Carbon Monoxide Coverage Research Articles

CO and O2 Interaction with Kinked Pt Surfaces.

We investigate the chemical interaction of carbon monoxide (CO) and oxygen (O2) with kink atoms on steps of platinum crystal surfaces using a specially designed Pt curved sample. We aim at describing the fundamental stages of the CO oxidation reaction, i.e., CO-covered/poisoned stage and O-covered/active stage, at the poorly known kinked Pt facets by probing CO uptake/saturation and O2 saturation, respectively. Based on the systematic analysis that the curved surface allows, and using high-resolution X-ray photoemission, a diversity of terrace and step/kink species are straightforwardly identified and accurately quantified, defining a smooth structural and chemical variation across different crystal planes. In the CO-saturated case, we observe a preferential adsorption at step edges, where the CO coverage reaches a CO molecule per step Pt atom, significantly higher than their close-packed analogous steps with straight terrace termination. For the O-saturated surface, a significantly higher O coverage is observed in kinked planes compared to the Pt(111) surface. While the strong adsorption of CO at the kinked edges points toward a higher ignition temperature of the CO oxidation at kinks as compared to terraces, the large O coverage at steps may lead to an increased reactivity of kinked surfaces during the active stage of the CO oxidation.

Bioinspired molecule-functionalized Cu with high CO adsorption for efficient CO electroreduction to acetate.

Electrochemical reduction of carbon dioxide (CO2) or carbon monoxide (CO) to valuable multi-carbon (C2+) products like acetate is a promising approach for a sustainable energy economy. However, it is still challenging to achieve high activity and selectivity for acetate production, especially in neutral electrolytes. Herein, a bioinspired hemin/Cu hybrid catalyst was developed to enhance the surface *CO coverage for highly efficient electroreduction of CO to acetate fuels. The hemin/Cu electrocatalyst exhibits a remarkable faradaic efficiency of 45.2% for CO-to-acetate electroreduction and a high acetate partial current density of 152.3 mA cm-2. Furthermore, the developed hybrid catalyst can operate stably at 200 mA cm-2 for 14.6 hours, producing concentrated acetate aqueous solutions (0.235 M, 2.1 wt%). The results of in situ Raman spectroscopy and theoretical calculations proved that the Fe-N4 structure of hemin could enhance the CO adsorption and enrich the local concentration of CO, thereby improving C-C coupling for acetate production. In addition, compared to the unmodified Cu catalysts, the Cu catalysts functionalized with cobalt phthalocyanine with a Co-N4 structure also exhibit improved acetate performance, proving the universality of this bioinspired molecule-enhanced strategy. This work paves a new way to designing bioinspired electrolysis systems for producing specific C2+ products from CO2 or CO electroreduction.

Pb-rich Cu grain boundary sites for selective CO-to-n-propanol electroconversion

Electrochemical carbon monoxide (CO) reduction to high-energy-density fuels provides a potential way for chemical production and intermittent energy storage. As a valuable C3 species, n-propanol still suffers from a relatively low Faradaic efficiency (FE), sluggish conversion rate and poor stability. Herein, we introduce an “atomic size misfit” strategy to modulate active sites, and report a facile synthesis of a Pb-doped Cu catalyst with numerous atomic Pb-concentrated grain boundaries. Operando spectroscopy studies demonstrate that these Pb-rich Cu-grain boundary sites exhibit stable low coordination and can achieve a stronger CO adsorption for a higher surface CO coverage. Using this Pb-Cu catalyst, we achieve a CO-to-n-propanol FE (FEpropanol) of 47 ± 3% and a half-cell energy conversion efficiency (EE) of 25% in a flow cell. When applied in a membrane electrode assembly (MEA) device, a stable FEpropanol above 30% and the corresponding full-cell EE of over 16% are maintained for over 100 h with the n-propanol partial current above 300 mA (5 cm2 electrode). Furthermore, operando X-ray absorption spectroscopy and theoretical studies reveal that the structurally-flexible Pb-Cu surface can adaptively stabilize the key intermediates, which strengthens the *CO binding while maintaining the C–C coupling ability, thus promoting the CO-to-n-propanol conversion.

