鎳鉬鋅合金微柱之製備及其在1 M KOH中產氫之性能

On the Preparation of NiMoZn alloy micropillars and their character of H2-generation in 1 M KOH solution

鎳基金屬為工業電解水產製氫氣的重要電極材料，近年來，新開發的鎳鋅、鎳鉬等二元合金，其陰極產氫性能更為優異。本論文目的是以微陽極導引製程（Micro-anode guided electroplating, MAGE）製備鎳鉬鋅三元合金，並探討其在鹼性溶液中的陰極產氫電化學行為。研究創意在：鎳鉬鋅合金中所含之金屬鋅，在鹼性溶液中溶蝕後，可增加合金電極產氫催化電極之表面積，增高產氫活性。另外，鎳與鉬具有協同效應，藉由改變d軌道的電子密度，從而降低金屬表面上的ΔGH，增高氫的還原催化活性。因而預期鎳鉬鋅三元合金材料微柱，應具有優越產氫活性。本研究鍍浴以硫酸鎳、鉬酸鈉、氯化鋅、焦磷酸鈉、氯化銨進行配置，施加偏壓4.2 V與固定間距35μm，透過調整不同濃度鉬酸鈉鍍浴製備微電鍍微柱，並探討合金微柱之表面形貌、化學組成、晶體結構受鍍浴組成之影響。所得鎳鉬鋅三元合金以SEM觀察表面形貌、EDS分析化學組成及XRD分析晶體結構。將這些不同之鎳鉬鋅合金微柱，浸泡至1 MKOH溶液中，以循環伏安法、Tafel極化曲線量測，探討其產氫性能之差異。當鍍浴中鉬酸鈉濃度為0.10 M，所得之微柱為Ni29.4Mo66.9Zn3.7，在Tafel曲線中有最小的Tafel斜率（76 mV/dec）與最大的交換電流密度值（2.69 mA/cm2），在循環伏安曲線中具有最大陰極電流峰值（606 mA/cm2）以及最小產氫起始電位（-0.197 V vs. RHE）。

Nickel-based metals are important materials of the electrode used in the industrial electrolysis of water to generate hydrogen gas. The purpose of this work is to prepare NiMoZn alloy microcolumns by means of microanode- guided electroplating (MAGE) process and to explore the electrochemical behavior of microcolumns in alkaline solutions to produce hydrogen gas. Facile dissolution of the Zn-component in the alkaline solution from the alloy microcolumns leads to the porous structure that enhances their catalytic reactivity to produce hydrogen. The synergistic effect of Ni and Mo on the interaction of d-orbital electrons may decrease the ΔGH on the metal surface so that the reactivity of hydrogen reduction is further increased. Therefore, it is expected that the NiMoZn alloy material should have excellent hydrogen production activity. The plating bath in this study was configured with nickel sulfate, sodium molybdate, zinc chloride, sodium pyrophosphate, and ammonium chloride, with a bias voltage of 4.2 V and a fixed spacing of 35 μm. Micro-electroplating micro-pillars were prepared by adjusting different concentrations of sodium molybdate plating bath. The influence of the composition of the plating bath on the surface morphology, chemical composition, and crystal structure of the alloy microcolumns was discussed. The obtained NiMoZn alloy was observed by SEM for surface morphology, EDS for chemical composition, and XRD for crystal structure. These different NiMoZn alloys were immersed in 1 M KOH solution and measured by cyclic voltammetry and Tafel polarization curve to explore the difference in hydrogen production performance. When the content of sodium molybdate in the plating bath is 0.10 M, the resulting alloy is Ni29.4Mo66.9Zn3.7. It has the smallest Tafel slope (76 mV/dec) and the largest exchange current density value (2.69 mA/cm2). The cyclic voltammetry curve has the largest cathodic current peak (606 mA/cm2) and the smallest hydrogen production onset potential (-0.197 V vs. RHE).