Carbon Monoxide Impurities Research Articles

Pulse Oxidation to Mitigate Carbon Monoxide Poisoning in Electrochemical Hydrogen Pumps

Electrochemical hydrogen pumps (EHP) play a pivotal role in developing clean and sustainable energy systems, with applications ranging from hydrogen transportation to stationary power generation. However, the presence of carbon monoxide (CO) in the hydrogen stream can pose a significant challenge, leading to catalyst poisoning and decreased pump efficiency. This work introduces a novel and effective strategy to mitigate carbon monoxide poisoning in EHPs using pulse oxidation. Pulse oxidation involves periodically applying a positive increase in current to the electrode surface to create an anode overpotential that oxidizes CO from the catalyst surface. This technique offers a dynamic and precise means of selectively removing CO impurities from the hydrogen stream. Tailoring the current pulses to the specific electrochemical characteristics of CO can achieve targeted removal without compromising the overall pump performance. The study explores the influence of CO gas feed rate, pulse width, operating current, and pulse interval on EHP performance. Results show that optimizing these parameters significantly impacts separation efficiency, energy efficiency, and power consumption. This strategy promises to improve the reliability and longevity of EHPs in real-world applications. By effectively addressing carbon monoxide poisoning, pulse voltammetry opens new avenues for developing robust and efficient hydrogen pumping systems, contributing to the broader goal of establishing hydrogen as a clean energy carrier in a sustainable future.

Carbon monoxide impurities in hydrogen detected with resonant photoacoustic cell using a mid-IR laser source

We report on a photoacoustic sensor system based on a differential photoacoustic cell to detect the concentration of CO impurities in hydrogen. A DFB-QCL laser with a central wavelength of 4.61 µm was employed as an exciting source with an optical power of 21 mW. Different concentrations of CO gas mixed with pure hydrogen were injected into the photoacoustic cell to test the linear response of the photoacoustic signal to the CO concentration. The stability of the long-term operation was verified by Allan-Werle deviation analysis. The minimum detection limit (MDL, SNR=1) results 8 ppb at 1 s and reaches a sub-ppb level at 100 s of integration time. Dynamic response of the system is linear and has been tested up to the concentration of 6 ppm. Saturation conditions are expected to be reached for CO concentration larger than 100 ppm.

Experimental evaluation of the purity of medical oxygen obtained by adsorption technology with pressure fluctuations taking into account the variability of the parameters of the incoming air

This study presents the results of the evaluation of the purity of medical oxygen obtained by adsorption technology with pressure fluctuations, taking into account the variability of the parameters of the incoming air, and the results of the correlation analysis of data obtained from the monographs of the European and American Pharmacopoeias. The quality of oxygen obtained from air that meets sanitary standards and under conditions of the “worst case,” while fixing the time of the output of the slip signal of monoxide and carbon dioxide as marker gases, was assessed. The slip time under the experimental conditions was 13 h 22 min. The composition of the gas produced by installation was analyzed. Impurities of nitrogen, argon, and water were recognized as predominant quantitatively. Nitrous gases and sulfur dioxide were not detected. A comparative assessment of the data on medical oxygen (93%) presented in the European EP 8. 0 (No. 2455) and the American USP 38-NF (No. 4180) pharmacopeias showed that no single approach is available to assess the quality of 93% medical oxygen in pharmaceutical practice worldwide. The authors of the above-mentioned pharmacopeias note that installations for obtaining 93% medical oxygen, implementing adsorption technology with pressure fluctuations, must be equipped with gas-analytical devices to quantify the level of at least two impurities: carbon monoxide and dioxide. In general, the data obtained indicate that when obtaining 93% medical oxygen by adsorption technology with pressure fluctuations from air corresponding to sanitary and hygienic indicators (clean), the resulting gas did not contain impurities requiring quantitative assessment and/or identification. If oxygen in its pure form is rarely supplied to the patient, its further dilution to 40%–60% is more often required, and the content of hypothetically possible impurities becomes negligible. However, the technology of air separation on molecular sieves is a complex physicochemical (thermodynamic) process, and its effectiveness depends on the component composition of the incoming air, which may change when working under unfavorable environmental conditions in various locations. In this regard, medical oxygen production plants that implement this technology must employ gas-analytical devices to quantify the level of carbon dioxide and carbon monoxide impurities without fail.

