A New Method of Low-Temperature Methanol Synthesis

Methane hydrate exists in huge amounts in certain locations, in sea sediments and the geological structures below them, at low temperature and high pressure. Production methods are in development to produce the methane to a floating platform. There it can be reformed to produce hydrogen and carbon dioxide, in an endothermic process. Some of the methane can be burned to provide heat energy to develop all needed power on the platform and to support the reforming process. After separation, the hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform can be separated from other gases and then sequestered in the sea as carbon dioxide hydrate. In this way, hydrogen is made available without the release of carbon dioxide to the atmosphere, and the hydrogen could be an enabling step toward a world hydrogen economy.

Machine learning assisted prediction of copper-based catalysts towards carbon dioxide electroreduction into carbon monoxide

A balance between greenhouse gases production and capture is required to tackle the global warming resulting from them. Carbon dioxide (CO2) is considered as a waste gas but it is also a potential feedstock. Indeed, with the utilization of renewable energies, carbon dioxide electroreduction reaction (CO2RR) can generate useful products within a carbon neutral strategy. Practical CO2 conversion requires catalysts capable of mediating the efficient formation of a single product at high current densities over a long time (1). Among the potential products, carbon monoxide (CO) requires only 2 electrons to be generated which facilitate to reach high faradaic efficiencies. CO is also an important precursor in the chemical industry and its market is large enough to receive this new production method. (2)High current densities have been hit with copper-based catalysts but these catalysts tend to be nonspecific to only one product. Solid-state catalysts struggle to maintain a relevant selectivity at low overpotentials. They also rely mostly on noble metals or use deposition methods that are not upscalable for an industrial use.Molecular catalysts can be tuned to be highly selective towards CO at low overpotential but cannot operate CO2RR at relevant current densities for commercial purposes. Best molecular catalysts are close to 100 % faradaic efficiency for CO but the strongest production rate reported is 33 mA/cm² (3). This current density is more than 5 times smaller than the industrial relevant scale. Moreover, these catalysts are usually fragile over time with reported electrolysis less than ten hours.In this presentation, we will show that Cobalt Phthalocyanine (CoPc) - a widely available and known molecular catalyst - is able to compete with solid-state catalysts. We will illustrate how the CO2 delivery to a gas diffusion electrode can increase the reactivity of a molecular catalyst. We succeed to operate CO2RR with 95% faradaic efficiency for CO at 150 mA/cm² and an overall cell potential of 2.45 V. (4) We will also emphasize how the tunability of such catalysts can lower the reaction overpotential and increase the stability. (5)1: Ind. Eng. Chem. Res. 2018, 57, 2165−21772: Acc. Chem. Res. 2018, 51, 4, 910-9183: ACS Energy Lett. 2018, 3, 10, 2527-25324: Science 2019, 365, 6451, 367–3695: Nature comm. 2019, 10, 3602

