Unity Bond Index-quadratic Exponential Potential Research Articles

Kinetics of greenhouse gas CO2 hydrogenation over K-promoted Cu/ZnO/Cr2O3 catalyst towards sustainable aviation fuel production

In sustainable aviation fuel development, the catalytic approach for CO2 hydrogenation to methanol can introduce side reactions that can significantly influence the process efficiency and final product quality. For process intensification, modeling tools are crucial to predicate and understand the reaction pathways to improve the operating conditions or catalyst design. Herein, we propose a new microkinetic modeling approach that combines the unity bond index−quadratic exponential potential (UBI-QEP) method and the Langmuir-Hinshelwood–Hougen-Watson (LHHW) technique to examine the conversion of CO2 and H2 to methanol on a Cu(1 1 1)-dominated catalyst. For the mechanism study, the heat of adsorption values for the reaction intermediates and the activation barrier for all the elementary steps are calculated by the UBI-QEP method. The estimation of the pre-exponential parameter is done by fitting the model to the experimental data. This procedure decreases the computational time and enhances the model’s accuracy by bypassing complex theoretical calculations. To validate the model, the synthesis of methanol from CO2 and H2 is conducted over a K-promoted Cu/ZnO/Cr2O3 catalyst, using a lab-scale plug-flow fixed-bed reactor (PF-FBR). The computational results suggest that the synthesis of methanol over Cu(1 1 1)-facets preferentially follows the formate pathway, with the hydrogenation of formate acting as a rate-determining step (RDS). The validated model (R2 = 0.99) predicts an activation energy (Ea) of 63.70 kJ.mol−1 for CO2 conversion over the studied catalyst. The proposed microkinetic model can serve as a reliable tool for elucidating the role of active sites that may control the performance of a CO2 hydrogenation catalyst.

Modeling of Hydrogen Production from Catalytic Partial Oxidation of Ethanol over a Platinum–Rhodium-Supported Catalyst

With the aim of designing an onboard hydrogen production system for automotive applications, this work numerically obtained in-depth knowledge of the catalytic partial oxidation of ethanol (ECPOX). The simulation was developed based on a two-dimensional, non-isothermal, and single-channel monolithic catalyst. By combining a novel microkinetic approach with the classical Langmuir–Hinshelwood method, a surface reaction mechanism for ECPOX over platinum–rhodium coated on an alumina catalyst was formulated. The mechanism consisted of (i) partial oxidation of ethanol, (ii) oxidation of hydrogen, (iii) ethanol steam reforming, (iv) oxidation of carbon monoxide, (v) formation of acetaldehyde, (vi) formation of methane, and (vii) water–gas shift. Essential parameters, such as equilibrium constants for the adsorption process and activation energies, were estimated using transition state theory (TST) and the theory of unity bond index-quadratic exponential potential (UBI-QEP), respectively. The developed mechanism was optimized and validated against experimental data. The model predicted products produced from ECPOX (e.g., H2, CO, CO2, H2O, CH3CHO, and CH4) and the temperature profile inside the monolith channel as a function of the ethanol content and the oxygen-to-ethanol molar ratio. The hot spot position and temperature were accurately calculated by the model. The oxidation of ethanol dominated the first 7 mm of the catalyst, while steam reforming was active over the whole catalyst length. The reverse water–gas shift showed a small effect in the oxidation zone and approached equilibrium in the reforming zone. The model indicated that carbon monoxide adsorbed on the catalyst surface (CO*) was the most abundant reaction intermediate (MARI).

Methane dehydrogenation on 3d 13-atom transition-metal clusters: A density functional theory investigation combined with Spearman rank correlation analysis