Experimental and numerical analysis of a catalyst layer in the membrane electrode assembly of polymer electrolyte membrane fuel cells

Fuel cells constitute an important strategy for carbon-neutral Carbon Dioxide recycling because they utilize the green hydrogen produced from renewable electrical energy. To achieve low-cost and high-performance polymer electrolyte fuel cells, reducing active metals by optimizing the cathode catalyst layer structure is crucial. In this study, we combined image analysis, numerical analysis, and electrochemical approaches to clarify the diffusion characteristics of the cathode catalyst layer in a polymer electrolyte membrane fuel cell. The structure of a catalyst-supported carbon substrate and stacked catalyst-supported carbon substrate was determined using transmission electron microscopy and focused ion-beam scanning electron microscopy. Porosity was analyzed by image analysis and torsion by numerical analysis using the random walk method. Diffusivity near the catalyst and pores was evaluated using a recently developed method by analyzing the active metal surface resistance based on the dependence of the catalyst layer resistance on carbon monoxide coverage. These analytical methods were applied to catalyst-supported carbon materials with different structures. Diffusion through the catalyst surface, carbon support, and carbon support aggregates was also analyzed; furthermore, we obtained following guidelines for improving the specifications. Larger pores and smaller flexures in the cathode catalyst layer may improve the performance of Polymer Electrolyte Membrane Fuel Cells.

Atomic-Scale Mechanism of Platinum Catalyst Restructuring under a Pressure of Reactant Gas.

Heterogeneous catalysis is key for chemical transformations. Understanding how catalysts' active sites dynamically evolve at the atomic scale under reaction conditions is a prerequisite for accurately determining catalytic mechanisms and predictably developing catalysts. We combine in situ time-dependent scanning tunneling microscopy observations and machine-learning-accelerated first-principles atomistic simulations to uncover the mechanism of restructuring of Pt catalysts under a pressure of carbon monoxide (CO). We show that a high CO coverage at a Pt step edge triggers the formation of atomic protrusions of low-coordination Pt atoms, which then detach from the step edge to create sub-nano-islands on the terraces, where under-coordinated sites are stabilized by the CO adsorbates. The fast and accurate machine-learning potential is key to enabling the exploration of tens of thousands of configurations for the CO-covered restructuring catalyst. These studies open an avenue to achieve an atomic-scale understanding of the structural dynamics of more complex metal nanoparticle catalysts under reaction conditions.

Evolution and distribution of the anode overpotential and its oscillations in a polymer electrolyte membrane fuel cell exposed to carbon monoxide

Carbon monoxide (CO) poisoning of polymer electrolyte membrane fuel cells (PEMFCs) remains a challenge for their deployment, and a deeper understanding of the spatiotemporal dynamics involved is needed to develop effective mitigation strategies. In this work, localised reference electrodes were used to measure the anode overpotential at three locations across the active area of a galvanostatically operated cell (0.3 A cm−2) exposed to 100 ppm CO/H2. The anode region closest to the inlet was poisoned more rapidly than the rest of the cell, following a sigmoidal variation, and presented a higher CO coverage. The varying CO concentration, combined with local operating conditions, had a direct impact on the distribution of CO coverage. Additionally, complex self-sustained oscillations of the cell voltage and the anode overpotential were observed and correlated with the rate of CO oxidation in the overall cell. The coexistence of a dominant mean-field coupling area closer to the anode inlet, and a dominant migration coupling region closer to the outlet was identified, consistent with reported modelling predictions for a single straight channel cell. Finally, the cell recovery with pure H2 was shown to be a faster process than the CO adsorption, which follows first-order kinetics and is affected by local conditions.

Compressive Stress and Charge Redistribution during CO Adsorption Onto Pt

Electroorganic reactions, where energy is either stored or released from chemical bonds within carbon-based molecules, are essential to help achieve a circular carbon-based economy. Central to electrochemical conversion of organic molecules is carbon monoxide (CO), which serves as both an intermediate in electrochemical CO2 reduction to hydrocarbons and electrochemical oxidation in fuel cells that operate via oxygenated hydrocarbons (e.g., ethanol, methanol). For the latter, Pt has been the predominate catalyst of choice, and substantial effort has been spent to identify the mechanistic details for complete oxidation of alcohol-based fuels. With CO conversion serving as an important if not rate-limiting step of the oxidative process, it is critical to understand the state of a catalytic surface when CO is present.The change in surface stress associated with the adsorption and oxidative stripping of CO on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO3 electrolyte.1 The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO free and CO-saturated electrolyte. Although CO adsorbs as a neutral molecule, significant compressive stress, up to -1.3 N/m, is induced in the Pt. The magnitude of the stress change correlates directly with the CO coverage, and within the detection limits of the stress measurement, is elastically reversible. Density functional theory calculations of a CO bound Pt surface indicate that charge redistribution from the first atomic layer of Pt to subsurface layers account for the observed compressive stress induced by the charge neutral adsorption of CO. A better understanding of adsorbate-induced surface stress is critical for the development of materials platforms for sensing and catalysis. References D. Raciti, K.A. Schwarz, J. Vinson, and G.R. Stafford, The Journal of Physical Chemistry C , 126, 4446-4457 (2022).