Photoacoustic Heterodyne CO Sensor for Rapid Detection of CO Impurities in Hydrogen.

Hydrogen (H2) fuel cells have been developed as an environmentally benign, low-carbon, and efficient energy option in the current period of promoting low-carbon activities, which offer a compelling means to reduce carbon emissions. However, the presence of carbon monoxide (CO) impurities in H2 may potentially damage the fuel cell's anode. As a result, monitoring of the CO levels in fuel cells has become a significant area of research. In this paper, a novel photoacoustic sensor is developed based on photoacoustic heterodyne technology. The sensor combines a 4.61 μm mid-infrared quantum cascade laser with a low-noise differential photoacoustic cell. This combination enables fast, real-time online detection of CO impurity concentrations in H2. Notably, the sensor requires no wavelength locking to monitor CO online in real-time and produces a single effective signal with a period of only 15 ms. Furthermore, the sensor's performance was thoroughly evaluated in terms of detection sensitivity, linearity, and long-term stability. The minimum detection limit of 11 ppb was obtained at an optimal time constant of 1 s.

The influence of Pd4Cr6@(NH2)M-MOF(Cr) catalyst on components of formic acid dehydrogenation gaseous products

ABSTRACT In the dehydrogenation of formic acid, catalyst has a great influence on the composition and formation rate of gaseous products. However, the hydrogen used in fuel cells has strict requirements on the content of carbon monoxide impurities. Therefore, it is very important to study the relationship between catalyst components and their synergistic effects and the composition of gaseous products. The role of Pd-Cr bimetallic nanoparticles supported on amino modified Cr-based metal-organic framework catalyst (Pd4Cr6@(NH2)M-MOF(Cr)) in the formic acid dehydrogenation was explored through comparative experiments and catalyst characterization. Results show that both Cr-based metal-organic framework (MOF(Cr)) and amino-modified Cr-based metal-organic framework ((NH2)M-MOF(Cr)) have no effect on promoting the generation of gaseous products. The presence of Cr and NH2 groups in Pd4Cr6@(NH2)M-MOF(Cr) greatly improves the formation rate of H2 and CO2 products, the gas production rate of Pd4Cr6@(NH2)M-MOF(Cr) is 2.89 times that of Pd4@(NH2)M-MOF(Cr), and the gas production rate of Pd4Cr6@(NH2)M-MOF(Cr) is 6.26 times of Pd4Cr6@MOF(Cr). However, the formation rate of H2 increases more in the presence of Cr. Synergy of Pd-Cr and Pd-NH2 in the Pd4Cr6@(NH2)M-MOF(Cr) catalyst promotes CO formation.

Enhanced anti-poisoning performance against carbon monoxide of LaNi4.7Al0.3 alloy encapsulated in polymethyl methacrylate

LaNi4.7Al0.3 alloy has been applied in hydrogen recovery system due to the favorable absorption and desorption property. Herein, the LaNi4.7Al0.3 alloy is encapsulated in polymethyl methacrylate (PMMA) by a simple physical mixing method, and the hydrogen absorption and desorption properties in the hydrogen containing 300 ppm carbon monoxide (CO) are investigated. PMMA can accommodate the powdered alloy particles and prevent the contact of CO and alloy. The hydrogen absorption and desorption kinetics properties in hydrogen gas with 300 ppm CO impurities of the LaNi4.7Al0.3 alloy encapsulated in PMMA matrix are improved. PMMA can be used as a potential material to enhance the anti-poisoning property of hydrogen storage alloys.

