Carbon Monoxide Adsorption Energy Research Articles

Exploring Carbon Monoxide and Carbon Dioxide Adsorption on (5,5) Aluminum Nitride Nanotubes for Enhanced Sensor Applications: A DFT Study

This study examined the sensitivity of single-walled (5,5) aluminium nitride nanotubes ((5,5) AlNNTs) to carbon monoxide (CO) and carbon dioxide (CO2) gas molecules by performing DFT calculations using a hybrid functional, specifically, B3LYP (Becke’s three-parameter, Lee-Yang-Parr) exchange-correlation functional at a 6–31G* basis set. This research investigates the adsorption behavior of CO2 and CO molecules on pristine and silicon-doped aluminum nitride nanotubes (AlNNTs) and examines their implications for sensor applications. The study assesses each system’s adsorption energy, sensing potential, and recovery time to gain insights into their binding strength and practical viability. For CO2 adsorption on (5,5) AlNNT, significant adsorption energy of −24.36 kcal/mol was observed, indicating a strong binding to the nanotube surface, with a sensing potential of 8.95%. However, the slow recovery time of approximately 4.964 days may limit its real-time application. Si-(5,5) AlNNT exhibited a CO2 adsorption energy of −19.69 kcal/mol, a sensing potential of 5.40%, and a relatively short recovery time of approximately 2.978 min, making it a promising candidate for CO2 sensing. CO adsorption on (5,5) AlNNT showed an adsorption energy of −25.20 kcal/mol, a sensing potential of 9.095%, but a longer recovery time of approximately 20.130 days. Si-(5,5) AlNNT displayed a high CO adsorption energy of −20.78 kcal/mol, a sensing potential of 4.29%, and a recovery time of approximately 18.320 min. These findings provide insights into the adsorption characteristics of carbon molecules on AlNNTs, highlighting their potential for CO2 and CO sensing applications.

Getting insight into the CO tolerance over Co-modified MnSm/Ti catalyst for NH3-SCR of NOx at low temperature: Experiments and DFT studies

The existence of carbon monoxide (CO) in industrial boilers flue gas can suppress the performance of the selective catalytic reduction with NH3 (NH3-SCR) for NOx removal at low temperatures over the Mn-based catalyst, and the related mechanism is needed to be revealed for improving the NH3-SCR performance. In this work, the effects of CO on the NH3-SCR performance over MnSm/Ti catalyst were studied, and the CO tolerance of the catalyst with cobalt (Co) modification at low temperatures was evaluated. The DFT calculations were performed to reveal the mechanism for the modification of Co over the MnSm/Ti catalyst. The NOx conversion for MnSm/Ti catalyst decreased by 15.2%-21.4% at 150–300 ℃ due to the presence of CO in the NH3-SCR reaction atmosphere. After introducing Co into MnSm/Ti catalyst, the NOx conversion for MnSmCo/Ti catalyst only decreased by 8.9%-13.8% at 150–300 ℃ with the presence of CO. It was evidenced that the CO tolerance of the MnSm/Ti catalyst was enhanced with the Co modification. The characterizations of catalysts revealed that the adsorptions of NH3 and NO over the MnSm/Ti catalyst were inhibited by the presence of CO in the mixed atmosphere. Furthermore, the presence of CO in the flue gas resulted in the formation of carbonates, bicarbonates, and bridging formate on the surface of the MnSm/Ti catalysts, which would cause a decrease in the content of Mn4+ and Oα on the surface of the catalyst surface. Introducing Co into MnSm/Ti catalyst could enhance the adsorption of NH3 by forming more Lewis acid sites over the MnSmCo/Ti catalyst. The contents of Mn4+ and Oα over MnSmCo/Ti catalyst were increased via the strong electronic interaction between Co ions and Mn ions. DFT calculations proved that the adsorption of CO over the catalyst was suppressed by the modification of Co with the change of the adsorption energy of CO from −167.25 kJ/mol to −53.82 kJ/mol. Additionally, the Co modification facilitated the decomposition of the carbonate formed over the catalyst with the energy barrier of related reactions decreasing from 214.67 kJ/mol to 24.45 kJ/mol, thus improving the CO tolerance of the catalyst.

