Electrodeposition Of NiMoP For Electrocatalytic Hydrogenation Reduction Of Indigo

Indigo is the one of the most widely used vat dyes.Sodium dithionite（hydrosulfite:Na₂S₂O₄）is the most widely used reducing agent for industrial indigo dyeing.However,the by-products（mainly sulfite and sulfate）in waste water and odor pungent generated,which is harmful to health and environment.Therefore,catalytic hydrogenation,new reducing agents and biological reduction have been developed.But the high cost and operation standard of these methods can not replace hydrosulfite.The electrocatalytic hydrogenation（ECH）method uses electrolyzed water as the hydrogen source to reduce indigo,and its characteristics such as mild reaction conditions,low cost,no production of toxic substances and controllable reaction make it have a good application prospect.Now,the high catalytic activity and good stability of catalysts are the most crucial in electrocatalytic hydrogenation for Indigo.In general,the ECH activity of catalyst can be improved by regulating overpotential,stabling the atomic hydrogen,decreasing H₂,so as to improve the reaction efficiency.In this thesis,NiMoP catalyst was synthesized on the surface of stainless steel mesh（SSM）,Ni foam（NF）,Cu foam（Cu F）and carbon felt（CF）through electrochemical deposition for electrocatalytic hydrogenation of indigo.The NiMoP catalyst was characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy to reveal their structural properties.The activity,stability and electrochemical properties of the catalysts were investigated by linear sweep voltammetry,Tafel curve,cyclic voltammetry,electrochemical impedance spectroscopy and chronopotentiometry.The main research contents and conclusions are as follows:（1）NiMoP catalyst was successfully synthesized and optimized on SSM,NF,Cu F and CF by electrochemical deposition.The scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy results demonstrate that amorphous and different morphologies NiMoP catalysts are successfully prepared on four substrates.（2）The electrocatalytic activity of NiMoP is higher than Ni Mo,Ni P and Mo P.And the charge transfer resistance is lower than other catalysts.Among the four substrates,NiMoP/CF exhibited the best electrocatalytic activity with overpotential and Tafel slope of 93 m V and 89.7m V·dec^-1.Meanwhile,the electrochemical activity surface area of NiMoP/CF（687.5 cm~2）is also the largest than NiMoP/SSM（0.51 cm~2）,NiMoP/NF（78.5 cm~2）and NiMoP/Cu F（261cm~2）.In stability test,NiMoP/CF exhibits the best stability among NiMoP/SSM,NiMoP/NF and NiMoP/Cu F.So,NiMoP/CF has the best stability and catalytic activity.（3）In electrocatalytic hydrogenation of Indigo,the conversion efficiency and Faradic efficiency of NiMoP/CF are calculated 26.2%and 10.7%respectively,which is more than NiMoP/Cu F（15.5%,6.4%）.However,NiMoP/NF and NiMoP/SSM shows the poorest activity for electrocatalytic hydrogenation of Indigo,because of the larger pores structure and serious hydrogen evolution on electrode surface.NiMoP catalyst is also better than Ni Mo,Ni catalysts.The leuco-indigo solution obtained by NiMoP/CF was used to dye the catton,and the results were consistent with the traditional dyeing method.