Surface Reduced CeO2 Nanowires for Direct Conversion of CO2 and Methanol to Dimethyl Carbonate: Catalytic Performance and Role of Oxygen Vacancy

Abstract

Ultralong 1D CeO 2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H 2 atmosphere, and first applied in direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH. The micro morphologies, physical parameters of nanowires were fully investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), N 2 adsorption, X-ray photoelectron spectrum (XPS), and temperature-programmed desorption of ammonia/carbon dioxide (NH 3 -TPD/CO 2 -TPD). The effects of surface oxygen vacancy and acidic/alkaline sites on the catalytic activity was explored. After reduction, the acidic/alkaline sites of CeO 2 nanowires can be dramatically improved and evidently raised the catalytic performance. CeO 2 nanowires reduced at 500 • C (CeO 2 _NW_500) exhibited notably superior activity with DMC yield of 16.85 mmol gcat −1 . Furthermore, kinetic insights of initial rate were carried out and the apparent activation energy barrier of CeO 2 _NW_500 catalyst was found to be 41.9 kJ/mol, much tiny than that of CeO 2 _NW catalyst (74.7 KJ/mol).

CO2 Conversion with Alcohols and Amines into Carbonates, Ureas, and Carbamates over CeO2 Catalyst in the Presence and Absence of 2‐Cyanopyridine

“…[35] 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 higher than that of CeO 2 in the reactions of (Eqs. [16][17][18], supporting that the combination of CeO 2 with 2-cyanopyridine can give strong base sites. [37] (16)…”

“…Various kinds of morphology of CeO 2 such as spindle, cube, octahedron, rod, and so on has been applied to the synthesis of dimethylcarbonate, [15] and the preparation conditions of CeO 2 , for example, calcination atmosphere, pre-reduction and so on has been investigated. [16] The CeO 2 supported on SiO 2 , Al 2 O 3 , and TiO 2 were also tested in the synthesis of diethylcarbonate from CO 2 and ethanol. [17] CeO 2 ÀZrO 2 solid solution has been used for the synthesis of dimethylcarbonate and diethylcarbonate.…”

Nanomaterials for Environmental Purification and Energy Conversion

“…[18]), H 2 evolution [25], and CO 2 reduction [26,27]. Six other papers focus on conventional catalysis ("dark" reactions), reporting efficient H 2 production [28,29], synthesis of ethanol and butanol [30], direct conversion of CO 2 and methanol to dimethyl carbonate [31], water purification [32], and advanced characterization of catalysts by X-ray absorption fine structure (EXAFS) spectroscopy [33]. The majority of studies have been performed with particulate catalysts (nanoparticles (NPs)), but organized nanostructures, such as nanotubes (TiO 2 /Cu x O y [18], carbon nanotubes (CNTs) [30,32]) and nanowires (CeO 2 [31]) have also been used.…”

“…Catalysts 2019, 9, x FOR PEER REVIEW 2 of 6 synthesis of ethanol and butanol [30], direct conversion of CO2 and methanol to dimethyl carbonate [31], water purification [32], and advanced characterization of catalysts by X-ray absorption fine structure (EXAFS) spectroscopy [33]. The majority of studies have been performed with particulate catalysts (nanoparticles (NPs)), but organized nanostructures, such as nanotubes (TiO2/CuxOy [18], carbon nanotubes (CNTs) [30,32]) and nanowires (CeO2 [31]) have also been used. Fu et al prepared CeO2 nanowires by the advanced solvothermal method for direct catalytic synthesis of dimethyl carbonate from CO2 and methanol [31].…”

“…The majority of studies have been performed with particulate catalysts (nanoparticles (NPs)), but organized nanostructures, such as nanotubes (TiO2/CuxOy [18], carbon nanotubes (CNTs) [30,32]) and nanowires (CeO2 [31]) have also been used. Fu et al prepared CeO2 nanowires by the advanced solvothermal method for direct catalytic synthesis of dimethyl carbonate from CO2 and methanol [31]. They found that the surface reduction under H2 atmosphere formed acidic/alkaline sites on the catalyst surface, and thus significantly improved catalytic activity, reducing the activation energy barrier from 74.7 to 41.9 kJ/mol.…”