The rational use of non-renewable energy sources such as methane (CH4) has been considered a promising alternative to several high-value chemicals. Therefore, there is a considerable effort to identify the main physical-chemical features for modulating CH4 dehydrogenation, in particular, at the nanoscale regime, where new effects could promote the breaking of the C–H bond. Thus, at this work, we report a theoretical investigation of the dehydrogenation of CH4 based on a step-by-step process on 3d 13-atom transition-metal (TM) clusters (TM = Fe, Co, Ni, Cu) through ab initio density functional theory calculations combined with the Spearman rank correlation analysis and the unity bond index-quadratic exponential potential (UBI-QEP) model. Our results revealed that the adsorption/interaction of CH4 and its dehydrogenated species (CH3, CH2, CH, and C) is guided by three factors, namely, (i) charge transfer from the TM13 clusters to the CHn species, (ii) enhancement of the sp-d coupling between the electronic states of the CHn species (sp-) and TM13 (d-states) systems, (iii) number of unpaired electrons in the CHn species, in which (ii) and (iii) increases by decreasing n, which is consistent with the tendency of the C atom to restore its 4-fold coordination. The H co-adsorption promotes an increasing in the adsorption/interaction energy as it promotes an enhancement of sp-d hybridization, which has a maximum for, Fe13 and Co13 and minimum for Cu13. From the Spearman correlation analysis, we identified that the effective coordination number, the Hirshfeld charge on the C atom, and the distance between the CHn and TM13 systems drive the magnitude of the adsorption energy, in particular, at the H co-adsorption regime. The thermodynamic and kinetic properties obtained via the UBI-QEP model indicates that the CH4 dehyrogenation is slightly favorable on Ni13 cluster, while kinetically CH4 dehydrogenation process would take place much easier on Ni13, Fe13, and Co13 rather than on the Cu13 cluster.

Understanding effects of Ni particle size on steam methane reforming activity by combined experimental and theoretical analysis

• Small Ni particles exhibit higher steam methane reforming activity than large ones. • The size-dependent activity of Ni catalysts is related to the surface-dependent activity. • Ni(2 1 1) is the most active surface for steam methane reforming. • Decreased Ni(2 1 1) surface fraction results in reduced Ni activity as size increases. Fundamental understanding of the size-dependent activity is essential to harness powers of the nanocatalysts. Here we report an experimental and theoretical study of the Ni particle size effect on activity of steam methane reforming (SMR) to achieve a better understanding of the size dependence of kinetic behavior at an atomic level. A kinetic study illustrated the higher forward methane turnover frequency on the smaller sized Ni particles. The size-dependent activity was well reproduced by microkinetic modeling on a truncated octahedron model with the kinetic parameters estimated by the improved unity bond index-quadratic exponential potential (UBI-QEP) and the Brønsted–Evans–Polanyi (BEP) relationship. Microkinetic modeling suggested that the size-dependent activity of Ni catalysts is associated with the surface-dependent activity. Much higher activity of Ni(2 1 1) than Ni(1 1 1) and Ni(1 0 0) accompanied by decreased Ni(2 1 1) surface fraction results in reduced Ni activity as particle size increases. The activity of Ni(1 1 1) is limited by high free energy barriers, while that of Ni(1 0 0) is limited by site blockage by C* and CH*. This work offers a feasible approach to gain insight into size-dependent activity and to aid rational catalyst design for SMR in which preparing extremely small Ni particles (≤6 nm) might be a good strategy.

Dissociative Adsorption, Dissolution, and Diffusion of Hydrogen in Liquid Metal Membranes. A Phenomenological Model

There is only limited experimental data and theoretical treatment available in the literature on hydrogen sorption and diffusion in liquid metals, in stark contrast with that in solid metals. This paper utilizes our predictive phenomenological model requiring minimal input, the Pauling Bond Valence-Modified Morse Potential (PBV-MMP) model, for estimating the thermodynamic and kinetic parameters of hydrogen solution and diffusion in liquid metals treated as quasi-crystalline. The PBV-MMP model is a refinement of the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) model for estimating the energetics of solid metal surface reactions. The sequential kinetic steps of hydrogen dissociative surface adsorption on the feed side, subsurface penetration, and atomic interstitial diffusion in the bulk, followed by these steps in reverse on the permeate side, are thus treated via the PBV-MMP model within Eyring’s transition-state theory framework, while the entropic changes are evaluated via Eyring’s free vo...