Kinetic study of steam reforming of methanol over copper-based catalysts

Hydrogen, an energy-intensive and clean power source, has been treated as an ideal energy carrier to replace the coal and oil based global energy system for the more sustainable economic development. Especially, with the increasing finical support from worldwide in the researching of renewable energy both for the public and military using. Generally, hydrogen cycling includes three steps: (1) the continuously large scale hydrogen generation; (2) the safe and efficient hydrogen storage and transportation; (3) the efficient conversion of hydrogen to electricity or other forms of energy. For the using of hydrogen, a representative example is polymer electrolyte membrane fuel cells (PEMFCs) which has been widely studied. However, the bottle-neck for the bursting of hydrogen economy besides the effective using of hydrogen lies in the efficient generation and safe storage of hydrogen. Recently, our research group developed α-molybdenum carbide (α-MoC) supported Au and Pt catalysts for the low temperature water-gas shift (WGS) reaction and aqueous-phase reforming of methanol, respectively, both were essential reactions for industrial hydrogen generation. The WGS reaction (where carbon monoxide plus water yields hydrogen and carbon dioxide) is an important process for hydrogen generation and carbon monoxide removal in various energy-related chemical operations. This equilibrium-limited reaction is favored at a low working temperature. However, the reported catalysts by now always show unsatisfied performance under low operating temperatures and no catalysts ever reported reaching the activity of 0.1 molCO molmetal−1 s−1 below 150°C. Meanwhile, potential application in fuel cells also requires a WGS catalyst to be highly active, stable, and energy-efficient to match the working temperature of on-site hydrogen generation and consumption units. Concerning this problem, we synthesized layered gold clusters on a molybdenum carbide (Au/α-MoC) substrate to create an interfacial catalyst system for the ultralow-temperature WGS reaction. Water was activated over α-MoC at 30°C, whereas carbon monoxide adsorbed on adjacent Au sites was apt to react with surface hydroxyl groups formed from water splitting, leading to a high WGS activity reaching 1.05 molCO molmetal−1 s−1 under 120°C which is one order of magnitude higher than the early reported catalysts. Beside the Au/α-MoC for robust WGS reaction, we also developed highly distributed single atom Pt supported by molybdenum carbide (Pt/α-MoC) for aqueous-phase reforming of methanol. With the reforming of methanol and water, hydrogen with a high gravimetric density of 18.8% by weight can be in situ released. The average turnover frequency of Pt/α-MoC can reach 18046 mol of hydrogen per mole of platinum per hour at 190°C, which is two order of magnitude higher than the traditional catalysts. Based on the X-ray absorption fine structure (XAFS) and single atom resolution electron microscopy characterization results, Pt was determined to be atomic dispersed over α-MoC support at the low metal loadings, which maximized the exposure of Pt atom. Based on reaction mechanism investigation and DFT calculation, Pt/α-MoC was proved to be a bifunctional catalyst, with α-MoC support dissociating the O−H bond of H2O and methanol at low temperature, atomic dispersion of Pt scissoring C−H bond of CH3OH. The effectively reforming of intermediates with surface hydroxyls generate CO2 at the interface of Pt/α-MoC. The excellent performance of our catalytic system provide a new strategy for the efficient low-temperature hydrogen production and storage. In this short perspective, we introduce the new findings by our group and also summarize the recently developed representative catalysts involving the low temperature water-gas shift reaction and aqueous-phase reforming of methanol. We hope it can provide a reference for the future designing of catalysts in the field of hydrogen production and storage.

The purpose of this work is to produce high purity hydrogen stream from methanol by an integration of steam reformer and preferential oxidation of CO unit. For methanol steam reformer (MSR), Catalytic activities of Ce-Mg promoted Cu/Al₂O₃ catalysts was investigated in terms of the methanol conversion level, carbon monoxide (CO) selectivity and hydrogen (H₂) yield. It was found that the Ce-Mg bi-promoter catalysts gave a higher performance due to magnesium penetration into the cerium structure causing oxygen vacancy defects on the ceria. A face-centered central composite design response surface model was then designed to optimize the condition at a 95% confidence interval revealed an optimal copper level of 46–50 wt%, Mg/(Ce+Mg) of 16.2–18.0%, temperature of 245–250 °C and S/C ratio of 1.74–1.80. In case of preferential oxidation of CO unit, catalytic activities of copper based catalysts over a series of modified ceria support was investigated in terms of the CO conversion level and carbon dioxide (CO₂) selectivity. The results revealed that the Ce-Mg support gave a higher performance due to magnesium promoted water-gas shift reaction and improved nanorods arrangement. Box-Behnken design response surface model was then designed to optimize the condition at a 95% confidence interval revealed an optimal CO level of 0.65-0.75%, O₂ level of 0.80-0.90% and temperature of 130–140 °C. When integrating both MSR and PROX unit, high purity hydrogen was yielded around 45-47% without CO detected at a rate of ~120 L d⁻¹ g.cat⁻¹.

