Mohammad Mehdi Choolaei


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My publications


Choolaei, M., Cai, Q., Slade, R.C. and Horri, B.A (2018). Nanocrystalline gadolinium-doped ceria (GDC) for SOFCs by an environmentally-friendly single step method. Ceramics International, 44(11), pp.13286-13292.
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Nanocrystalline gadolinium-doped ceria (GDC) was synthesized by a single step, low cost and environmentally friendly method using ammonium tartrate as an inexpensive, green and novel precipitant. The precipitate obtained during the process was calcined at 400 and 600 °C and the effect on the final microstructural properties of the powders of differing process variables were studied. The synthesized GDC samples were analysed using a range of different techniques, including XRD, TG/DSC, FESEM, STEM, and FT-IR and Raman spectroscopies. The thermal (TG/DSC), XRD and Raman spectroscopic analyses confirm the formation of a single crystalline phase with a cubic (fluorite) unit cell and formed at a low calcination temperature (400 °C). XRD profiles permitted estimation of crystallite sizes as < 20 nm, which was further confirmed by STEM and FESEM micrographs indicating the formation of quasi-spherical particles with uniform particle sizes in the range 10–30 nm. This study will aid understanding of effects of process variables on the properties of doped metal-oxide powders prepared using the carboxylate route.
Unal, I., Meisuria, S., Choolaei, M., Reina, T.R. and Horri, B.A., (2018). Synthesis and characteristics of nanocrystalline Ni1− xCoxO/GDC powder as a methane reforming catalyst for SOFCs. Ceramics International, 44(6), pp.6851-6860.
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This paper has described the application of nickel-doped catalytic constituents based on gadolinium-doped ceria (GDC) for fabrication of the solid-oxide fuel cell (SOFC) anode layer integrated with an in-situ methane-reforming layer (MRL). Nanocrystalline powders of Ni1−xCo3xO1+3×/GDC and Ni1−xCuxO/GDC with various compositions (x = 0.3, 0.5, 0.7) were synthesized using an ultrasound-assisted method followed by a thermal treatment to be applied for fabrication of the integrated MRL and the SOFC anode layer, respectively. Thermogravimetric analysis showed that the synthesized powders should be optimally calcined at 700 °C to exhibit improved crystallinity and catalytic activity. The morphological analysis showed the formation of nanocrystalline powders with particle size ranging from 4 to 86 nm that was confirmed by the crystal size analysis using XRD results. The elemental analysis by EDX indicated a successful distribution of the constituent ceramic and bimetallic phases after the addition of a sonication stage. The results of FT-IR and Raman spectroscopy confirmed lack of solvents residual after calcination that was in agreement with residual moisture content values obtained from TGA data. The fabricated anode-MRL bilayers had an adequate porosity (36.7%) and shrinkage (33.5%) after adding carbon particles as a pore former (at a loading fraction of 5.9 wt%). The catalytic performance measurements of the MRL showed a methane conversion of 13% at maximum activity with a weight hour space velocity (WHSV) of 60 L/gh that was mainly due to carbon deposition in the reaction condition.
Horri, B.A., Choolaei, M., Chaudhry, A. and Qaalib, H. (2018). A highly efficient hydrogen generation electrolysis system using alkaline zinc hydroxide solution. International Journal of Hydrogen Energy.
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Alkaline water electrolysis is a well-established conventional technique for hydrogen production. However, due to its relatively high energy consumption, the cost of hydrogenproduced by this technique is still high. Here in this work, we report for the first time the application of alkaline zinc hydroxide solution (composed of sodium zincate and potassium zincate in NaOH and KOH solutions, respectively) as an efficient, simple and recursive electrolyte for producing clean hydrogen through a continuous dual-step electrolysis process. The ionic conductivity, electrodes current density, and hydrogen evolution rate were measured in a wide range of the electrolyte concentrations (0.1–0.59 M). Also, the cell efficiency was studied at different ranges of current density (0.09–0.25 A/cm2) and applied potential (1.8–2.2 V). Results indicated that the application of alkaline zinc hydroxide solution at the optimum electrolyte concentration can enhance the hydrogen evolution rate minimally by a factor of 2.74 (using sodium zincate) and 1.47 (using potassium zincate) compared to the conventional alkaline water electrolysers. The results of this study could be helpful to better understand the electrochemical behaviour of the alkaline water electrolysers when sodium zincate and potassium zincate are used as ionic activators for enhancing hydrogen evolution.
Nouralishahi, A., Rashidi, A.M., Mortazavi, Y., Khodadadi, A.A. and Choolaei, M. (2015). Enhanced methanol electro-oxidation reaction on Pt-CoOx/MWCNTs hybrid electro-catalyst. Applied Surface Science, 335, pp.55-64.
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The electro-catalytic behavior of Pt-CoOx/MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH4 as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoOx, Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of COads on Pt active sites by the participation of CoOx. Compared to Pt/MWCNTs, Pt-CoOx/MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoOx/MWCNTs, at small overpotentials. However, at higher overpotentials, the oxidation of adsorbed oxygen-containing groups controls the total rate of MOR process.