Combination of Langmuir-Hinshelwood-Hougen-Watson and microkinetic approaches for simulation of biogas dry reforming over a platinum-rhodium alumina catalyst

Dry reforming of CH4 on a platinum-rhodium alumina catalyst is selected to numerically investigate biogas reforming process. Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate expressions for dry reforming and reverse water-gas shift reactions are presented. Activation energies are estimated by combining microkinetics with the theory of unity bond index-quadratic exponential potential (UBI-QEP). Pre-exponential factors are initially obtained by using the transition state theory (TST) and optimised, later, by minimising errors between modelling and experimental data. Adsorption of CH4 on the catalyst surface is found to be the rate determining step in the range of relatively low temperature (600–770 °C), while at relatively high temperature (770–950 °C) the thermal cracking of adsorbed CH4 is the rate controlling step. Small effect of reverse water-gas shift reaction results in the ratio of H2 to CO produced less than unity for all operating conditions. The simulation shows that the dry reforming process proceeds with reaction rate far from equilibrium state. The presented mechanism is capable of predicting the dependence of biogas dry reforming activities (e.g., reactant conversions, product formations, H2 to CO ratio, and temperature profile inside the catalyst) on operating conditions (e.g., inlet temperature, heat supplied through the catalyst wall, and composition of biogas at inlet).

Combined Pauling Bond Valence-Modified Morse Potential (PBV-MMP) model for metals: thermophysical properties of liquid metals

ABSTRACTWe develop a new quasi-crystalline approach, combined Pauling Bond Valence-Modified Morse Potential (PBV-MMP), in which the Pauling’s classical relationship between bond valence (BV) and bond length (BL) is incorporated within a modified Morse Potential (MMP) description of the potential energy of interaction between two metal atoms in the bulk, along with the assumption that these interactions are limited to the nearest neighbours with a coordination number . This semi-theoretical approach only needs metal–metal bond energy for a specified valence to provide predictions. For the kinetic and diffusion steps, we utilise Eyring’s transition-state theory and free volume model to estimate entropy changes. The PBV-MMP approach for bulk liquid metals is in the spirit of Unity Bond Index-Quadratic Exponential Potential (UBI-QEP), which has been successful in predicting thermodynamics and kinetics of solid metal surface catalysed reactions. Our model reliably predicts self-diffusivity, viscosity, surface tension that agrees with experimental results for several liquid metals, including gallium.

Microkinetic Mechanisms for Partial Oxidation of Methane over Platinum and Rhodium

A systematic approach for the development of heterogeneous mechanisms is applied and evaluated for the catalytic partial oxidation of methane over platinum (Pt) and rhodium (Rh). The derived mechanisms are self-consistent and based on a reaction class-based framework comprising variational transition state theory (VTST) and two-dimensional collision theory for the calculation of pre-exponential factors with barrier heights obtained using the unity bond index–quadratic exponential potential (UBI–QEP) method. The surface chemistry is combined with a detailed chemistry for the gas phase, and the accuracy of the approach is evaluated over Pt for a wide range of stoichiometries (0.3 ≤ ϕ ≤ 4.0), pressures (2 ≤ P (bar) ≤ 16), and residence times. It is shown that the derived mechanism can reproduce experimental data with an accuracy comparable to that of the prevalent collision theory approach and without the reliance on experimental data for sticking coefficients. The derived mechanism for Rh shows encouraging ...

Variational Transition State Theory-Based Surface Chemistry for the C2H6/H2/O2/Pt System

A reaction class-based framework for the development of heterogeneous mechanisms is applied to study the (partial) oxidation of ethane over platinum. The rate parameters for the surface chemistry were derived using a systematic application of variational transition state theory (VTST) for adsorption, desorption, and Eley–Rideal reactions coupled with two-dimensional (2D) collision theory for reactions occurring on the surface. The approach removes the need for the experimental determination of surface sticking coefficients and the associated major uncertainties. The barrier heights were determined using the unity bond index–quadratic exponential potential (UBI–QEP) method. The combined gas- and surface-phase chemistry was evaluated against independent data sets obtained from three experimental configurations. The associated 18 cases cover a wide range of residence times, stoichiometries (0.1 < ϕ < 10.4), and inlet pressures (1–12 bar). The work highlights the generality of the VTST approach that is shown to outperform the customary sticking coefficient-based methods for key aspects. A sensitivity analysis highlights the importance of the O2 and CO adsorption pathways.