Impact of anode catalyst loadings and carbon supports to CO contamination in PEM fuel cells

Hydrogen fuel quality is important for the successful commercialization of PEM (proton exchange membrane) fuel cell vehicles (FCVs) because impurities can adversely affect the normal operation of FCVs both immediately and during their lifetime operation. Among the impurities specified in H2 quality standards, CO (carbon monoxide) is known to have one of the greatest impacts on fuel cells because of the immediate decrease in performance at low concentrations. CO impurity levels of only 0.2 ppm, as specified in the H2 quality standards, were found in H2 refueling stations with adverse impacts to PEM fuel cell operation. In this study CO impurity testing was conducted on single cells based on an extensive design of experiments (DOE) that was performed using several MEAs with two levels of anode platinum loading (0.05 mgPt/cm2 and 0.1 mgPt/cm2) and two different materials for platinum carbon support (Highly Graphitized Carbon and High Surface Area Carbon). Contamination testing for each MEA design configuration was performed at four different CO impurity levels (0.1 ppm, 0.2 ppm, 0.3 ppm, and 0.4 ppm) and three current densities (0.1 A/cm2, 1.0 A/cm2, and 1.7 A/cm2) at each impurity level. The results indicate that the most significant factor to improve MEA tolerance to CO contamination was the choice of carbon support. The use of high surface area carbon had an even greater impact than the use of higher Pt loading, which suggests paths toward addressing CO contamination that avoid higher catalyst cost.

Comparing Mitigation Techniques for Effective CO Mitigation in a Polymer Electrolyte Fuel Cell

The presence of carbon monoxide impurities in hydrogen can be a major deterrent to polymer electrolyte fuel cell (PEFC) performance. CO molecules present in hydrogen fuel rapidly get adsorbed on the platinum (Pt) active sites at the anode electrode and deactivate the surface reactions responsible for hydrogen oxidation [1]. On the other hand, obtaining 99.999% hydrogen purity requires major purification processes driving up the cost of hydrogen fuel [2]. To realise an economical hydrogen fuel price for fuel cell applications, reformate hydrogen containing CO can be used along with a suitable mitigation technique to reduce the adsorption of CO on Pt surface by means of oxidation or stripping. Catalyst modifications, air bleeding [3] and pulsed oxidation [4, 5] are commonly used techniques to resolve CO contamination issues in fuel cells. However, a detailed comparison of these techniques to define the efficiency as well as performance improvement in presence of CO contaminated fuel is not available. In this work, we present a comparison of results and scientific explanation of the use of various mitigation techniques to alleviate the effect of CO on the performance of a PEFC. Experiments were carried out on a single cell fuel cell at 80 ºC having modified anode catalyst (Pt/C and Pt-Ru/C) and a Pt/C cathode catalyst. CO mixed with pure hydrogen was fed to the anode and air was fed to the cathode. The cell potential was monitored when the fuel source was switched from pure hydrogen to CO doped hydrogen at a constant current density to study the impact of poisoning. Anode catalyst modification with ruthenium resulted in 200 mV increase in CO tolerance compared to platinum at a constant current density. Air bleeding in presence of Pt/C and Pt-Ru/C showed similar results in performance which caused a gradual potential loss when operated for extended periods. However, when pulsed oxidation was employed, the cell potential remained close to pure hydrogen potential ranges even for longer testing periods. Acknowledgement: This work was supported by Indian Oil Corporation (R&D) and Simon Fraser University under the SFU-IOCL joint PhD program in clean energy. [1] M. Abdollahi, J. Yu, P. K. T. Liu, R. Ciora, M. Sahimi, T. T. Tsotsis, J. Membrane Science, 390-391, 32 (2012) [2] D. Jansen, J. W. Dijkstra, R. W. van den Brink, T. A. Peters, M. Stange, R. Bredesen, A. Goldbach, H. Y. Xu, A. Gottschalk, A. Doukelis, Energy Procedia 1, 253 (2009) [3] L-Yu Sung, B-Joe Hwang, K-Lin Hsueh, W-Nien Su, C-Chung Yang, J. Power Sources 242 (2013) 264-272 [4] C.G. Farrell, C.L. Gardner and M. Ternan, J. Power Sources, 117, 282 (2007) [5] A. H. Thomason, T. R. Lalk, A. J. Appleby, J. Power Sources 135 (2004) 204-211

Heterogeneous Catalytic Reactor for Hydrogen Production from Formic Acid and Its Use in Polymer Electrolyte Fuel Cells