Adsorption Characteristics of Carbon Monoxide on Ag- and Au-Doped HfS2 Monolayers Based on Density Functional Theory

A large amount of power equipment works in closed or semi-closed environments for a long time. Carbon monoxide (CO) is the most prevalent discharge gas following a fault in the components. Based on the density functional theory of first principles, the adsorption behavior of CO gas molecules on intrinsic, Ag-doped and Au-doped hafnium disulfide (HfS2) monolayers was systematically studied at the atomic scale. Firstly, the intrinsic HfS2 monolayer, Ag-doped HfS2 (Ag-HfS2) monolayer and Au-doped HfS2 (Au-HfS2) monolayer, with different doping sites, were created. The structural stability, dopant charge transfer, substrate conductivity and energy band structure of different doping sites of the Ag-HfS2 and Au-HfS2 monolayer structures were calculated. The most stable doping structure was selected with which to obtain the best performance on the subsequent gas adsorption test. Then, the CO adsorption models of intrinsic HfS2, Ag-HfS2 and Au-HfS2 were constructed and geometrically optimized. The results show that the adsorption energy of the Ag-HfS2 monolayer for CO gas is −0.815 eV, which has good detection sensitivity and adsorption performance. The adsorption energy of CO on the Au-HfS2 monolayer is 2.142 eV, the adsorption cannot react spontaneously, and the detection sensitivity is low. The research content of this paper provides a theoretical basis for the design and research of gas sensing materials based on HfS2, promoting the development and application of HfS2 in gas sensing and other fields.

Controlling surface chemistry of CO reactions on Fe surface by S blocking: A first-principles and microkinetic studies

A combination of plane waves first principles approach and microkinetics are employed to study the energetic and kinetics of Fe (110) surface with adsorbates such as carbon monoxide (CO), sulfur (S) and their co-adsorption (CO+S), aiming to investigate the effect of S as an inhibiting agent in the adsorption and dissociation of CO. The structural properties as well as the adsorption energetics of these systems are calculated and analyzed. The presence of sulfur adsorbate on the iron surface is found to reduce the adsorption energy of CO on Fe (110) surface hence lowering its the sticking probability in the surrounding of the adsorbate. Results from our microkinetic model provide insights into how factors such as temperature and partial pressure can be tuned to control the reaction of CO on Fe surface. The calculated kinetic results show that CO adsorbs on the iron surface in molecular state up to 440 K, beyond this threshold temperature CO starts to dissociate into C and O atoms. The introduction of sulfur adsorbate on iron surface increases the threshold of CO dissociation temperature to 480 K emphasizing its impact on the reactivity of carbon monoxide on Fe (110) surface due to the sulfur blocking effect. Finally, we demonstrate that the range of sulfur blocking effect on controlling surface chemistry of CO reactions on Fe surface to be long ranged with respect to the simulation model adopted in this work.

CuO-decorated ZnO nanotube-based sensor for detecting CO gas: a first-principles study.

Understanding the effect of copper oxide (CuO)-decorated zinc oxide nanotube on carbon monoxide (CO) adsorption is crucial for designing a high-performance CO gas sensor. In this work, CO sensing properties of copper oxide-decorated zinc oxide (CuO-ZnO) nanotube are studied theoretically by employing first-principles density functional theory for the first time. The stability, adsorption mechanism, density of states, and change in electrical conductivity are studied. The results of calculating the adsorption energy show strong chemical adsorption of CO on CuO-ZnO nanotubes. The adsorption energy of CO on CuO-ZnO nanotube is calculated as 7.5 times higher than that on ZnO nanotube. The results of the Mulliken charge analysis reveal that electron transfer occurs from CO molecules to CuO-ZnO nanotubes. Additionally, the electrical conductivity of CuO-ZnO nanotubes significantly changes after adsorption of CO at room temperature. According to these studies, CuO-ZnO nanotube sensors can be used for the detection of CO gas. The results are in excellent agreement with the reported experimental results.