Reaction class-based frameworks for heterogeneous catalytic systems

A systematic and self-consistent approach is applied to study the combustion of hydrogen and syngas over platinum using coupled detailed gas phase and surface reaction mechanisms. The surface chemistry is derived using a reaction class-based framework comprising variational transition state theory (VTST), two-dimensional collision theory and the unity bond index-quadratic exponential potential for barrier heights. The latter approach is augmented by the inclusion of more accurate data, such as the heat of adsorption of CO, and VTST is used to systematically remove the need for the surface sticking coefficients associated with adsorption and desorption processes. Transition-state theory estimates for several reaction classes are produced by combining the M06 family of density functionals with the Stuttgart/Dresden effective core potential for metal atoms. The developed method reproduces experimental data with an accuracy comparable or better than the previously used collision theory approach and without the reliance on experimental parameters. The presented framework is well-suited for the efficient generation of novel heterogeneous reaction mechanisms and also serves to identify key parameters where high accuracy ab initio methods may be required. The latter is exemplified via the sensitivity of selected results to the adsorption of carbon monoxide on platinum.

Thermal chemistry of 2-halo-1-propanols on Ni(1 1 1) and Cu(1 1 1) surfaces: A UBI-QEP energetic modeling

The effect of β-halogen substitutions on the thermal chemistry of 1-propanol over Ni(111) and Cu(111) single-crystal surfaces was investigated using the method of unity bond index-quadratic exponential potential (UBI-QEP). This method was employed to investigate the energetics of the catalytic conversion routes of the ad-molecule mainly at the zero-coverage limit by calculating activation barriers and enthalpy changes for surface reactions. The alcohol molecule can be oxidized partially and totally over the Ni surface, however, the molecule is rather inactive on Cu. The β-halogen substitution makes extensive conversion of the alcohol possible on the Cu surface and changes conversion pathways on the Ni surface. It was found that halogen substitution as well as hydrogen bonding can affect the reactivity and conversion routes of the molecules on Ni and Cu surfaces. On account of energetic criteria, the predicted routes for decompositions and the TPD patterns for the surface species are in accord with the available experimental observations.

A detailed kinetic model for biogas steam reforming on Ni and catalyst deactivation due to sulfur poisoning

This paper deals with the development and validation of a detailed kinetic model for steam reforming of biogas with and without H2S. The model has 68 reactions among 8 gasphase species and 18 surface adsorbed species including the catalytic surface. The activation energies for various reactions are calculated based on unity bond index-quadratic exponential potential (UBI-QEP) method. The whole mechanism is made thermodynamically consistent by using a previously published algorithm. Sensitivity analysis is carried out to understand the influence of reaction parameters on surface coverage of sulfur. The parameters describing sticking and desorption reactions of H2S are the most sensitive ones for the formation of adsorbed sulfur. The mechanism is validated in the temperature range of 873–1200K for biogas free from H2S and 973–1173K for biogas containing 20–108ppm H2S. The model predicts that during the initial stages of poisoning sulfur coverages are high near the reactor inlet; however, as the reaction proceeds further sulfur coverages increase towards the reactor exit. In the absence of sulfur, CO and elemental hydrogen are the dominant surface adsorbed species. High temperature operation can significantly mitigate sulfur adsorption and hence the saturation sulfur coverages are lower compared to low temperature operation. Low temperature operation can lead to full deactivation of the catalyst. The model predicts saturation coverages that are comparable to experimental observation.

Micro-kinetic modeling of NH 3 decomposition on Ni and its application to solid oxide fuel cells

This paper presents a detailed surface reaction mechanism for the decomposition of NH 3 to H 2 and N 2 on a Ni surface. The mechanism is validated for temperatures ranging from 700 to 1500 K and pressures from 5.3 Pa to 100 kPa. The activation energies for various elementary steps are calculated using the unity bond index-quadratic exponential potential (UBI-QEP) method. Sensitivity analysis is carried out to study the influence of various kinetic parameters on reaction rates. The NH 3 decomposition mechanism is used to simulate SOFC button cell operating on NH 3 fuel.

Transformations of Ethylene on the Pd(111) Surface: A Density Functional Study

The chemistry of ethylene on group VIII metals is important for the petrochemical and polymer industries. Thus far, a complete first-principles-based conversion network of ethylene as a prototypical olefin system on metal surfaces is lacking. In this paper we present a comprehensive view on transformations of ethylene on Pd(111), based on density functional slab model calculations. Specifically, we characterized the thermodynamics and kinetics of C−H and C−C bond scission as well as H isomerization of a series of species C2Hx (x = 0−4). Accordingly, dehydrogenation or hydrogenation processes are favored for most species, whereas reactions involving the scission or formation of the C−C bond feature high barriers. Ethynyl (CHC) likely is the precursor of C−C bond scission. Ethylidyne is found to be located in a basin of the potential energy surface, which allows one to rationalize relevant experimental observations. In addition, we note that one should be cautious when using information on the potential energy surface obtained with the unity-bond-index quadratic-exponential-potential (UBI-QEP) method.