Selective CO-to-acetate electroreduction via intermediate adsorption tuning on ordered Cu–Pd sites

Electrochemical reduction of carbon monoxide (CO) has recently emerged as a potential approach for obtaining high-value, multicarbon products such as acetate, while the activity and selectivity for prodution of acetate have remained low. Herein, we develop an atomically ordered copper–palladium intermetallic compound (CuPd) composed of a high density of Cu–Pd pairs that feature as catalytic sites to enrich surface *CO coverage, stabilize ethenone as a key acetate path intermediate and inhibit the hydrogen evolution reaction, thus substantially promoting acetate formation. The CuPd electrocatalyst enables a high Faradaic efficiency of 70 ± 5% for CO-to-acetate electroreduction and a high acetate partial current density of 425 mA cm−2. Under membrane electrode assembly conditions, the CuPd electrocatalyst demonstrated a 500 h CO-to-acetate conversion at 500 mA cm−2 with a stable acetate Faradaic efficiency of ~50%. Electrocatalytic CO reduction presents a route to low-temperature acetate production, but activity and efficiency remain below practical levels. Here, the authors present an intermetallic compound with stable, atomically ordered Cu–Pd pairs that facilitates an acetate pathway and delivers 70% Faradaic efficiency at 425 mA cm−2.

Compressive Stress and Charge Redistribution during CO Adsorption onto Pt.

The change in surface stress associated with the adsorption and oxidative stripping of carbon monoxide (CO) on (111)-textured Pt is examined using the wafer curvature method in 0.1 mol/L KHCO3 electrolyte. The curvature of the Pt cantilever electrode was monitored as a function of potential in both CO-free and CO-saturated electrolytes. Although CO adsorbs as a neutral molecule, significant compressive stress, up to -1.3 N/m, is induced in the Pt. The magnitude of the stress change correlates directly with the CO coverage and, within the detection limits of the stress measurement, is elastically reversible. Density functional theory calculations of a CO-bound Pt surface indicate that charge redistribution from the first atomic layer of Pt to subsurface layers accounts for the observed compressive stress induced by the charge neutral adsorption of CO. A better understanding of adsorbate-induced surface stress is critical for the development of material platforms for sensing and catalysis.

Tailoring of Pt Island RuO2/C Catalysts by Galvanic Replacement to Achieve Superior Hydrogen Oxidation Reaction and CO Poisoning Resistance

For the commercialization of fuel cells, it is necessary to use pure hydrogen. This is because carbon monoxide (CO) present in hydrogen generated by the reformation of hydrocarbon-based fuels directly affects the fuel cell performance when Pt is used. To improve CO oxidation reactions on the Pt surface, various methods have been reported such as tuning the electronic structure of Pt to weaken the Pt–CO bond (electronic effect) and increasing the amount of the supplied oxygen species (bifunctional effect). Herein, we synthesized a Pt island RuO2/C (PiR/C) catalyst, in which Pt nanoparticles were placed like islands on RuO2 using the galvanic replacement method. PiR/C showed excellent hydrogen oxidation reaction activity despite its low Pt content. The analysis of the electronic structure of Pt confirmed that PiR/C prevents CO poisoning. Additionally, electrochemical analyses including CO stripping and CO bulk oxidation were performed. By these analyses, it is confirmed that CO was first removed at the high CO coverage on the PiR/C surface by the Eley–Rideal mechanism and further CO oxidation reactions were promoted by the Langmuir–Hinshelwood mechanism. Finally, superior CO management under the actual operating conditions of PiR/C was verified by single-cell analysis.