Effect of metal doping on carbon monoxide adsorption on phosphorene: A first-principles study

The effects of metal dopings on the carbon monoxide (CO) adsorption of phosphorene were investigated by the first-principles calculations. Base on the analysis of CO adsorption energy, Barder charge and density of states, it is found that six metal (Li, Al, Ni, Pd, Pt, and Au) dopings can improve the adsorption strength of CO. After CO adsorption, Li and Al doped phosphorene (bP-Li and bP-Al) undergo the indirect-to-direct bandgap transitions, while Ni and Au doped phosphorene (bP-Ni and bP-Au) undergo the magnetic-to-nonmagnetic transitions. These results imply that these six metal doped phosphorenes could be candidate materials for removing and detecting toxic CO.

Co-doped phosphorene: Enhanced sensitivity of CO gas sensing

First-principle calculation was carried out to systematically investigate carbon monoxide (CO) adsorption on pristine and cobalt (Co)-doped phosphorenes (Co-bP). Whether or not CO is adsorped, pristine phosphorene is a direct-band-gap semiconductor. However, the bandgap of Co-bP experiences direct-to-indirect transition after CO molecule adsorption, which will affect optical absorption considerably, implying that Co doping can enhance the sensitivity of phosphorene as a CO gas sensor. Moreover, Co doping can improve an adsorption energy of CO to 1.31 eV, as compared with pristine phosphorene (0.12 eV), also indicating that Co-bP is energetically favorable for CO gas sensing.

Tunability of the CO adsorption energy on a Ni/Cu surface: Site change and coverage effects.

The adsorption energy of carbon monoxide on Ni ad-islands and ultra-thin films grown on the Cu(110) surface can be finely tuned via a complex interplay among diffusion, site change mechanisms, and coverage effects. The observed features of CO desorption can be explained in terms of migration of CO molecules from Cu to Ni islands, competition between bridge and on-top adsorption sites, and repulsive lateral adsorbate-adsorbate interactions. While the CO adsorption energy on clean Cu(110) is of the order of 0.5 eV, Ni-alloying allows for its controlled, continuous tunability in the 0.98-1.15 eV range with Ni coverage. Since CO is a fundamental reactant and intermediate in many heterogeneous catalytic (electro)-conversion reactions, insight into these aspects with atomic level detail provides useful information to potentially drive applicative developments. The tunability range of the CO adsorption energy that we measure is compatible with the already observed tuning of conversion rates by Ni doping of Cu single crystal catalysts for methanol synthesis from a CO2, CO, and H2 stream under ambient pressure conditions.

Density functional theory investigation of carbon monoxide adsorption on the kaolinite (001) surface**Project supported by the Young Elite Scientist Sponsorship Program by CAST and the National Natural Science Foundation of China (Grant No. 51574296).

Carbon monoxide (CO) is a gaseous pollutant with adverse effects on human health and the environment. Kaolinite is a natural mineral resource that can be used for different applications, including that it can also be used for retention of pollutant gases. The adsorption behavior of carbon monoxide molecules on the (001) surface of kaolinite was studied systematically by using density-functional theory and supercell models for a range coverage from 0.11 to 1.0 monolayers (ML). The CO adsorbed on the three-fold hollow, two-fold bridge, and one-fold top sites of the kaolinite(001) was tilted with respect to the surface. The strongest adsorbed site of carbon monoxide on the kaolinite (001) surface is the hollow site followed by the bridge and top site. The adsorption energy of CO decreased when increasing the coverage, thus indicating the lower stability of surface adsorption due to the repulsion of neighboring CO molecules. In addition to the adsorption structures and energetics, the lattice relaxation, the electronic density of states, and the different charge distribution have been investigated for different surface coverages.

Development of Platinum-Niobium as a CO Tolerant Catalyst for PEFC Operating with CO Contaminated Hydrogen

