| dc.description.abstract | This study uses Micro-Anode Guided Electroplating (MAGE) to deposit nickel-molybdenum alloy micropillars, and then use these micropillars as cathodes to explore the characteristics of electrolyzing water in 1.0 M KOH solution to produce hydrogen. Micro electroplating uses a plating bath containing 0.15 M nickel sulfate, 0.008~0.064 M sodium molybdate and 0.36 M sodium pyrophosphate, the distance between the micro anode and the cathode is 40 μm, and the voltage is 4.1~5.0 V for electroplating. During the process, the image is monitored by CCD , And record the plating current. The electroplating product is weighed with a precision balance to calculate the electroplating efficiency. The surface morphology of the plated micropillar was observed by SEM, the composition of EDS was detected, the composition distribution of the cross section was analyzed by EPMA, and the crystal structure was analyzed by XRD. The results showed that if electroplating in a bath containing 0.008M sodium molybdate, the voltage increased by 4.1 V At 5.0 V, the diameter of the micropillars obtained is slightly reduced (from 138.38 μm to 130.43 μm, a reduction of about 5.75%), but the Mo content in the composition increases from 28.4 to 55.4 at. %; if the voltage is at 5.0 V, the molybdenum When the sodium concentration is increased from 0.008 to 0.064 M for electroplating in the plating bath, the diameter of the resulting micropillars is also slightly reduced (from 130.43 μm to 126.35 μm, a decrease of about 1.95%), and the Mo content in the composition increases from 55.4 at.% To 69.4 at.%. The XRD pattern shows that the micropillars obtained by this process are all amorphous structures. COMSOL Multiphysics 5.2 simulates the electric field distribution during electroplating, which helps to analyze the influence of electroplating parameters on the morphology, composition and structure of the plating product.
In 1.0 M KOH aqueous solution, the hydrogen evolution reaction (HER) test of nickel-molybdenum alloy micropillars includes evaluation methods such as Tarfer slope method, cyclic voltammetry, and chronopotentiometry. The results show that the hydrogen production efficiency of the microcolumn is affected by its composition. According to the Tarver slope test, when the molybdenum content increases from 28.4 at.% to 55.4 at.%, the slope decreases from 254.37 mV/dec to 112.85 mV/dec. But when the molybdenum content increases from 55.4 at.% to 69.4 at.%, the slope rises back to 160.36 mV/dec. From the Tafer slope, it can be known that the hydrogen production is dominated by Volmer-Tafel. The results of cyclic voltammetry show that the micro-column test piece with 55.4 at.% Mo has the highest peak current density of 2418 mA/cm2 after 100 cycles. In the chronopotentiometric experiment, hydrogen was collected by drainage gas collection method at the same time. After 300 seconds of reaction, when the molybdenum content of the microcolumn was 28.4~55.4 at.%, 5.3~7.7 mL of hydrogen could be collected, and the hydrogen content was 57.6~69.4 at. After .%, the volume of hydrogen decreased from 7.7 mL to 7.0 mL; the electric quantity was calculated by chronopotentiometry to estimate the Faraday efficiency of hydrogen production. When the molybdenum content of the microcolumn was 34.2~55.4 at.%, the efficiency was 75.97~97.32%. After the molybdenum content is 57.6~69.4 at.%, the efficiency drops from 93.56%to 88.54%. Compared with the nickel-molybdenum film in the literature, the effect of hydrogen production in electrolyzed water is better. The nickel-molybdenum alloy micropillars have lower overpotential and higher exchange current density, so the hydrogen production reaction is easier to proceed. | en_US |