supported catalysts.

Organic Non-Nucleophilic Electrolyte Resists Carbonation during Selective CO2 Electroreduction

The spontaneous reaction of CO2 with water and hydroxide to form (bi)carbonates in alkaline aqueous electrolytes compromises the energy and carbon efficiency of CO2 electrolyzers. We hypothesized that electrolyte carbonation could be mitigated by operating the reaction in an aprotic solvent with low water content, while also employing an exogenous non-nucleophilic acid as the proton donor to prevent parasitic capture of CO2 by its conjugate base. However, it is unclear whether such an electrolyte design could simultaneously engender high CO2 reduction selectivity and low electrolyte carbonation. We herein report selective CO2 electroreduction with low carbonate formation on a polycrystalline Au catalyst using dimethyl sulfoxide as the solvent and acetic acid/acetate as the proton-donating medium. CO2 is reduced to CO with over 90% faradaic efficiency at potentials relative to the reversible hydrogen electrode that are comparable to those in neutral aqueous electrolytes. 1H and 13C NMR studies demonstrate that only millimolar concentrations of bicarbonates are reversibly formed, that the proton activity of the medium is largely unaffected by exposure to CO2, and that low carbonation is maintained upon addition of 1 M water. This work demonstrates that electrolyte carbonation can be attenuated and decoupled from efficient CO2 reduction in an aprotic solvent, offering new electrolyte design principles for low-temperature CO2 electroreduction systems.

DRIFTS-MS Investigation of Low-Temperature CO Oxidation on Cu-Doped Manganese Oxide Prepared Using Nitrate Aerosol Decomposition.

Cu-doped manganese oxide (Cu-Mn2O4) prepared using aerosol decomposition was used as a CO oxidation catalyst. Cu was successfully doped into Mn2O4 due to their nitrate precursors having closed thermal decomposition properties, which ensured the atomic ratio of Cu/(Cu + Mn) in Cu-Mn2O4 close to that in their nitrate precursors. The 0.5Cu-Mn2O4 catalyst of 0.48 Cu/(Cu + Mn) atomic ratio had the best CO oxidation performance, with T50 and T90 as low as 48 and 69 °C, respectively. The 0.5Cu-Mn2O4 catalyst also had (1) a hollow sphere morphology, where the sphere wall was composed of a large number of nanospheres (about 10 nm), (2) the largest specific surface area and defects on the interfacing of the nanospheres, and (3) the highest Mn3+, Cu+, and Oads ratios, which facilitated oxygen vacancy formation, CO adsorption, and CO oxidation, respectively, yielding a synergetic effect on CO oxidation. DRIFTS-MS analysis results showed that terminal-type oxygen (M=O) and bridge-type oxygen (M-O-M) on 0.5Cu-Mn2O4 were reactive at a low temperature, resulting in-good low-temperature CO oxidation performance. Water could adsorb on 0.5Cu-Mn2O4 and inhibited M=O and M-O-M reaction with CO. Water could not inhibit O2 decomposition to M=O and M-O-M. The 0.5Cu-Mn2O4 catalyst had excellent water resistance at 150 °C, at which the influence of water (up to 5%) on CO oxidation could be completely eliminated.

Synergistic Catalysis at the Ni/ZrO2–x Interface toward Low-Temperature CO2 Methanation

The CO2 methanation reaction, which achieves the carbon cycle and gains value-added chemicals, has attracted much attention, but the design and exploitation of highly active catalysts remain a big challenge. Herein, zirconium dioxide-supported Ni catalysts toward low-temperature CO2 methanation are obtained via structural topological transformation of NiZrAl-layered double hydroxide (LDH) precursors, which have the feature of an interfacial structure (Ni-O-Zr3+-Vö) between Ni nanoparticles and ZrO2-x support (0 < x < 1). The optimized catalyst (Ni/ZrO2-x-S2) exhibits exceptional CO2 conversion (∼72%) at a temperature as low as 230 °C with a ∼100% selectivity to CH4, without obvious catalyst deactivation within a 110 h reaction at a high gas hourly space velocity of 30,000 mL·g-1·h-1. Markedly, the space-time yield of CH4 reaches up to ∼0.17 ·gcat-1·h-1, which is superior to previously reported Ni catalysts evaluated under similar reaction conditions. Both in situ/operando investigations (diffuse reflectance infrared Fourier transform spectroscopy and X-ray absorption fine structure) and catalytic evaluations substantiate the interfacial synergistic catalysis at the Ni/ZrO2-x interface: the Zr3+-Vö facilitates the activation adsorption of CO2, while the H2 molecule experiences dissociation at the metallic Ni sites. This work demonstrates that the metal-support interface effect plays a key role in improving the catalytic behavior toward CO2 methanation, which can be extended to other high-performance heterogeneous catalysts toward structure-sensitive systems.

