Computational models of adsorption at metal surfaces are often based on DFT and make use of the generalized gradient approximation. This likely implies the presence of sizable errors in the gas-phase energetics.Here, we take a step closer toward chemical accuracy with a semiempirical method to correct the gas-phase energetics of PBE, PW91, RPBE, and BEEF-vdW exchange−correlation functionals. The proposed two-step method is tested on a data set of 27 gas-phase molecules belonging to the carbon cycle: first, the errors are pinpointed based on formation energies, and second, the respective corrections are sequentially applied to ensure the progressive lowering of the data set's mean and maximum errors. We illustrate the benefits of the method in electrocatalysis by a substantial improvement of the calculated equilibrium and onset potentials for CO 2 reduction to CO on Au, Ag, and Cu electrodes. This suggests that fast and systematic gas-phase corrections can be devised to augment the predictive power of computational catalysis models.

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The heat of adsorption is an indicator of the strength of the interaction between an adsorbate and a solid adsorbent. This parameter can be determined from the heat released in calorimetric experiments or from the analysis of adsorption isotherms at different temperatures. The latter, called isosteric heats of adsorption, are commonly used in the characterization of materials for gas- and liquid-phase adsorption. Although the equations for the determination of isosteric heats of adsorption from the gas phase are well-known, approximate equations are frequently used for liquid-phase adsorption. We present here the rigorous equations for determining the isosteric heats of gas- and liquid-phase adsorption and their relation to the commonly used approximate equations. These equations are used to compute the isosteric heats of liquid adsorption based on the adsorption isotherms obtained from simulations for two well-defined systems, one ideal and the other nonideal. The results of using the rigorous equations are compared with those from the approximate equations. The main conclusion is that the commonly used approximate equations provide reasonable, but not perfect, estimates of the isosteric heats of liquid adsorption using only the experimental adsorption isotherms. The more accurate rigorous equations require additional information, including the heat of vaporization and, for nonideal mixtures, the heat of mixing.

It has been demonstrated that merging the inherent sorptive behavior of amorphous silica with organic groups increases the adsorption capabilities of the solid silica. However, the underlying mechanism of the adsorption process in the functionalized materials is not fully understood, limiting the possibility of designing optimal adsorbent materials for different applications; hence, the availability of complementary methods to advance in this field is of great interest. Here we present results concerning the adsorption of CO2 in amine-functionalized silica materials, by Monte Carlo simulations, providing new insight into the capture mechanism. We propose a simulation methodology for the design of postsynthesis-functionalized silica materials in which realistic model adsorbents are generated using an energy bias selection scheme for the possible grafting sites. This methodology can be applied to different materials. In this work, we evaluate a model MCM-41 for CO2 adsorption using grand canonical Monte Carlo simulations, and compared the results with available experimental data. A new methodology is presented, which allows accounting for the chemisorbed CO2 on the adsorption isotherms. The results indicate that although chemisorption is an important part of this process at low pressures, physisorption also plays a significant role in the capture of CO2 in these materials. Functionalization increases the interactions of the CO2 molecules with the surface, whereas it decreases the available space for adsorption of CO2; the overall efficiency of the improved adsorption lies on the availability of adsorption space versus stronger interactions. In addition to the adsorption isotherms, we studied the configurations of the amine chains during the adsorption process for different degrees of functionalization as well as the effect of the concentration of grafted amines on the adsorption isotherm. The overall results show that molecular simulations serve as a guide to quantify the CO2 amount that can be easily sorbed for carbon capture applications, highlighting the importance of this approach.