Traditional Polymer Electrolyte Fuel Cells (PEFC) are fed with hydrogen in the anode and oxygen in the cathode. This type of fuel cell is especially attractive because of the high efficiency at low temperature. However, the use of reformate hydrogen compromise cell performance due to the presence of traces of carbon monoxide (CO). This contaminant is adsorbed on the surface of Pt, blocking the sites necessary for the hydrogen oxidation reaction. In this context, to improve the CO tolerance of fuel cell anodes, several bimetallic Pt-based catalysts have been proposed. [1] Some studies reported in the literature have suggested the use of niobium (Nb) as the second element in bimetallic catalysts. [2] Thus, this study aims at analyzing the effect of the addition of Nb to Pt in order to develop a CO tolerant catalyst. Pt3Nb/C catalyst was prepared using a modified impregnation method, [1] physically and morphologically characterized and tested electrochemically in a single fuel cell operating on the traditional Nafion® membranes at 85 oC. Figure 1 shows the ionic currents signal m/z = 44 obtained by on-line differential electrochemical mass spectrometry (DEMS) experiments, corresponding to CO2 formation. Lower CO oxidation overpotential is observed for the material with Nb, which is a consequence of the facilitated CO oxidation on Pt3Nb/C catalyst. Figures 2 and 3 show the results corresponding to performance of a single fuel cell operating on H2 or H2 + 100 ppm CO. As it can be seen, the Pt3Nb/C catalyst outperforms Pt/C 20%. The high CO tolerance of this material is usually explained by two distinct mechanisms: the bifunctional and electronic mechanisms. In the first, the Nb act as a source of oxygenated species, required for the electro-oxidation of CO to CO2 at overpotentials lower than that for pure Pt. The electronic effect can be discussed in terms of the changes of the position of the Pt 5d-band center induced by the presence of the second metal that modifies the CO adsorption energy, reducing the CO coverage on Pt, and leaving more free Pt sites available for H2 electro-oxidation. These effects will be discussed using on-line DEMS measurements and in situ X-ray absorption spectroscopy (XAS) analyses. ACKNOWLEDGEMENTS Authors thank FAPESP, CNPq and CAPES, Brazil, for the financial support. REFERENCES [1] Pereira, L. G. S., Paganin, V. A., Ticianelli, E. A. Electrochimica Acta, 54, 192 (2009). [2] Rocha, T. A., Ibanhi, F., Colmati, F., Linares, J. J., Paganin, V. A., Gonzalez, E. R. Journal of Applied Electrochemistry, 43, 817 (2013). Figure 1

Novel cathode catalyst for DMFC: Study of the density of states of oxygen adsorption using density functional theory

Platinum (Pt) is the most common cathode catalyst in Direct Methanol Fuel Cells (DMFC). However, Pt involved both in the oxidation reaction of methanol and the reduction of oxygen on the cathode side, which limits the performance of DMFCs. Therefore, this study investigates cobalt phthalocyanine (CoPc) as a potential DMFC cathode catalyst capable of inhibiting the reactivity of methanol oxidation. This study investigates the reaction mechanism and adsorption energy of oxygen molecules on Cobalt Phthalocyanine (CoPc) using the Density Functional Theory (DFT). The basis sets of semi-core pseudopotential (DSPP) and effective core potential are used to compare the geometric optimization of the Cobalt Phthalocyanine structure. The adsorption strength of molecular oxygen on the Cobalt metal center of Phthalocyanine is investigated using Partial Density of States and compared with that of Iron Phthalocyanine (FePc). Finally, the results show that the adsorption energy of carbon monoxide and methanol on the Cobalt and Iron metal centers of the Phthalocyanine complex yield low energy adsorption on CoPc. It was observed that the adsorption energy when two metal sites of CoPc and supported CoPc on tungsten atom are involved yields high energy adsorption and bond length of molecular oxygen that would lead to oxygen bond dissociation. Therefore, this study concludes that CoPc has the potential to replace Pt due to its high tolerance to methanol and carbon monoxide oxidation.

Modeling of bimetallic Pt-based electrocatalyst on extended-surface support for advanced hydrogen compression and separation

Electrochemical hydrogen compression (EHC) process can be used to purify and separate hydrogen from its mixtures. In this regards question of carbon monoxide (CO) tolerance of electrocatalyst, used in such a process (e.g., Pt), becomes extremely relevant. One of the approaches to increase CO tolerance is to add ruthenium metal to platinum electrocatalyst. Results of density functional theory modeling of CO adsorption on Pt–Ru alloy slabs and edges are presented in this paper. It was found that Pt2Ru alloy has higher CO adsorption energy difference on Ru and Pt atoms, ECO(Ru)–ECO(Pt), than that of PtRu2. Effect of contraction and stretching of support on CO adsorption was also investigated: stretching increases CO adsorption energy, while contraction has opposite effect. We also found that 110 surface and edges of electrocatalyst have higher CO adsorption energy than 111 surface. Finally, we considered an elementary nano-object of the modeled extended surface, whiskerette. Using molecular dynamics with Sutton-Chen potential, we simulated annealing of platinum whiskerette at 800 K and calculated trend of CO coverage: number of CO active sites increases with temperature, and after cooling, it does not reach the initial level.

