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

Graphical A simple ex situ wet chemical transformation method of alkali treatment was proposed to prepare Ni(OH) 2 nanostructured flowers with large specific surface areas from Ni-MOF-74. The relationship between concentration of alkali and the structure properties of corresponding Ni(OH) 2 was uncovered. As the results, the catalyst of Ni(OH) 2 -0.25 performed remarkably catalytic properties with lower potential, higher current density and excellent durability towards MOR among various samples. 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 as-obtained 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.