Surface Electronic/Atomic Structure and Activation Energy on Pt(111), Pt3Cu(111), and PtCu(111) for PEFC Cathode

Theoretical analysis of oxygen reduction reaction (ORR) on cathode Pt(111), Pt3Cu(111), and PtCu(111) surfaces in a polymer electrolyte fuel cell (PEFC) is performed to investigate the ORR mechanisms on Pt(111) and the effect of alloying. From density functional theory (DFT) calculations, we found that the difference in adsorption energy of O2 molecules on the surface has a strong relation with the number of d-electrons and the position of the d-band center of the surface Pt atoms. From the results of the activation energy calculations using the unity bond index–quadratic exponential potential (UBI-QEP) method, we show that the oxygen atom coverage on Pt(111) surface has a strong influence on the ORR activity. In addition, it was found that Pt3Cu(111) and PtCu(111) surfaces have lower coverage compared with that of Pt(111) surface, which results in the enhancement of ORR activity.

Single-Event Microkinetic Model for Fischer−Tropsch Synthesis on Iron-Based Catalysts

A single-event microkinetic (SEMK) model was developed for Fischer−Tropsch synthesis and applied to experimental data obtained on an iron-based catalyst in a temperature range from 523 to 623 K, total pressures from 0.6 to 2.1 MPa, and H2/CO inlet ratios from 2 to 6 mol/mol. The use of the single-event concept allowed a significant reduction of the number of adjustable parameters. The single-event pre-exponential factors were calculated based on statistical thermodynamics. The reaction enthalpies, as well as initial guesses for the activation energies, were obtained through the unity bond index−quadratic exponential potential (UBI-QEP) method. Ten activation energies of the kinetically relevant reaction families and four atomic chemisorption enthalpies remained as adjustable parameters, the latter corresponding to so-called catalyst descriptors. The SEMK model describes well the product distribution over a wide range of operating conditions with physically sound kinetic parameters. The reductive eliminati...

The UBI-QEP method: Mechanistic and kinetic studies of heterogeneous catalytic reactions

Applications of the unity bond index-quadratic exponential potential (UBI-QEP) method in mechanistic and kinetic studies of complex heterogeneous catalytic reactions are discussed. It is shown how UBI-QEP energetics helps to answer specific questions regarding the mechanisms of various reactions on metal surfaces. Examples of the following reactions are considered: elementary reactions of hydrogen transfer (from one carbon atom connected to the metal surface to another such atom in a different surface species), H-X bond breaking with the assistance of coadsorbed oxygen, methanol synthesis, Fischer-Tropsch synthesis, ammonia synthesis and decomposition, and partial methanol oxidation to formaldehyde. Then, examples of kinetic simulations using UBI-QEP energetics are considered for the following processes: ethane hydrogenolysis, watergas shift reaction, selective hydrogenation of acetylene in ethylene-rich mixtures, oxidative conversions of hydrogen and methane on Pt and Rh surfaces, ammonia decomposition, C1–C2 product formation in Fischer-Tropsch synthesis over cobalt, and steam reforming of methane. It is shown how the use of UBI-QEP and Monte Carlo methods makes it possible to calculate reaction parameters that depend on temperature in the equilibrium and kinetic regimes. To increase the accuracy of simulations, we added nonenergetic parameters affecting energetics at nonzero coverages: a spatial constraint on the distance between adsorbed atoms and the distance of hot atom traveling upon oxygen dissociation on metal surfaces. The UBI-QEP/Monte Carlo simulation method is illustrated by the study of molecular oxygen adsorption on single crystalline nickel surfaces. In most UBI-QEP-based mechanistic and kinetic studies of heterogeneous catalytic reactions, good agreement is observed with experimental observations, in many cases on a quantitative level. Taking into account diversity of reactions to which the method has been applied the agreement with experiments supports the efficiency of the method in solving mechanistic and kinetic problems.

