| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 94 === Various Ni-P alloy coatings were electroplated from nickel citric baths, with emphasis on the composition of the solution and the electroplating current density. Hydrogen evolution reaction of the deposits in acid electrolytes at different temperatures was systemically studied.
Experimental results show that the electrocatalytic activity of the deposit can be correlated to the composition of the solution and the electroplating current density. Ni-P deposits with improved electrocatalytic activity were made by increasing the current density, electroplating time, and solution sodium hypophosphite concentration, while immediate amounts of citric anions were added to the solution. Moreover, the deposit that absorbed more hydrogen during cathodic polarization exhibited better electrocatalytic activity, as shown in the I-t curves. Nevertheless, a saturated electrocatalytic activity was observed for the deposit with an ever-increasing hydrogen adsorption capability. The deposit phosphorus content hardly changed with the electroplating current density, whereas the electrocatalytic activity of the deposit increased with increasing electroplating current density. All deposits studied were amorphous as characterized by XRD and TEM. The electrocatalytic activity of the deposit became poor when measured in the electrolytes at higher temperatures. This is likely to be due to the formation of a surface oxide film in the high-temperature electrolyte. Finally, the electrocatalytic activity of the deposit displayed insignificant change after 10 h of cathodic polarization. This indicates that the Ni-P deposits plated from nickel citric baths had excellent corrosion resistance in acid solutions, signifying they can be the electrode for hydrogen evolution in acid electrolytes.
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