Effect of pressure and temperature on carbon dioxide reduction at a plasmonically active silver cathode

Carbon dioxide (CO2) reduction at a plasmonically active silver cathode was investigated by varying the pressure and temperature at multiple applied potentials under both dark and illuminated conditions to understand the mechanism of selectivity changes driven by plasmon-enhanced electrochemical conversion. CO2 partial pressures (PCO2) from 0.2 to 1 atm were studied during linear sweep voltammetry and chronoamperometry at −0.7, −0.9, and −1.1 VRHE. At a given applied overpotential the total current density increased with increasing PCO2 in both the dark and the light, but there were significant differences in the Tafel behavior between dark and illuminated conditions. The reduction of CO2 to carbon monoxide (CO) was found to have first-order behavior with respect to PCO2 at all applied potentials in both the dark and the light, likely indicating no change in the rate-determining step upon illumination. Activity for the hydrogen (H2) evolution reaction decreased with increasing PCO2 at slightly different rates in the dark and the light at each applied potential, making it unclear if light is influencing CO or H2 intermediate adsorbate coverage. Both formate and methanol production showed no dependence on PCO2 under any conditions, but the true reaction orders may be masked by the much higher activity for CO and H2 at the silver cathode. The investigation of product distribution with temperature at 14, 22, and 32∘C at −0.7, −0.9, and −1.1 VRHE in both the dark and the light demonstrated that the selectivity changes observed upon illumination are not caused by local heating of the cathode surface.

A dual-cathode study on Ag-Cu sequential CO2 electroreduction towards hydrocarbons

Electroreduction of CO2 to high value-added products such as hydrocarbons provides a promising way to create a carbon neutral circular economy. Copper (Cu) is the most effective metal catalyst with selectivity towards hydrocarbons but Cu catalyst alone generally produces hydrocarbons at low selectivity and yield. Operando surface enhanced infrared absorption spectroscopic (SEIRAS) analysis reveals that the low hydrocarbon yield is attributed to the poor ability of Cu to produce carbon monoxide (CO), which is a crucial intermediate for hydrocarbon formation. In the current study, an Ag-Cu dual-cathode CO2RR device is developed, which allows separate control of electrode potential. This dual-cathode cell shows increased hydrocarbon yield (83 % for methane and 106 % for ethylene) and a 200 mV lower onset potential for C2H4, compared to electrolysis with a single Cu cathode. The CO produced by the Ag cathode transfers to Cu and increase its CO coverage, facilitating methane formation as well as promoting CC coupling to form ethylene. This study also reveals a mismatch of optimum electrode potential between Ag and Cu, which results in compromised performance of the two components in an Ag-Cu bimetallic electrocatalyst, but poses no challenge in the dual-cathode cell. To optimize the performance of the dual-cathode cell, we propose the use of a single-pass dual-gas-diffusion-cathode reactor with enhanced mass transfer for maximum hydrocarbon production. This work verifies that splitting the complex CO2RR process into two separate steps is a feasible method to improve the overall efficiency and rate of advanced products while reducing the energy input.

Capturing the Iron Carburization Mechanisms from the Surface to Bulk

Reactive force field molecular dynamics is a powerful tool to simulate large-scale reactive events such as catalytic reactions and metallic corrosion, including the carburization or so-called metal dusting corrosion. Building on a vast set of reactive force field parameters, it aims to reduce the gap between computational and experimental observations. However, the production of different versions of reactive force field parameter sets in the past 2 decades demonstrates the challenges faced by developers when attempting to describe correctly and at the same time a broad range of environments, such as the kinetics of CO adsorption, dissociation, and carbon diffusion in iron systems. This has limited the ability of these force fields to capture the competing phenomena governing complex evolution such as the carburization of iron responsible for metal dusting corrosion. In this work, we demonstrate that it is possible to treat very different environments in an integrated way by expanding the ReaxFF parameter set, creating an environment-specific description. This approach enables us to capture both metallic surface-induced dissociation of carbon-containing gases such as carbon monoxide (CO) and atomic carbon bulk diffusion in iron systems within the same simulation setup so far unreachable with previously available force fields. Employing this extended-ReaxFF to describe a cell containing a gas mixture of carbon monoxide and argon reacting with an Fe(110) surface, we fully capture at the same time competing carburization reaction/diffusion processes on both the surface and the bulk. Analysis of the radial distribution function and charge density maps shows a variety of carbon bonds at different stages/layers, highlighting the diversity of the mechanisms captured while using our extended-ReaxFF. Interestingly, at a CO coverage higher than 0.7 monolayers, the atomic arrangement of the iron atoms is sufficiently altered to cause surface reconstruction leading to a significant increase in carbon diffusion. Moreover, we are able to observe and quantify the diffusion of Fe from the bulk toward the upper coke layer, computationally elucidating the slow but continuous coke formation reported experimentally, opening a wide range of opportunities to model various stages of iron carburization mechanisms.

