| 摘要: | 本研究以微陽極引導電鍍(Micro-Anode Guided Electroplating, MAGE)來析鍍鎳鉬合金微柱，隨後將這些微柱作為陰極，探討其在1.0 M KOH溶液中電解水產氫之特性。微電鍍使用含0.15 M硫酸鎳、0.008~0.064 M鉬酸鈉與0.36 M焦磷酸鈉鍍浴，微陽極與陰極之間距在40μm，電壓在4.1~5.0 V進行電鍍，過程中，以CCD監控影像，並記錄電鍍電流。析鍍產物以精密天秤秤重以計算電鍍效率。析鍍微柱以SEM觀察表面形貌、EDS檢測組成、EPMA分析橫截面之成分分布、XRD分析其晶體結構，結果顯示:若在含0.008M鉬酸鈉鍍浴中電鍍，電壓由4.1 V增至5.0 V時，所得微柱之直徑微幅縮減(由138.38 μm減至130.43 μm，縮減約5.75%)，但組成中Mo含量由28.4 增高至55.4 at. %；若在5.0 V電壓下，鉬酸鈉濃度由0.008增至0.064 M之鍍浴中電鍍，所得微柱之直徑也是微幅縮減(從130.43 μm減小至126.35 μm縮減約1.95%)，而組成中Mo含量由55.4 at.%增高至69.4 at.%。XRD圖譜顯示經本製程所得微柱均屬於非晶構造。COMSOL Multiphysics 5.2模擬電鍍時的電場分布情形，有助於理解析鍍產物的形貌、組成與結構受電鍍參數之影響。
在1.0 M KOH水溶液中，鎳鉬合金微柱之產氫反應(hydrogen evolution reaction, HER)測試，包括塔弗斜率法、循環伏安法、計時電位法等評估法。結果顯示，微柱之產氫效能受其組成影響，由塔弗斜率測試得知：當鉬含量由28.4 at.%增加至55.4 at.%，斜率由254.37 mV/dec下降至112.85 mV/dec，但鉬含量由55.4 at.%增至69.4 at.%時，斜率又回升至160.36 mV/dec，從塔弗斜率可以知道，產氫由Volmer-Tafel主導。循環伏安法之結果顯示：微柱含55.4 at.% Mo之試片，在經過100次循環後擁有最高的峰值電流密度2418 mA/cm2。在計時電位法實驗中，同時以排水集氣法收集氫氣，歷經300秒反應，微柱鉬含量在28.4~55.4 at.%時，可收集5.3~7.7 mL的氫氣，在鉬含量57.6~69.4 at.%後，氫氣體積由7.7 mL下降至7.0 mL；經由計時電位法計算電量，估計產氫之法拉第效率，微柱鉬含量在34.2~55.4 at.%時，可得到效率75.97~97.32%，在鉬含量57.6~69.4 at.%後，效率由93.56%下降至88.54%。和文獻中鎳鉬薄膜相比在電解水產氫的效果更佳，鎳鉬合金微柱的過電位更低、交換電流密度更大，因此產氫反應更容易進行。;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. |