Micro-Kinetic Study of Reduction of NO on Pt Group Catalysts

Catalytic reduction using CO has significant potential for the control of NOx using Pt group catalysts as CO is already present in the exhausts and Pt group catalysts have high durability in the presence of SO2 and H2O. Different reaction mechanisms are given in the literature for this reaction based on NO dissociation, -NCO formation and so on, but the exact reaction mechanism capable of capturing experimentally observed features is as yet unavailable. To determine the kinetics and reaction mechanism, we propose here an elementary reaction mechanism based on NO dissociation applicable to Pt group catalysts and simulated with CHEMKIN 4.0.2 using single and multiple PSR (Perfectly Stirred Reactor) model. The activation energies of the elementary steps are found from the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. Excellent agreement between literature experiments and our simulation results are observed for the NO-CO reaction on Pt and Rh catalysts and for the NO-CO-O2 reaction on Ir catalyst. The effect of temperature on the NO reduction activity is captured well by the model. Additionally the simulations can also point towards importance of particular reactions, selectivity to N2, effects of surface coverage, effects of residence time and catalytic surface area on NO reduction.

Microkinetic modelling of the formation of C 1 and C 2 products in the Fischer–Tropsch synthesis over cobalt catalysts

The heats of adsorption of different C 1 and C 2 molecules assumed to be present during the initial steps of the Fischer–Tropsch synthesis and activation energies for elementary steps envisioned to occur in the synthesis are calculated for Co by using the unity bond index-quadratic exponential potential (UBI-QEP) method. The preexponential factors for the elementary steps are calculated from transition-state theory, and the rate constants are calculated according to the Arrhenius equation. The activation barrier for hydrogenation of CO is found to be lower compared to hydrogen assisted dissociation of CO, which has a smaller activation barrier than direct dissociation of CO. The reaction steps with high activation barriers are eliminated. Based on this elimination two sets of elementary steps for formation of C 1 and C 2 alkenes and alkanes in the Fischer–Tropsch synthesis are established: one based on hydrogen assisted CO dissociation (carbide mechanism) and one based on CO hydrogenation (CO insertion mechanism). In addition, one mechanism of producing CO 2 from the water–gas shift reaction is proposed. The resulting mechanisms are combined and used in the microkinetic model, which are fitted to experimental results at methanation conditions ( T = 483 K or 493 K, p = 1.85 bar and H 2/CO = 10) over a Co/Al 2O 3 Fischer–Tropsch catalyst. A good tuning is obtained by adjusting the C–Co and H–Co binding strengths. The microkinetic modelling based on these assumptions indicates that CO is mainly converted through hydrogenation of CO and that C 2 compounds are mainly produced by insertion of CO into a metal–methyl bond. Thus, from the surface coverages and reaction rates predicted by the microkinetic modelling the mechanism can be further reduced to only include the CO insertion mechanism. Hydrogenation of CHO to CH 2O is found to be the rate determining initiation step, and insertion of CO into a metal–methyl bond is found to be the rate determining step for chain growth. By using the UBI-QEP method for calculation of activation energies, the activation barriers for dissociation of CO and hydrogenation of surface carbon are found to be too large for the carbide mechanisms to occur. However, experimental data or another theoretical method is necessary in order to support or disprove the calculated activation energies in this work.

The UBI-QEP method: Basic formalism and applications to chemisorption phenomena on transition metal surfaces. Chemisorption energetics

The paper reviews the state of the art in the unity bond index-quadratic exponential potential (UBI-QEP) method. Assumptions made in the framework of the method, as well as their validity and generality, are discussed. The method is based only on well-defined observable energetic and structural parameters. UBI-QEP formulas for calculating reaction energetics (the binding energies of atomic and molecular adsorbates, the reaction enthalpies, and the intrinsic activation barriers) at different surface coverages are discussed. The UBI-QEP formalism is best suited for calculations of the adsorption of atoms and diatomic molecules but also allows one to consider polyatomic molecules in the quasi-diatomic approximation. A new formalism is discussed for determining the binding energies of various polyatomic molecules without resorting to hypothetical (and largely ambiguous) bond energy partitioning schemes. Instead, this new formalism considers the total bond energy of gas-phase species, which is an observable value. This formalism is the recent advance in the method. Various examples of calculating the energetics of atomic and molecular adsorption are presented. In most cases, the agreement of calculated and experimental values is good. The UBI-QEP method makes it possible to consider uniformly various processes on metal surfaces: adsorption, dissociation, diffusion, recombination, disproportionation, and desorption. Examples of complicated UBI-QEP calculations of molecular adsorption are presented.