Characterization of belitic cement mortars elaborated from shell and glass powders, microstructure and mechanical properties

The purpose of this study is to use waste glass as a source of silicium oxide SiO2 and shells as a source of calcium carbonate CaCO3 to replace traditional raw materials for the production of belite-rich clinkers and to investigate the hydration characteristics of the resulting mortars. After grinding, the raw materials were mixed to synthesize the belite phase in a heat treatment from 500 °C to 1000 °C. The belitic clinkers were, mixed with shell powder (CaCO3) and gypsum. The cements were synthesized with different proportions of belitic clinker and the hydration of the mortars was performed by increasing the percentage of belitic clinkers. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR) are used to characterize the mineralogy of hydrated samples during different curing times of 28, 65 and 90 days. The mechanical strength of mortars was measured for 28, 65 and 90 days. The results obtained show that the strength of all the samples increases with the curing time. The mortar containing 56 % of C2S has the highest value of mechanical strength 30.05 Mpa after 90 days of curing compared to other mortars. We have attempted here to review the development of high-belite cements by simple heat treatment at relatively low temperature and low CO2 release.

Thermodynamic analysis of a waste heat utilization based efficient liquefaction and low-temperature adsorption carbon capture hybrid system

Cryogenic CO2 capture can obtain high-pressure and pure CO2, but existing methods are inefficient as they usually discharge the waste heat of refrigeration. Therefore, a new hybrid system is proposed to recycle the waste cooling, heat, and uncondensable CO2 of liquefaction CO2 capture into low-temperature adsorption CO2 capture. This enhances the overall energy efficiency and the CO2 recovery rate over existing cryogenic CO2 capture without external input. Moreover, it enables practical sub-zero temperature CO2 adsorption while lowering the desorption temperature to 70 °C. This system is analyzed by coupling the liquefaction CO2 capture and low-temperature adsorption CO2 capture thermodynamic models, whose heat and cooling needs are compared to that available by a vapor compression cycle. Results show that for 10% mol. CO2 flue gas, the proposed system is optimal at −53 °C and 5 MPa to yield a 2nd law efficiency of 9%, a CO2 recovery rate of 80%, and specific energy consumption of under 1.65 MJ/(kg of CO2). As the cooling demand is typically twice the heat needed for sorbent regeneration, a vapor compression cycle designed to meet the former can naturally meet the latter. Ultimately, the new hybrid system represents a new carbon capture technology with better potential to achieve carbon neutrality via waste heat utilization.

Corrosion Behaviors of N80 and 1Cr Tubing Steels in CO2 Containing Downhole Environment—A Case Study of Underground Gas Storage in LiaoHe Oil Field

In order to evaluate the effect of chromium content in carbon steel on the corrosion resistance of carbon steel materials, the corrosion behavior of 1Cr and N80 steels was investigated in this study by immersion weight loss method under three different CO2 partial pressure and temperature conditions in formation water for 72, 168 and 336 h. Detailed material surface morphological characterization was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and confocal laser scanning microscopy (CLSM). The results show that the pitting corrosion of N80 carbon steel is serious at medium temperature and low CO2 partial pressure (50 °C, 0.30 MPa), and the corrosion rate is significantly higher than that of 1Cr steel. However, at high-temperature and high CO2 partial pressure (100 °C/0.63 MPa and 114 °C/0.73 MPa), 1Cr steel is more inclined to the mesa corrosion dominated by local corrosion characteristics, and the corrosion rate is seriously higher than that of N80 steel with uniform corrosion. From the experimental results, we can know the corrosion resistance of carbon steel and 1Cr steel is not only affected by the corrosion environment, but also depends on the formation process of the product film, as well as its compactness and integrity characteristics. At low-temperature and low CO2 partial pressure, 1 wt.% chromium content can provide a certain degree of corrosion resistance, while high temperature and high partial pressure can broaden the application window of carbon steel N80 and weaken the corrosion inhibition effect of chromium.