Operando characterisation of the impact of carbon monoxide on PEMFC performance using isotopic labelling and gas analysis

Impurities in hydrogen can have a detrimental effect on the performance of polymer electrolyte membrane fuel cells (PEMFCs) used in automotive applications. However, the establishment of reliable threshold limits for each impurity is hampered by a lack of information on the distribution and speciation of impurities within the cell, including the impact of internal reactions and gas crossover. Here we describe a novel operando method for detailed investigation of the impact of impurities on a single cell PEMFC, using a combination of isotopic labelling and measurement of gas composition at the anode exhaust via Gas Chromatography – Methaniser with Flame Ionisation Detector (GC-Methaniser-FID) and Selected Ion Flow Tube – Mass Spectrometry (SIFT-MS). We demonstrate the utility of this approach in the study of the impact of internal air bleed on carbon monoxide (CO) poisoning, enabling quantification of the surface coverage of CO on the anode catalyst as a function of cathode back-pressure. This technique shows great promise as a diagnostic tool for the investigation of the impact of a wide range of impurities at stack level (e.g. hydrocarbons, ammonia, halogenated compounds).

Coverage-Induced Orientation Change: CO on Ir(111) Monitored by Polarization-Dependent Sum Frequency Generation Spectroscopy and Density Functional Theory.

Polarization-dependent sum frequency generation (SFG) spectroscopy was applied to study the adsorption of carbon monoxide (CO) on the well-ordered (annealed) Ir(111) single-crystal surface at various CO coverages. Coverage was adjusted by varying the substrate temperature (300–575 K) and/or gas pressure (10–7 to 1.0 mbar). Under all conditions investigated, only a single absorption band at 2038–2094 cm–1 was observed, characteristic of linearly bonded (on-top) CO. Using different polarizations, PPP and SSP spectra were acquired with a high signal-to-noise ratio, whereby tilt angles of CO on Ir(111) could be determined for the first time by SFG. It was found that not only the vibrational frequency of on-top CO but also the tilt angle was strongly coverage-dependent. The higher the coverage was, the larger the vibrational frequency and the tilt angle were. At about 0.7 ML coverage, a CO tilt angle of at least 20° was observed, which is in good agreement with density functional theory (DFT) calculations. In addition, the molecular hyperpolarizability ratio (R) of CO (at 0.13 ML in UHV) was determined to be 0.08. Based on the combined SFG/DFT results, it may change to 0.29 at 0.77 ML coverage.

Contamination of Pt Catalyst with Carbon Monoxide during Hydrogen Evolution

Effect of carbon monoxide (CO) on the hydrogen evolution reaction (HER) on Pt electrode is investigated. Electrochemical hydrogen pump (EHP) cells are exposed to CO in hydrogen (H2) on the HER electrode with pure H2 maintained in the hydrogen oxidation reaction (HOR) electrode. Cyclic voltammetry is utilized to measure carbon monoxide coverage on the catalyst surface. Chemical adsorption and desorption are the dominant mechanisms to determine CO coverage on the HER electrode; hydrogen evaluation reaction has minimal effect on the CO coverage, and CO coverage has minimal impact on the HER rate unlike the HOR.

Electron density topological and adsorbate orbital analyses of water and carbon monoxide co-adsorption on platinum.