A proof-of-concept prototype of a heterogeneous catalytic reactor has been developed for continuous production of hydrogen via formic acid (FA) dehydrogenation. A laboratory-type polymer electrolyte fuel cell (PEFC) fed with the resulting reformate gas stream (H2 + CO2) was applied to convert chemical energy to electricity. To implement an efficient coupling of the reactor and PEFC, research efforts in interrelated areas were undertaken: (1) solid catalyst development and testing for H2 production; (2) computer modeling of heat and mass transfer to optimize the reactor design; (3) study of compatibility of the reformate gas fuel (H2 + CO2) with a PEFC; and (4) elimination of carbon monoxide impurities via preferential oxidation (PROX). During the catalyst development, immobilization of the ruthenium(II)–meta-trisulfonated triphenylphosphine, Ru-mTPPTS, catalyst on different supports was performed, and this complex, supported on phosphinated polystyrene beads, demonstrated the best results. A validated mathematical model of the catalytic reactor with coupled heat transfer, fluid flow, and chemical reactions was proposed for catalyst bed and reactor design. Measured reactor operating data and characteristics were used to refine modeling parameters. In turn, catalyst bed and reactor geometry were optimized during an iterative adaptation of the reactor and model parameters. PEFC operating conditions and fuel gas treatment/purification were optimized to provide the best PEFC efficiency and lifetime. The low CO concentration (below 5 ppm) in the reformate was ensured by a preferential oxidation (PROX) stage. Stable performance of a 100 W PEFC coupled with the developed reactor prototype was successfully demonstrated.

Atomic Layer Metal Deposition from Ethanol for Catalytic Applications

Core-shell architectures have been proven beneficial in enhancing nanocatalysts’ activity, selectivity and durability while increasing utilization of precious metals such as Pt, an expensive but highly active catalyst for various electrochemical and chemical reactions, for example the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells. In order to fully utilize benefits of this approach, a reliable synthesis method is essential to produce core-shell nanoparticles with uniform shell thickness tunable in 1 – 3 monolayer range. Usually the Pt monolayer shell is formed via electrochemical routes, such as galvanic displacement of an underpotentially deposited Cu layer.[ 1 ]Here we report a surfactant-free, ethanol-based wet chemical approach to coating metal nanoparticles with uniform Pt atomic layers with high reproducibility and scalability. The principles applied in the coating method will be illustrated with two practical examples. The first example is ordered Ru-Pt core-shell nanocatalysts with enhanced carbon monoxide (CO) tolerance and dissolution resistance for the anodic HOR in PEM fuel cells.[ 2 ] While the hydrogen produced via steam reforming followed by water gas shift reaction contains about 1% of CO which can severely deactivate the current fuel-cell catalysts, recent advances have been made in removing CO to ~ 10 ppm via preferential oxidation of CO in hydrogen feeds (PROX)[ 3 ], renewing the interest in developing CO-tolerant catalysts for using inexpensive reformates (hydrogen with CO impurity) as the fuel other than pure hydrogen. The partial alloying between Ru and Pt is avoided, and thus single crystalline particles are formed though Ru and Pt have distinctly different crystal structures, hexagonal close-packed (hcp) for Ru, and face-centered cubic (fcc) for Pt. Ordered lattice structural transition from Ru(hcp) to Pt(fcc)at the core-shell interface is verified by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM), coupled with density functional theory (DFT) calculations. Furthermore, the Ru-Pt electrocatalysts with optimized structures and improved Pt utilizations exhibit significantly enhanced CO tolerance and excellent dissolution resistance at ultra-low catalyst loadings for the HOR in fuel-cell tests. This new level of atomic control also solves the dilemma in using a dissolution-prone metal (Ru) for alleviating the deactivating effect of CO. The second example is Pt monolayer coated on Pd nanoparticles with high activities and stabilities for the ORR, the cathodic reaction in PEM fuel cells. The uniformity of Pt shells is verified by various characterization techniques, and DFT calculations also show that two-dimensional growth of Pt on Pd is energetically favorable. The as-prepared Pt monolayer electrocatalysts exhibit high electrocatalytic performance toward the ORR. In conclusion, we have demonstrated a surfactant-free and high-yield chemical route for coating of Pt atomic layers on other metal nanoparticles, which ensures high reproducibility and scalability. The strategy illustrated here could be applicable to the fabrication of other bimetallic or multimetallic core-shell nanoparticles for various applications. Acknowledgements This research was performed at Brookhaven National Laboratory (BNL) under contract DE-AC02-98CH10886 with the U.S. Department of Energy (DOE).

