Renewable energy-based electrocatalytic hydrogenation of acetylene to ethylene (E-HAE) under mild conditions is an attractive substitution to the conventional energy-intensive industrial process, but is challenging due to its low Faradaic efficiency caused by competitive hydrogen evolution reaction. Herein, we report a highly efficient and selective E-HAE process at room temperature and ambient pressure over the Cu catalyst. A high Faradaic efficiency of 83.2% for ethylene with a current density of 29 mA cm−2 is reached at −0.6 V vs. the reversible hydrogen electrode. In-situ spectroscopic characterizations combined with first-principles calculations reveal that electron transfer from the Cu surface to adsorbed acetylene induces preferential adsorption and hydrogenation of the acetylene over hydrogen formation, thus enabling a highly selective E-HAE process through the electron-coupled proton transfer mechanism. This work presents a feasible route for high-efficiency ethylene production from E-HAE.

The molecular dynamic (MD) simulation and quantum chemical calculations for the adsorption of [2-(2-Henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethyl]-methylamine (HDM) and 2-(2-Henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethanol (HDE) on iron surface was studied using Materials Studio software. Molecular dynamic simulation results indicate that the imidazoline derivative molecules uses the imidazoline ring to effectively adsorb on the surface of iron, with the alkyl hydrophobic tail forming an n shape (canopy like covering) at geometry optimization and at 353 K. The n shape canopy like covering to a large extent may prevent water from coming in close contact with the Fe surface. The quantum chemical calculation based on the natural atomic charge, the frontier molecular orbital and the Fukui indices values and plots shows the active sites of the molecules to be mainly the N=C-N region in the imidazoline ring, others include the nitrogen and oxygen heteroatoms in the pendant part and the double bonded carbon atoms in the hydrophobic tail of the imidazoline derivative molecules. The quantum chemical calculations also reveal that the amine group in HDM and the hydroxyl group in HDE which is attached to the imidazoline ring do not result in a significant increase in the HOMO nor the LUMO density which can aid adsorption.HDM has a lower energy gap of 4.434 eV and 3.824 eV, a higher E HOMO of -4.273 eV and -4.152 eV and a higher global softness of 0.45 and 0.52 compared to HDE which have an energy gap of 4.476 eV and 4.084 eV, a E HOMO of -4.349 eV and -4.607 eV and a global softness of 0.45 and 0.49 at geometry optimization and at 353 K. The adsorption ability of the molecule is given as at geometry optimization HDM > HDE and at 353 K HDM > HDE. Theoretically HDM is a better inhibitor than HDE. The adsorption ability of the molecule is in line with the binding energy at the temperature studied.

ABSTRACT:The potentials of cocoa pod husk to adsorb Cu (II), Cd (II), Pb (II) and Fe (II) ions from aqueous solutions was investigated in a batch system. The effects of contact time, initial metal ion concentration and adsorbent dose on the adsorption capacity of the adsorbent were examined. The percent adsorbed increased as initial metal ion concentration, contact time and adsorbent dose was increased until equilibrium was reached. Langmuir isotherm and pseudo-second order models were used to analyse the equilibrium and kinetic experimental data respectively. Equilibrium experimental data of Cu (II), Cd (II), Pb (II) and Fe (II) adsorption onto cocoa pod fitted well to Langmuir model and the kinetic data also fitted well to the pseudo-second order model, as indicated by the correlation coefficients. The maximum sorption capacity (qmax) ranged as 4.16, 4.42, 4.69 and 4.83 mg/g for Fe (II), Cd (II), Cu (II) and Pb (II) respectively. This study demonstrated that the waste cocoa pod could be used as a potential adsorbent for toxic metals such as Cu (II), Cd (II), Pb (II) and Fe (II).

2-(2-Henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethyl]-methylamine (HDM), 2-(2-henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethanol (HDE) and 2-henicos-10-enyl-4,5-dihydro-1Himidazole (HDI) were synthesized using the solvent free microwave assisted organic synthesis method and characterized by FT-IR. The corrosion inhibition properties of these compounds on mild steel L360 in 3.5% NaCl solution were investigated by weight loss, potentiodynamic polarization, electrochemical impedance and scanning electron microscopic techniques. The synthesized inhibitors were tested at 60°C and 80°C with concentrations of 10, 50, 100, 200 and 300 ppm, respectively. The results from the study showed that the inhibition efficiency increased with increase in the concentration of the inhibitor to a maximum and decreased with rise in temperature. An adherent layer of inhibitor molecules on the surface is proposed to account for their inhibitive action in which the organic molecules adsorb on the active anodic and cathodic sites following Langmuir isotherm. The effectiveness of these inhibitors has been correlated to their chemical structures and were in the order of HDM > HDE > HDI. The values of activation energy, free energy of adsorption and heat of adsorption were also calculated to elaborate the mechanism of corrosion inhibition. The values obtained from the heat of adsorption (Q ads ) for the three inhibitors studied (HDM, HDE and HDI) are -58.53 kJ mol -1 , -103.27 kJ mol -1 and -133.67 kJ mol -1 , respectively. These negative values indicate that the adsorption of the inhibitors on the mild steel is exothermic signifying physical adsorption. The potentiodynamic polarization data show that the compounds studied are mixed type inhibitors. The surface characteristics of inhibited and uninhibited metal samples were investigated by scanning electron microscopy (SEM).

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Interaction of metal surfaces with organic molecules has a significant role in corrosion inhibition of metals and alloys. More clarification, from both experimental and computa­tional view is needed in describing the application of inhibitors for protection of metal surfaces. In this study, the surface adsorption and corrosion inhibition behavior of metol­azone, a quinazoline derivative, on mild steel in 0.02, 0.04, 0.06, and 0.08 M HCl solutions were investigated. Weight loss, potentiodynamic polarization and electrochemical impe­dance spectroscopy techniques were used. The optimum inhibition efficiencies of 75, 82 and 83 % were found by these three techniques at the optimum inhibitor concentration of 500 mg/L and 303 K. Scanning electron microscopy (SEM) was used to confirm adsorption of quinazoline derivative on the surface of the mild steel. Computational simulations were additionally used to give insights into the interaction between quinazoline inhibitor and mild steel surface. Thermodynamic parameters of mild steel corrosion showed that quinazoline derivative functions as an effective anti-corrosive agent that slows down corrosion process. Potentiodynamic polarization results revealed a mixed-type inhibitor, while the result of the adsorption study suggests that adsorption of the inhibitor on the mild steel surface obeys the physical adsorption mechanism and follows Langmuir adsorption isotherm model.

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