Adsorption Mechanism of Carbon Monoxide on PtRu and PtRuMo Surfaces in the Density Functional Theory Perspective

Adsorption mechanism of carbon monoxide (CO) on PtRu and PtRuMo alloy surfaces is investigated using density functional theory (DFT). It includes evaluation of binding configuration and the adsorption strength. The results show that CO preferentially adsorbs onto the 3 fold hollow site of the PtRu-surface, while on the PtRuMo surface we observe the shift from the fcc hollow site to near the bridge site. We also note that adsorption energy of CO on the PtRuMo is stronger than that of adsorption on the PtRu surface. From the charge transfer analysis, we conclude that the stronger binding energy is caused by the more charge transferred to the surface-adsorbate bonding region brought by alloying Mo to the PtRu.

Transition from Molecule to Solid State: Reactivity of Supported Metal Clusters

The evolution of the adsorption energy of carbon monoxide (CO) molecules on palladium (Pd) clusters as function of Pd particle size from the molecular regime (less than ~100 atoms per particle) to the bulk regime has been revealed. This adsorption energy is retrieved from the residence time of CO molecules on the Pd clusters, measured by a pulsed molecular beam technique, versus temperature. Unprecedented accuracy on the determination of the particle size has been achieved here by using a regular array of metal clusters exhibiting a size dispersion down to the ultimate limit of a Poisson distribution. This allows getting rid of the convolution effects that generally occur when considering particles grown through other techniques.

Control of Carbon Monoxide (CO) from Automobile Exhaust by a Dealuminated Zeolite Supported Regenerative MnCo2O4 Catalyst

We synthesized MnCo(2)O(4) catalyst with very high porosity on the surface of dealuminated zeolite molecular sieves (DAZMS) for CO oxidation under actual automobile conditions. The MnCo(2)O(4) catalyst was selected on the basis of preliminary DFT study using the software ADF BAND. The MnCo(2)O(4) catalyst had comparatively higher CO adsorption energy and very low oxygen vacancy formation energy. The synthesized MnCo(2)O(4)/DAZMS catalyst was characterized by XRD, XRF, BET, SEM, and Confocal Microscopy. The Confocal microscopic analysis revealed that porosity of the dealuminated zeolite surface was significantly enhanced after the catalyst loading process. The completely precious metal free and DAZMS-supported catalyst exhibited excellent CO oxidation ability with renewed activity for seven months under actual automobile conditions with reference to normal and cold start conditions. The synthesized MnCo(2)O(4)/DAZMS not only exhibited surprisingly high catalytic activity for CO oxidation at a temperature resembling a cold start period but was also sufficiently stable/active under actual automobile conditions and ambient conditions containing large amounts of CO,H(2)O,CO(2), and NO(x) at 155-715 °C. These significant results revealed the flexible use of the present catalyst system for a wide variety of automobiles from a small gasoline-fuelled vehicle to a large diesel-fuelled vehicle that may produce high CO-content exhaust.

A Density Functional Theory Study on Carbon Monoxide Adsorption on Platinum–Osmium and Platinum–Ruthenium–Osmium Alloys

Periodic density functional theory calculations on carbon monoxide (CO) adsorbed atop on platinum–osmium binary alloys (PtOs2 and PtOs4) and the platinum–ruthenium–osmium tertiary alloy (PtRu2Os2) are used to elucidate the changes in the C–O and C–Pt bonds upon alloying Pt with Ru/Os atoms. As Pt is alloyed with Ru/Os atoms, the adsorbate internal bond (C–O bond) and the adsorbate–metal bond (C–Pt bond) strengthen following the substrate trends of PtOs4 > Pt > PtOs2 > PtRu2Os2 and Pt > PtOs4 > PtOs2 > PtRu2Os2, respectively. These trends are manifested by the corresponding C–O and C–Pt stretching frequencies and the CO adsorption energy variations. Here, we establish a theoretical framework based on the π-attraction σ-repulsion mechanism to explain the above results. This model correlates the charges, polarizations, and electron densities of the adsorbate CO orbitals, and the sp/d populations of the adsorbing Pt atom. For the systems studied here, the traditional theoretical model of 5σ-donation/2π*-back-donation with the metal substrate bands is not always sufficient to explain the relative C–O and C–Pt bonds strengths.