The electron density topology of carbon monoxide (CO) on dry and hydrated platinum is evaluated under the quantum theory of atoms in molecules (QTAIM) and by adsorbate orbital approaches. The impact of water co-adsorbate on the electronic, structural, and vibrational properties of CO on Pt are modelled by periodic density functional theory (DFT). At low CO coverage, increased hydration weakens C-O bonds and strengthens C-Pt bonds, as verified by changes in bond lengths and stretching frequencies. These results are consistent with QTAIM, the 5σ donation-2π* backdonation model, and our extended π-attraction σ-repulsion model (extended π-σ model). This work links changes in the non-zero eigenvalues of the electron density Hessian at QTAIM bond critical points to changes in the π and σ C-O bonds with systematic variation of CO/H2O co-adsorbate scenarios. QTAIM invariably shows bond strengths and lengths as being negatively correlated. For atop CO on hydrated Pt, QTAIM and phenomenological models are consistent with a direct correlation between C-O bond strength and CO coverage. However, DFT modelling in the absence of hydration shows that C-O bond lengths are not negatively correlated to their stretching frequencies, in contrast to the Badger rule: When QTAIM and phenomenological models do not agree, the use of the non-zero eigenvalues of the electron density Hessian as inputs to the phenomenological models, aligns them with QTAIM. The C-O and C-Pt bond strengths of bridge and three-fold bound CO on dry and hydrated platinum are also evaluated by QTAIM and adsorbate orbital analyses.

Ethylene Selectivity in CO Electroreduction when using Cu Oxides: An In Situ ATR‐SEIRAS Study

AbstractAmong all of the known catalysts for CO2 electroreduction, copper oxide materials have the most extraordinary activity and selectivity to multi‐carbon compounds such as ethylene. However, the exact nature of the active surface is not fully understood and, thus, there have been different points of view on the origin of the remarkable catalytic properties. By using in situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS), we show that carbon monoxide (CO) binds more strongly on the surface of copper oxides than on pure metallic copper and, consequently, the prolonged population of CO, a key intermediate of CO2 reduction, is observed. The high CO coverage could be a key factor that can explain the propensity of CO2 and CO electroreduction to ethylene in general but there have been a number of controversial factors in the research field of CO2 reduction. To the best of our knowledge, this is the first report that presents direct evidence for the hypothesis relating stronger CO binding and higher CO coverage to enhanced ethylene selectivity on the copper oxide catalyst relative to metallic copper based on in situ real‐time observations. This ATR‐SEIRAS application provides general phenomenological insights into the ethylene selectivity in CO electroreduction when using a copper‐based system.

Water activation and carbon monoxide coverage effects on maximum rates for low temperature water-gas shift catalysis

Linear scaling relations and Brønsted-Evans-Polanyi (BEP) relations help to elucidate trends in activation energies and adsorption energies on different metal surfaces. In this paper, Density Functional Theory (DFT) calculations available in the literature are utilized to analyze these trends and their effect on the reactivity of transition metals for the low temperature water-gas shift reaction (CO+H2O↔CO2+H2). The importance of OCO bond formation in water-gas shift is shown for metals not limited by water dissociation. In addition, the CO binding energy is shown to be an important parameter, as CO can crowd out the free sites which participate in adsorption steps, water dissociation, and carboxyl decomposition. From these results, we propose a catalyst design strategy to combine metals that adsorb O weakly, such as Au clusters or Pt nanoparticles, with supports that exhibit strong enough interactions with oxygen to be capable of easily dissociating water.

The effects of hydrogen dilution, carbon monoxide poisoning for a Pt–Ru anode in a proton exchange membrane fuel cell

The effects of carbon monoxide (CO) poisoning and hydrogen dilution are investigated for a series of simulated reformate gases. A simple mathematical model with an internal air bleed term is proposed to understand the interaction between CO poisoning, hydrogen dilution, and the internal air bleed (IAB). According to the steady-state modeling results, the presence of nitrogen can be considered as a diluting agent for a relatively dilute H2–N2 mixture. For a CO–H2–N2 mixture, hydrogen dilution and CO poisoning “magnify” each other in their combined effect on the surface coverage of hydrogen. The beneficial effect of IAB was found to be affected by the competitive adsorption between CO and hydrogen. The steady-state surface coverage of CO is influenced by the adsorption and desorption of CO, the interaction between CO and the electro-oxidation of hydrogen, the interaction between IAB/hydrogen dilution/CO, the interaction between IAB/CO. However, the steady-state surface coverage of CO is largely determined by its own adsorption and desorption properties. Analytical solutions are also derived from the proposed mode for the transient surface coverage of hydrogen and CO. The mathematical treatment has been proved extremely effective for the understanding of the steady-state and transient behavior of the CO–H2 and CO–H2–N2 mixtures.