Alkali‐induced Transformation of Ni‐MOF into Ni(OH)₂ Nanostructured Flowers for Efficient Electrocatalytic Methanol Oxidation Reaction

Abstract

Post treatment of metal-organic frameworks (MOFs) is widely employed to develop efficient electrocatalysts with better catalytic properties. But the complex processes of post treatment generally led to the collapse of the original structures of MOFs, making the preservation of their pristine hierarchical porous structure a great challenge. Herein, we propose the strategy of alkali treatment of Ni-MOF to transform it into Ni(OH) 2 with similar morphology and enhanced electrocatalytic properties for methanol oxidation reaction (MOR). The structure and electrocatalytic properties of asobtained Ni(OH) 2 nanostructured flowers were seriously depended on the alkali concentrations. As the result, Ni(OH) 2 obtained from Ni-MOF treated by 0.25 M NaOH (noted as Ni(OH) 2 -0.25) performs 1.5 and 2.5 times larger current density than those of Ni(OH) 2 -0.025 and Ni(OH) 2 -0.5 for MOR. Moreover, the electrocatalytic process and mechanism of MOR on the catalyst of Ni(OH) 2 -0.25 are also revealed. Hence, this ex situ conversion strategy of alkali treatment for Ni-MOF uncovered the transformation of MOFs in alkaline solution and develops robust electrocatalyst for practical application of methanol fuel cells.

Fabrication of Flower-like Rhodium-Doped β-Ni(OH)2 as an Efficient Electrocatalyst for Methanol Oxidation Reaction in Alkaline Media

“…The O 1s spectrum of pure β-Ni­(OH) 2 is deconvoluted into three peaks with binding energies of 530.4, 531.3, and 532.44 eV. The peak at the binding energy of 530.4 eV is associated with the OH – groups. , The peaks at 531.3 and 532.44 eV are ascribed to defects and absorbed water, respectively, which suggests that some defects were formed on the surface of β-Ni­(OH) 2 nanoflowers , and the proportion of defects is 24%. An additional peak can be observed at 531.42 eV on the O 1s spectrum of Rh-doped β-Ni­(OH) 2 , which corresponds to Rh-OH. , Compared with pure β-Ni­(OH) 2 , the ratio of defects is larger in Rh-doped β-Ni­(OH) 2 (34%), indicating that Rh-doped β-Ni­(OH) 2 can provide more adsorption sites.…”

“…The usage of alkaline fuel cells can extend the range of electrode materials from noble metals to other transition metal and metal oxides. Therefore, the development of transition metal oxide and hydroxide electrocatalysts has attracted significant research interest. , …”

“…Therefore, the development of transition metal oxide and hydroxide electrocatalysts has attracted significant research interest. 13,14 Transition metal hydroxides are regarded as promising alternative catalysts for precious metals in DMFCs because of the lower poisoning effects and their multiple oxidation states. 15,16 Ni(OH) 2 is widely applied on the alkaline electrocatalysis due to its good stability in alkaline electrolytes.…”

Strong Ligand Stabilization Based on π‐Extension in a Series of Ruthenium Terpyridine Water Oxidation Catalysts

“… [13] In general the reaction may proceed heterogeneously or homogenously. In the former case, mainly metal oxide particles, for example, TiO 2 [ 14 , 15 ] CoO x ,[ 16 , 17 ] Ni(OH) 2 [18] or FeNiO x , [19] or surfaces are used. In the latter case, molecular catalysts, mostly transition metal complexes of nickel, [20] copper,[ 21 , 22 ] iridium,[ 23 , 24 ] and ruthenium[ 25 , 26 , 27 ] are employed to facilitate the catalysis.…”

Metal-Organic Framework Reinforced Acrylic Polymer Marine Coatings

“…MOFs are intrinsically modular in nature, which gives researchers excellent control over structure and porosity. The correct choice of an organic linker, based on the linker’s chelating ability, affinity to the metal node, strength of the metal–linker bond, and the symmetry of the moiety, has meant a wide range of MOFs ranging from 0-D quantum dots [ 13 ], 1-D nano rods [ 14 ], nano wires [ 15 ], nano belts [ 16 ], 2-D nano plates [ 17 ], nano sheets [ 18 ] and 3-D structures like clusters [ 19 ], flowers [ 20 ] etc., using different metals like Fe [ 21 ], Co [ 22 ], Zn [ 23 ], Ni [ 24 ], Mg [ 25 ], Zr [ 26 ] etc., have been obtained. However, when compared to these traditional metals, less attention has been focused on the synthesis of silver based MOF (Ag-MOF).…”