On-board removal of CO and other impurities in hydrogen for PEM fuel cell applications

Carbon monoxide (CO) in the hydrogen (H 2) stream can cause severe performance degradation for an H 2 polymer electrolyte membrane (PEM) fuel cell. The on-board removal of CO from an H 2 stream requires a process temperature less than 80 °C, and a fast reaction rate in order to minimize the reactor volume. At the present time, few technologies have been developed that meet these two requirements. This paper describes a concept of electrochemical water gas shift (EWGS) process to remove low concentration CO under ambient conditions for on-board applications. No on-board oxygen or air supply is needed for CO oxidation. Experimental work has been carried out to prove the concept of EWGS and the results indicate that the process can completely remove low level CO and improve the performance of a PEM fuel cell to the level of a pure H 2 stream. Because the EWGS electrolyzer can be modified from a humidifier for a PEM fuel cell system, no additional device is needed for the CO removal. More experimental data are needed to determine the rate of CO electrochemical removal and to explore the mechanism of the proposed process.

Electrocatalytic Properties of Binary Systems Based on Platinum and Palladium in the Reaction of Oxidation of Hydrogen Poisoned by Carbon Monoxide

Investigation of a number of binary systems based on platinum and palladium and synthesized on carbon black XC72 as catalysts in the reaction of electrooxidation of hydrogen and hydrogen poisoned by carbon monoxide is carried out with use made of a complex of electrochemical methods. Exchange currents of the hydrogen reaction are determined as calculated per metal weight and its surface area. The developed methods of synthesis of binary systems are shown to make it possible to produce catalysts whose activity in the reaction of electrooxidation of hydrogen is commensurate with the activity of a platinum catalyst. The maximum tolerance with respect to carbon monoxide impurities among the binary systems investigated is found to be exhibited by PtMo and PdAu. The activity of an anode based on platinum in a model fuel cell with a solid polymer electrolyte drops by 2 and 7 times in the presence of 30 and 150 ppm CO, while the observed decrease in the current for system PtMo is equal to 10 and 50%, respectively.

Hydrogen Oxidation on a Platinum Microelectrode: Effect of Carbon Monoxide Impurities

The kinetics of the hydrogen oxidation and the CO adsorption on a Pt (ultra)microelectrode is studied in a 0.5 M H2SO4 solution saturated with a mixture of gaseous H2 and CO at partial CO pressures pCO = 10–500 ppm. The balance between rates of diffusion and adsorption of CO at different adsorption times is studied. Studied is the effect of CO impurities in H2 on steady-state polarization curves for the hydrogen ionization and nonsteady-state curves of the oxidation current decay with time at 0.02–0.05 V. Conditions under which in a certain time interval and at a certain CO concentration the slope of an I vs. t curve is proportional to pCO are determined. The obtained dependence may be used when designing a technique for monitoring CO impurities in technical hydrogen.

Hydrogen separation through the use of mixed oxygen ion and electron conducting membranes (I): theoretical analysis

Membrane-based processes are becoming increasingly important in the field of industrial gas separation. Such processes are attractive from the standpoint of high separation selectivity and high conversion ratios in cases involving gas phase and gas–solid reactions. In particular, the application of dense ceramic mixed ionic and electronic conducting membranes to separate gases such as oxygen through ambipolar transport of oxygen ions and electrons and hydrogen through ambipolar transport of protons and electrons from gas mixtures at elevated temperatures (>500°C) is gaining increasing importance. As a specific example, the requirement of high-purity tonnage hydrogen with less than 10 ppm carbon monoxide impurity levels would be absolutely essential for low-temperature proton exchange membrane fuel cells to gain wide market acceptance. We analyze herein a novel membrane-based hydrogen separation process which has heretofore not been widely reported in the literature.