Coverage-Dependent Adsorption Energy of Carbon Monoxide on a Rhodium Nanocluster

Metal–adsorbate nanoclusters serve as useful models to study elementary catalytic and gas-sensor processes. However, little is known about their structural, energetic, and spectroscopic properties as a function of adsorbate surface coverage and structure. Here, we perform a systematic study of the adsorption of carbon monoxide (CO) on a tetra-atomic rhodium cluster to understand the coverage- and structure-dependent adsorption energy of CO as a function of CO coverage and to provide deeper insight into the metacarbonyl bond on metal nanoclusters. The coverage-dependent adsorption energy trends are rationalized with a use of a theoretical model, molecular orbital energy diagrams, electron density difference plots, molecular electrostatic potential plots, and simulated infrared spectra. Our model demonstrates that a critical parameter that determines the coverage-dependent energetics of the adsorption of CO at low coverages is the polarization of metal–metal π-bonds during the effective charge transfer, occ...

Electrocatalytic Properties of PtBi and PtPb Intermetallic Line Compounds via DFT: CO and H Adsorption

Pt intermetallic line compounds, such as with Pb and Bi, have been observed to improve dramatically the anode carbon monoxide (CO) tolerance of fuel cells for oxidation of small organic molecules. We have used density functional theory to study the CO and H adsorption on different surfaces of these line compounds. Among different surface orientations of PtPb and PtBi, we find (100)B and (110) have much lower cleavage energies and CO adsorption energies than (100)A and (001) and also much lower CO adsorption energies than Pt(111). Thus, (100)B and (110) are the surfaces most relevant to experimental observations, and the increased CO tolerance is not attributable to the (001) surface of the line compounds as assumed experimentally, because it binds CO the strongest, even more strongly than Pt(111). We also find that CO is not likely to dissociate on these materials. Finally, we correlate d-band center and CO adsorption energy for these non close-packed systems by developing a more universal form of the ori...

CO adsorption on transition metal clusters: Trends from density functional theory

This work reports for the first time the trends for carbon monoxide (CO) chemisorption on transition metal clusters present in supported metal catalysts. In particular, the energetic, structural and infrared adsorption characteristics of linearly (atop) CO adsorbed on transition metal nano-clusters of less than 10Å in size were explored. Spin-unrestricted density functional theory (DFT) calculations were employed to explore the trends of CO adsorption energy (AM–CO) and C–O vibrational frequency (νCO) for clusters composed of Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt and Au.The effects of the transition metal electronic structure onto the adsorption energy of CO and the vibrational stretching frequency of C–O, and how these chemical parameters can be correlated to the catalytic activity of transition supported metal catalysts that involve the adsorption, surface diffusion, and C–O bond dissociation elementary steps in heterogeneous catalytic surface reactions, are discussed. Our findings show that an increase of the electronic d-shell occupancy and the principal quantum number (n) in transition metals causes an increase in the vibrational stretching frequency of the C–O bond. This trend is inconsistent with the classical Blyholder model for the metal–carbonyl bond.

First principles study of carbon monoxide adsorption on zirconia-supported copper

We have calculated the adsorption energy of carbon monoxide on a monolayer of copper adsorbed on the (1 1 1) face of cubic zirconia. For the bulk oxide, we compute the structural parameters of cubic, tetragonal, and monoclinic ZrO 2 and obtain good agreement with experimental parameters. We also analyze the structural relaxation of the stoichiometric, oxidized and reduced (1 1 1) surfaces of cubic zirconia (c-ZrO 2). For adsorption of copper on stoichiometric c-ZrO 2, we find that the preferred binding site is atop the terminal oxygen atom, favored by 0.4 eV over other high symmetry sites. Charge density rearrangement reveals that adsorption on the oxide support causes a depletion of charge from the Cu d z 2 orbitals. Consequently, CO adsorption on zirconia-supported copper is significantly stronger than CO adsorption on clean c-ZrO 2 or clean Cu(1 0 0).