DFT study of the structure sensitivity for the adsorption of methyl, methoxy, and formate on Ni(111), Ni(100), and Ni(110) surfaces

DFT studies of hydrocarbon combustion on metal surfaces

Catalytic combustion of hydrocarbons is an important technology to produce energy. Compared to conventional flame combustion, the catalyst enables this process to operate at lower temperatures; hence, reducing the energy required for efficient combustion. The reaction and activation energies of direct combustion of hydrocarbons (CH → C + H) on a series of metal surfaces were investigated using density functional theory (DFT). The data obtained for the Ag, Au, Al, Cu, Rh, Pt, and Pd surfaces were used to investigate the validity of the Brønsted-Evans-Polanyi (BEP) and transition state scaling (TSS) relations for this reaction on these surfaces. These relations were found to be valid (R² = 0.94 for the BEP correlation and R² = 1.0 for the TSS correlation) and were therefore used to estimate the energetics of the combustion reaction on Ni, Co, and Fe surfaces. It was found that the estimated transition state and activation energies (E_TS = -69.70 eV and E_a = 1.20 eV for Ni, E_TS = -87.93 eV and E_a = 1.08 eV for Co and E_TS = -92.45 eV and E_a = 0.83 eV for Fe) are in agreement with those obtained by DFT calculations (E_TS = -69.98 eV and E_a = 1.23 eV for Ni, E_TS = -87.88 eV and E_a = 1.08 eV for Co and E_TS = -92.57 eV and E_a = 0.79 eV for Fe). Therefore, these relations can be used to predict energetics of this reaction on these surfaces without doing the time consuming transition state calculations. Also, the calculations show that the activation barrier for CH dissociation decreases in the order Ag ˃ Au ˃ Al ˃ Cu ˃ Pt ˃ Pd ˃ Ni > Co > Rh > Fe.

Highly sensitive and selective colorimetric detection of sulphide using Ag–Au nanoalloys: a DFT study

For the colorimetric detection of S, SH, cysteine, and H₂S, the sensitivity of Ag–Au nanoalloy is better than pure Ag cluster, and both of them possess high selectivity for the detection of S.

Density-functional study of the methoxy intermediates at Cu(111), Cu(110) and Cu(001) surfaces

Although the geometry of the methoxy intermediates on copper surfaces has been investigated in a number of experimental and also in several theoretical papers, the situation remains controversial for the (110) and (001) surface orientations. In the present study, we perform density-functional calculations for the Cu(111), (110) and (001) surfaces. The stress is laid upon the models and ideas proposed in the literature. At the (111) face, the fcc three-fold adsorption site is found to be slightly more favourable than the hcp one. At the (110) surface, we predict the methoxy to adsorb close to the short-bridge site in a tilted geometry. Metastable long-bridge positions are less stable by more than 0.3 eV. Since for coverages up to θ = 0.5 the interaction between the methoxy groups is weak, we see no reason for the presence of two different adsorbed methoxy forms unless the copper surface is reconstructed. For the (001) surface we obtain almost the same adsorption energy for the upright adsorbed methoxy in the hollow site, and a tilted methoxy form in a position between the bridge and the hollow site. The calculations agree semiquantitatively with the available experimental data, and admit the presence of two distinct methoxy surface forms.