Low-Carbon Monoxide Hydrogen by Sorption-Enhanced Reaction

Hydrogen is an increasingly important chemical raw material and a probable future primary energy carrier. In many current and anticipated applications the carbon monoxide impurity level must be reduced to low-ppmv levels to avoid poisoning catalysts in downstream processes. Methanation is currently used to remove carbon monoxide in petroleum refining operations while preferential oxidation (PROX) is being developed for carbon monoxide control in fuel cells. Both approaches add an additional step to the multi-step hydrogen production process, and both inevitably result in hydrogen loss. The sorption enhanced process for hydrogen production, in which steam-methane reforming, water-gas shift, and carbon dioxide removal reactions occur simultaneously in the presence of a nickel-based reforming catalyst and a calcium-based carbon dioxide sorbent, is capable of producing high purity hydrogen containing minimal carbon monoxide in a single processing step. The process also has the potential for producing pure CO2 that is suitable for subsequent use or sequestration during the sorbent regeneration step. The current research on sorption-enhanced production of low-carbon monoxide hydrogen is an extension of previous research in this laboratory that proved the feasibility of producing 95+% hydrogen (dry basis), but without concern for the carbon monoxide concentration. This paper describes sorption-enhanced reaction conditions – temperature, feed gas composition, and volumetric feed rate – required to produce 95+% hydrogen containing low carbon monoxide concentrations suitable for direct use in, for example, a proton exchange membrane fuel cell.

Gold’s future role in fuel cell systems

Innovative recent research has suggested that gold-based catalysts are potentially capable of being effectively employed in fuel cells and related hydrogen fuel processing. The justification for developing the gold catalyst technologies described, is not only based on their promising technical performance, but also the relatively low stable price and greater availability of gold compared with the platinum group metals. The employment of gold catalysts could therefore produce a welcome reduction in the capital cost of fuel cell installations. The most likely first use for gold catalysts is for the removal of carbon monoxide impurities from the hydrogen feedstock streams used for fuel cells. Such hydrogen is usually obtained from reforming reactions (from hydrocarbons or methanol) either from free-standing plant or from an on-board reformer in a vehicle in the case of transport applications. Absence of carbon monoxide would enable fuel cells to run at lower temperatures and with improved efficiency. Effectiveness of gold catalysts in this application has already been demonstrated. Preferential oxidation (PROX) of carbon monoxide in hydrogen-rich reformer gas is best effected by a gold catalyst (Au/α-Fe 2O 3) which is significantly more active at lower temperatures than the commercial PROX catalyst, i.e. Pt/γ-Al 2O 3 currently used for this purpose. Supported gold catalysts are also very active in the water gas shift reaction used for producing hydrogen from carbon monoxide and water. Research has shown that gold supported on iron oxide (Au/α-Fe 2O 3) catalyst is more active at lower temperatures than both the α-Fe 2O 3 support and the mixed copper/zinc oxide (CuO/ZnO) catalyst currently used commercially. Preparation of gold on iron oxide and gold on titania (Au/Fe 2O 3 and Au/TiO 2) by deposition–precipitation produces more active catalysts than by conventional co-precipitation. Other applications for gold in fuel cells are described and include its use as a corrosion resistant material and the incorporation of gold catalysts to provide useful improvements in electrode conductivity.

Improved APIMS Methods: I . Analysis of Nonstandard Contaminants in Nitrogen and Argon

A single quadrupole atmospheric pressure ionization mass spectrometer (APIMS) has been used to develop new techniques for quantitative analysis of impurities in ultrahigh purity nitrogen and argon used in the manufacture of high density integrated circuits. These new techniques allow use of such an instrument for applications which have not been previously documented. The simultaneous analysis of nitrogen and carbon monoxide impurities in ultrapure argon is accomplished by taking advantage of APIMS spectral differences at m/e values other than 28. Argon impurity levels in nitrogen have also been analyzed by APIMS despite the fact that argon has a higher ionization potential than nitrogen. A quantitative analysis technique for carbon monoxide impurity in nitrogen has also been developed for APIMS which relies on simple data analysis techniques.

Electron-Bombardment Desorption of Carbon Monoxide Adsorbed on Tungsten

The ion current produced by electron bombardment of the (211) crystal face of a W ribbon is shown to be predominantly O16+. The only impurity detected, H+, was never more than 4% of the total current even when the ribbon operated in hydrogen with a carbon monoxide impurity as low as 1%.