Ethanol Electrooxidation on Phase- and Morphology-Controlled Ni(OH)2 Microspheres

Abstract

<jats:p>The electrooxidation kinetics of ethanol is key to making direct ethanol fuel cells and electrocatalytically reforming ethanol viable technologies for a more sustainable energy conversion. In this study, the electrooxidation of ethanol was investigated on nickel hydroxide (Ni(OH)2) catalysts synthesized using a facile solvothermal method. Variations in the temperature, heating time, and the addition of oleylamine in the precursor enabled the phase and morphology control of the catalysts. X-ray diffraction and scanning electron microscopy show that the addition of oleylamine in the precursor resulted in microspheres with a high surface area, but favored the formation of β-phase Ni(OH)2. Elevated temperatures or prolonged periods of heating in a controlled environment, on the other hand, can lead to the formation of the ethanol oxidation reaction-active α-phase. Among the synthesized catalysts, the α-Ni(OH)2 microspheres with nanoflakes achieved the highest activity for ethanol oxidation with a current density of 24.4 mA cm−2 at 1.55 V (vs. RHE, reversible hydrogen electrode) in cyclic voltammetry tests and stable at 40 mA cm−2 in chronoamperometric tests at the same potential, comparatively higher than other Ni-based catalysts found in the literature. While the overpotential is beyond the useful range for direct ethanol fuel cells, it may be useful for understanding the mechanism of ethanol oxidation reactions on transition metal hydroxides at their oxidizing potential for ethanol electroreforming.</jats:p>

Synthesis of Carbon-Supported PdIrNi Catalysts and Their Performance towards Ethanol Electrooxidation

“…A current density peak could be expected at higher positive potential as was found by [54] who also found two reduction peaks in the reverse scan, one of which was due to NiOOH backward reduction to Ni(OH) 2 . A similar conclusion was obtained regarding EOR on Ni(OH) 2 microspheres by Lidasan et al [55]. A further similar conclusion about NiO was obtained by Amin et al [56].The overall oxidation current of PdIrNi/C is lower than that of Pd/C.…”

A new synthetic route for the preparation of [Os3(CO)10(μ-OH)(μ-H)] and its reaction with bis(diphenylphosphino)methane (dppm): syntheses and X-ray structures of two isomers of [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] and [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)]

“…Although [Os 3 (CO) 10 (m-OH)(m-H)] has been known for more than 50 years, relatively few studies, especially in comparison to the commercially available cluster [Os 3 (CO) 12 ], exist on its reactivity with various substrates. 5,[7][8][9][10] For example, [Os 3 (CO) 10 -(m-OH)(m-H)] reacts with HX to afford [Os 3 (CO) 10 (m-X)(m-H)] (where X ¼ Cl, Br, I, OBu n , OMe, OPh, RCO 2 ; R ¼ H, Me, CF 3 ), but when X is a non-coordinating anion as with HBF 4 , the cation [Os 3 (CO) 10 (NCMe) 2 (m-H)] + is formed when MeCN is employed as a solvent.…”

“…5,[7][8][9][10] For example, [Os 3 (CO) 10 -(m-OH)(m-H)] reacts with HX to afford [Os 3 (CO) 10 (m-X)(m-H)] (where X ¼ Cl, Br, I, OBu n , OMe, OPh, RCO 2 ; R ¼ H, Me, CF 3 ), but when X is a non-coordinating anion as with HBF 4 , the cation [Os 3 (CO) 10 (NCMe) 2 (m-H)] + is formed when MeCN is employed as a solvent. 5,7,8 The dearth of studies based on [Os 3 (CO) 10 (m-OH)(m-H)] may be attributed to the absence of an easy and high-yield synthetic route to this hydroxy cluster from the commercially available parent cluster [Os 3 (CO) 12 ]. We have developed a new synthetic route for the preparation of this hydroxyl-substituted cluster in good yield from hydrolysis of the triosmium cluster [Os 3 (CO) 10 (NCMe) 2 ]; the latter is a well-known precursor for many different Os 3 clusters and is easily prepared by treating [Os 3 (CO) 12 ] with Me 3 NO in MeCN at room temperature.…”

“…5,7,8 The dearth of studies based on [Os 3 (CO) 10 (m-OH)(m-H)] may be attributed to the absence of an easy and high-yield synthetic route to this hydroxy cluster from the commercially available parent cluster [Os 3 (CO) 12 ]. We have developed a new synthetic route for the preparation of this hydroxyl-substituted cluster in good yield from hydrolysis of the triosmium cluster [Os 3 (CO) 10 (NCMe) 2 ]; the latter is a well-known precursor for many different Os 3 clusters and is easily prepared by treating [Os 3 (CO) 12 ] with Me 3 NO in MeCN at room temperature. 11 Metal hydroxides have been investigated as catalysts in the electro-oxidation of ethanol, conversion of benzene to phenol, and hydrogenation of ethylene to ethane.…”

“…11 Metal hydroxides have been investigated as catalysts in the electro-oxidation of ethanol, conversion of benzene to phenol, and hydrogenation of ethylene to ethane. [12][13][14] In the case of the latter reaction, functionalization of the hydroxyl group in [Os 3 (CO) 10 (m-OH)(m-H)] using silica gives the graed cluster [Os 3 (CO) 10 (m-H)(m-OSi^)] whose use as a catalyst for the hydrogenation of ethylene to ethane has been reported to proceed via intact Os 3 intermediates. 14 The stability of a metal cluster is greatly enhanced during autogenous catalysis by using a bridging diphosphine ligand.…”