Nouralishahi, A., Khodadadi, A.A., Mortazavi, Y., Rashidi, A. and Choolaei, M. (2014). Enhanced methanol electro-oxidation activity of Pt/MWCNTs electro-catalyst using manganese oxide deposited on MWCNTs. Electrochimica Acta, 147, pp.192-200
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Electro-oxidation of methanol on platinum nanoparticles supported on a nanocomposite of manganese oxide (MnOx) and multi-wall carbon nanotubes (MWCNTs) is investigated. The morphology, structure, and chemical composition of the electro-catalysts are characterized by TEM, XRD, EDS, TGA, and H2-TPR. The electro-catalytic properties of electrodes are examined by cyclic voltammetry, CO-stripping, electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). Compared to Pt/MWCNTs, the Pt/MnOx-MWCNTs electro-catalyst exhibits about 3.3 times higher forward peak current density, during cyclic voltammetry, and 4.6 times higher exchange current density in methanol electro-oxidation reaction. In addition, deposition of manganese oxide onto MWCNTs dramatically increases the electrochemical active surface area from 29.7 for Pt/MWCNTs to 89.4 m2 g−1Pt for Pt/MnOx-MWCNTs. The results of long-term cyclic voltammetry show superior stability of Pt nanoparticles upon addition of manganese oxide to the support. Furthermore, the kinetics of formation of the chemisorbed OH groups improves upon manganese oxide incorporation. This leads to a lower onset potential of COads oxidation on Pt/MnOx-MWCNTs than on Pt/MWCNTs.
Nouralishahi, A., Pahlavanzadeh, H., Choolaei, M., Esmaeili, E. and Yadegari, A. (2013). Optimal oxygen concentration strategy through an isothermal oxidative coupling of methane plug flow reactor to obtain a high yield of C 2 hydrocarbons. Korean Journal of Chemical Engineering, 30(6), pp.1213-1221.
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An optimal oxygen concentration trajectory in an isothermal OCM plug flow reactor for maximizing C2 production was determined by the algorithm of piecewise linear continuous optimal control by iterative dynamic programming (PLCOCIDP). The best performance of the reactor was obtained at 1,085 K with a yield of 53.9%; while, at its maximum value, it only reached 12.7% in case of having no control on the oxygen concentration along the reactor. Also, the effects of different parameters such as reactor temperature, contact time, and dilution ratio (N2/CH4) on the yield of C2 hydrocarbons and corresponding optimal profile of oxygen concentration were studied. The results showed an improvement of C2 production at higher contact times or lower dilution ratios. Furthermore, in the process of oxidative coupling of methane, controlling oxygen concentration along the reactor was more important than controlling the reactor temperature. In addition, oxygen feeding strategy had almost no effect on the optimum temperature of the reactor. Finally, using the optimal oxygen strategy along the reactor has more effect on ethylene selectivity compared to ethane.
Choolaei, M., Rashidi, A.M., Ardjmand, M., Yadegari, A. and Soltanian, H. (2012). The effect of nanosilica on the physical properties of oil well cement. Materials Science and Engineering: A, 538, pp.288-294.
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In this research, the performance of nanoscale SiO2 in cement mortars was experimentally studied. The experimental results illustrate that the SiO2 nanostructure, which was mixed with the cement mortars was highly beneficial in improving the rheological properties of drilling cement slurry, concurrently producing an increase in the compressive and flexural strengths of the cement mortar. In addition, there was no free water found in the designed slurries using nanosilica. Results indicated that by using this nanosilica, the setting time and the length of the dormant period were decreased. Also, studying the porosity of cements designed using nanosilica showed a decrease in cement porosity as the amount of nanosilica was increased in the investigated slurries. Moreover, cements designed by using these silica nanostructures had the lowest permeability among all examined ones, which were designed utilizing other methods.
Nouralishahi, A., Mortazavi, Y., Khodadadi, A.A., Choolaei, M., Thompson, L.T. and Horri, B.A. (2017). Characteristics and Performance of Urea Modified Pt-MWCNTs for Electro-Oxidation of Methanol. Applied Surface Science.
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Multiwall carbon nanotubes are modified by urea (MWCNTs-U), as an amide group, through a simple amination method to be used as support for Pt nanoparticles in methanol electrooxidation reaction (MOR). The amination method involves a covalent grafting of urea molecules onto the surface of acid treated multiwall carbon nanotubes (MWCNTs-A) using O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU) as the coupling agent. Platinum nanoparticles are impregnated on the surface of MWCNTs-U using NaBH4. Pt/MWCNTs-U shows an enhanced electrocatalytic activity and durability with exposing larger accessible surface area and 27% higher active surface area compared to Pt/MWCNTs-A. In addition, urea incorporation can improve the electrocatalyst tolerance against CO-poisoning, due to the enhanced formation kinetics of the chemisorbed hydroxyl groups. The onset potential of COads oxidation indicates a decrease from 553 mV to 530 mV for Pt/MWCNTs-A and Pt/MWCNTs-U, respectively. It is observed that in the presence of amide group the forward peak current density and exchange current density, in CV and LSV experiments, respectively increase from 378 to 515 mA/mgPt and 1.59 × 10−8 A/cm2 to 2.12 × 10−8 A/cm2. These results are also in a good agreement with the theoretical activation energies obtained from Arrhenius plots, indicating a decrease from 41.7 to 38.8 kJ/mol methanol in the case of Pt/MWCNTs-A and Pt/MWCNTs-U, respectively.