Thermodynamic and Kinetic Study of Carbon Dioxide Hydrogenation on the Metal-Terminated Tantalum-Carbide (111) Surface: A DFT Calculation

The need to reduce our reliance on fossil fuels and lessen the environmentally harmful effects of CO2 have encouraged investigations into CO2 hydrogenation to produce useful products. Transition metal carbides exhibit a high propensity towards CO2 activation, which makes them promising candidates as suitable catalysts for CO2 hydrogenation. Here, we have employed calculations based on the density-functional theory to investigate the reaction network for CO2 hydrogenation to product molecules on the tantalum-terminated TaC (111) surface, including two routes from either HCOOH* or HOCOH* intermediates. Detailed calculations of the reaction energies and energy barriers along multiple potential catalytic pathways, along with the exploration of all intermediates, have shown that CH4 is the predominant product yielded through a mechanism involving HCOOH, with a total exothermic reaction energy of −4.24 eV, and energy barriers between intermediates ranging from 0.126 eV to 2.224 eV. Other favorable products are CO and CH3OH, which are also produced via the HCOOH pathway, with total overall reaction energies of −2.55 and −2.10 eV, respectively. Our calculated thermodynamic and kinetic mechanisms that have identified these three predominant products of the CO2 hydrogenation catalyzed by the TaC (111) surface explain our experimental findings, in which methane, carbon monoxide, and methanol have been observed as the major reaction products

Carbon dioxide hydrogenation over the carbon-terminated niobium carbide (111) surface: a density functional theory study

Carbon dioxide (CO2) hydrogenation is an energetic process which could be made more efficient through the use of effective catalysts, for example transition metal carbides. Here, we have employed calculations based on the density functional theory (DFT) to evaluate the reaction processes of CO2 hydrogenation to methane (CH4), carbon monoxide (CO), methanol (CH3OH), formaldehyde (CH2O), and formic acid (HCOOH) over the carbon-terminated niobium carbide (111) surface. First, we have studied the adsorption geometries and energies of 25 different surface-adsorbed species, followed by calculations of all of the elementary steps in the CO2 hydrogenation process. The theoretical findings indicate that the NbC (111) surface has higher catalytic activity towards CO2 methanation, releasing 4.902 eV in energy. CO represents the second-most preferred product, followed by CH3OH, CH2O, and HCOOH, all of which have exothermic reaction energies of 4.107, 2.435, 1.090, and 0.163 eV, respectively. Except for the mechanism that goes through HCOOH to produce CH2O, all favourable hydrogenation reactions lead to desired compounds through the creation of the dihydroxycarbene (HOCOH) intermediate. Along these routes, CH3* hydrogenation to CH4* has the highest endothermic reaction energy of 3.105 eV, while CO production from HCO dehydrogenation causes the highest exothermic reaction energy of −3.049 eV. The surface-adsorbed CO2 hydrogenation intermediates have minimal effect on the electronic structure and interact only weakly with the surface. Our results are consistent with experimental observations

The effect of visual task on postural control in subjects with right and left chronic Hemiparesis (Pilot study)

Introduction: The role and importance of dual task with right hemisphere in postural control has been reported in many previous studies but the effect of visual task levels on postural control in subjects with right and left hemi paretic is not yet known. This study was aimed to compare the effect of visual tasks on postural control in individuals with left and right chronic hemiparesis. Materials and Methods: Participants were 6 rights and fourteen left hemiparesis selected by simple non probability sampling. Postural control tasks examined on force plate in different conditions; eyes open/close, visual inspection near/far, visual search near/far. Center of pressure sway parameters in this study were area, mean velocity, path length and phase plan total. All data were analyzed by SPSS, version 16. Results: The main effect of postural task were significant in all parameters, including mean velocity, path length, phase plan total except area, Also, main effect in affected side was prominently significant only at the area parameter (P ≤ 0.05). There is no significant difference in interaction of affected side with postural task except in phase plan total (P > 0.05). Conclusion: Because of no difference between visual task effect on right and left hemi paresis postural control, it can be noted that these two groups use similar strategies for doing this task. Keywords: Hemi paresis, Visual task, Postural contro

A first-principles study of CO2 hydrogenation on a Niobium-Terminated NbC (111) surface

As promising materials for the reduction of greenhouse gases, transition-metal carbides, which are highly active in the hydrogenation of CO2, are mainly considered. In this regard, the reaction mechanism of CO2 hydrogenation to useful products on the Nb-terminated NbC (111) surface is investigated by applying density functional theory calculations. The computational results display that the formation of CH4, CH3OH, and CO are more favored than other compounds, where CH4 is the dominant product. In addition, the findings from reaction energies reveal that the preferred mechanism for CO2 hydrogenation is thorough HCOOH*, where the largest exothermic reaction energy releases during the HCOOH* dissociation reaction (2.004 eV). The preferred mechanism of CO2 hydrogenation towards CH4 production is CO2*→t,c-COOH*→HCOOH*→HCO*→CH2O*→CH2OH*→CH2*→CH3*→CH4*, where CO2*→t,c-COOH*→HCOOH*→HCO*→CH2O*→CH2OH*→CH3OH* and CO2*→t,c-COOH*→CO* are also found as the favored mechanisms for CH3OH and CO productions thermodynamically, respectively. During the mentioned mechanisms, the hydrogenation of CH2O* to CH2OH* has the largest endothermic reaction energy of 1.344 eV

Thermodynamic and Kinetic Study of Carbon Dioxide Hydrogenation on the Metal-Terminated Tantalum-Carbide (111) Surface: A DFT Calculation

The need to reduce our reliance on fossil fuels and lessen the environmentally harmful effects of CO2 have encouraged investigations into CO2 hydrogenation to produce useful products. Transition metal carbides exhibit a high propensity towards CO2 activation, which makes them promising candidates as suitable catalysts for CO2 hydrogenation. Here, we have employed calculations based on the density-functional theory to investigate the reaction network for CO2 hydrogenation to product molecules on the tantalum-terminated TaC (111) surface, including two routes from either HCOOH* or HOCOH* intermediates. Detailed calculations of the reaction energies and energy barriers along multiple potential catalytic pathways, along with the exploration of all intermediates, have shown that CH4 is the predominant product yielded through a mechanism involving HCOOH, with a total exothermic reaction energy of −4.24 eV, and energy barriers between intermediates ranging from 0.126 eV to 2.224 eV. Other favorable products are CO and CH3OH, which are also produced via the HCOOH pathway, with total overall reaction energies of −2.55 and −2.10 eV, respectively. Our calculated thermodynamic and kinetic mechanisms that have identified these three predominant products of the CO2 hydrogenation catalyzed by the TaC (111) surface explain our experimental findings, in which methane, carbon monoxide, and methanol have been observed as the major reaction products