Typically, in the heterogeneously catalyzed hydrogenation of carbon monoxide, copper-based catalysts are very selective for the synthesis of methanol, while cobalt-based catalysts exhibit Fischer-Tropsch activity with high selectivity to hydrocarbons. Mixed copper-cobalt catalysts have been reported to show, in various degrees [1–4], selectivity for higher alcohol formation. Of particular interest are the copper-cobalt catalysts developed by Sugier and co-workers [3,4] at the Institut Francais du Petrole (IFP). Most of these catalysts contain aluminum, chromium or zinc, and small amounts of alkali, so that their composition corresponds to that of alkalized conventional copper-based methanol synthesis catalysts modified by the addition of cobalt. With these catalysts, high yields of higher alcohols were obtained under methanol synthesis conditions, and, in contrast with other copper-cobalt systems [1–2], there was no appreciable methanation, and little [3] or moderate [4] formation of higher hydrocarbons.

Hydrogen generation by steam reforming of methanol over copper-based catalysts for fuel cell applications

A copper-based catalyst can be utilized to synthesize methanol from syngas containing carbon dioxide as well as water at low temperature and low pressure. However, the agglomeration of the metallic copper and zinc oxide decreased the catalyst surface area and the Cu-specific surface area. In order to prevent the sintering, the supercritical CO2 was used to extract water from the catalyst precursor. Our results demonstrate that the Cu-specific surface area was the essential factor to affect the catalytic activity. A larger Cu-specific surface area would cause higher methanol synthesis activity. The optimized supercritical CO2 drying condition was at 308 K and 8.0 MPa for 3 h when the methanol yield reached 44.8%.

Formation of carbon oxides during tobacco combustion: Pyrolysis studies in the presence of isotopic gases to elucidate reaction sequence

The water-gas shift (WGS) reaction (where carbon monoxide plus water yields dihydrogen and carbon dioxide) is an essential process for hydrogen generation and carbon monoxide removal in various energy-related chemical operations. This equilibrium-limited reaction is favored at a low working temperature. Potential application in fuel cells also requires a WGS catalyst to be highly active, stable, and energy-efficient and to match the working temperature of on-site hydrogen generation and consumption units. We synthesized layered gold (Au) clusters on a molybdenum carbide (α-MoC) substrate to create an interfacial catalyst system for the ultralow-temperature WGS reaction. Water was activated over α-MoC at 303 kelvin, whereas carbon monoxide adsorbed on adjacent Au sites was apt to react with surface hydroxyl groups formed from water splitting, leading to a high WGS activity at low temperatures.

The current climate crisis has directed much focus onto strategies for limiting carbon dioxide (CO2) emissions and preventing its accumulation in the atmosphere. In pursuit of carbon-neutrality, there has been huge interest in developing carbon-conversion processes such as CO2 electroreduction (CO2ER), which can convert CO2 into valuable single- or multi-carbon products, such as carbon monoxide (CO), formate (HCOOH), methane (CH4), ethylene (C2H4) and more. Specifically, copper-based catalysts have received significant attention for their unique ability to reduce CO2 to multi-carbon products but are however limited by poor selectivity, stability and energy efficiency.1 Recent studies have shown that electrochemical reactions such as CO2ER can be enhanced using plasmonic catalysts.2 Plasmonic excitation via localized surface plasmon resonance (LSPR) is achieved by directing light energy onto the surface of a plasmonic nanomaterial. This energy is then harvested by the catalyst, accelerating electron transfer and boosting performance. Gold and silver-based materials are the most extensively studied plasmonics, due to their excellent plasmonic properties. Lately, plasmonic copper-based materials as catalysts for CO2ER has been receiving attention.3 Plasmonic enhancement has the potential to address some of the key issues associated with copper surfaces, including as poor selectivity and efficiency. As such, this study investigates plasmon-enhanced CO2ER on synthesized ZnO-supported Cu (Cu/ZnO) catalysts.Cu/ZnO nanoparticles of varying Cu loadings (0, 10, 60, 80, 100%) were synthesized using a modified polyol method.4 The nanoparticles were characterized through X-ray diffraction (XRD), UV-vis spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). Electrochemical performance and stability with and without light-enhanced conditions were assessed using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) in a three-electrode quartz spectroelectrochemical cell illuminated by a high-power white halogen lamp. For product analysis and long-term stability tests, a sealed H-type photoelectrochemical cell was utilized. Gas chromatography (GC) and nuclear magnetic resonance (NMR) was used to detect and quantify CO2ER products. To gain some mechanistic understanding into reaction intermediates and pathways, in-situ polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) tests were conducted with and without light.Electrochemical tests for the Cu/ZnO catalysts were performed in CO2-saturated 0.1M KHCO3 electrolyte. LSV results display higher current densities under light conditions for catalysts with higher Cu loadings, namely 60Cu/ZnO, 80Cu/ZnO and Cu, suggesting that the plasmonic properties of Cu are responsible for the enhancement (Fig. 1a). Additionally, lower onset potentials were observed under light conditions and with increasing Cu content, with the Cu catalyst exhibiting the lowest onset potential under light conditions. Chopped-light photocurrent responses were recorded for the 60Cu/ZnO, 80Cu/ZnO and Cu catalysts at -0.75 V vs. RHE (Fig. 1b). The Cu catalyst exhibited a significant current density enhancement of nearly 35% under light conditions. In contrast, the enhancements observed for 60Cu/ZnO and 80Cu/ZnO were less pronounced, attributed to their lower Cu content, which correlates to lower CO2ER activity and plasmonic enhancement. References Birdja, Y. Y.; Pérez-Gallent, E.; Figueiredo, M. C.; Göttle, A. J.; Calle-Vallejo, F.; Koper, M. T. M. Advances and Challenges in Understanding the Electrocatalytic Conversion of Carbon Dioxide to Fuels. Nat Energy 2019, 4 (9), 732–745.Germano, L. D.; De Angelis, L. D.; Córdoba De Torresi, S. I. Plasmon-Enhanced Electrochemistry: A Sustainable Path for Molecular Sensing and Energy Production. Current Opinion in Electrochemistry 2024, 43, 101422.Morin Caamano, T.; Houache, M. S. E.; Couillard, M.; Turnbull, M.; Zhou, J.; Wang, J.; Weck, A.; Abu-Lebdeh, Y.; Baranova, E. A. Plasmon-Enhanced CO2 Electroreduction on Copper, Silver, and Copper-Silver Nano-Catalysts. Electrochimica Acta 2024, 488, 144182.Wang, J.; Sandoval, M. G.; Couillard, M.; González, E. A.; Jasen, P. V.; Juan, A.; Weck, A.; Baranova, E. A. Experimental and DFT Study of Electrochemical Promotion of Cu/ZnO Catalysts for the Reverse Water Gas Shift Reaction. ACS Sustainable Chem. Eng. 2024, 12 (29), 11044–11055. Figure 1 . Electrochemical testing of Cu/ZnO catalysts in CO2-saturated 0.1M KHCO3 electrolyte. (a) Linear-sweep voltammograms, under no light and with light, swept at 1 mV/s between -0.1 and -1.0 V vs. RHE, (b) chopped-light photocurrent responses of 60Cu/ZnO, 80Cu/ZnO and Cu catalysts at -0.75 V vs. RHE. Figure 1

Liquid fuel synthesis via CO2 hydrogenation by coupling homogeneous and heterogeneous catalysis

Boosting CO2 Conversion with Terminal Alkynes by Molecular Architecture of Graphene Oxide-Supported Ag Nanoparticles

Catalytic activation of CO 2: Use of secondary CO 2 for the production of synthesis gas and for methanol synthesis over copper-based zirconia-containing catalysts