| 摘要: | 本研究採用本實驗室研發之微陽極影像導引電鍍法(Micro-anode guided electroplating, MAGE)首先製備鎳-鈷合金微柱，用於電催化工作電極產製氫氣。以直徑250 m之白金絲作微陽極，銅線(直徑0.5 mm)作為陰極，兩極間維持80 m之間距，偏壓控制在4.0 V進行電鍍。在陰極上析鍍出純鎳(Ni)及一系列鎳-鈷合金(Ni80Co20 Ni70Co30 Ni61Co39 Ni55Co45 Ni53Co47)微柱。其次，於製備Ni55Co45鍍浴中加入含0.00, 0.10, 0.20, 0.30, 0.40 mM之1T-MoS2奈米粉末，進一步製備鎳-鈷/二硫化鉬複合微電極。所有鎳-鈷合金電極及鎳-鈷/二硫化鉬複合微柱，藉由SEM來觀察表面形貌、EDS分析元素組成以及XRD分析晶體結構，再將這些微柱作為工作電極，浸泡至1.0 M KOH中進行產氫效能之評估，測試方法包括線性掃描伏安法、循環伏安法、計時電位法和電化學阻抗頻譜等四種方法。
結果顯示: 自鎳-鈷合金鍍液中電鍍所得之微柱，隨鍍浴中[Co2+]由0增高至0.10 M時，其SEM表面形貌粗糙度增加，表面出現顆粒狀結構，經EDS分析，當合金中鈷含量超過40 at. %時，表面呈現錐狀物。以[Co2+]/[Ni2+] 濃度比= 0.08 M/1.25 M製備所得之Ni55Co45合金微柱之產氫效能最好；至於所得之Ni-Co/MoS2複合微柱，複合電極之SEM表面形貌則呈現花椰菜狀結節顆粒，顆粒均勻且介面清晰可辨，隨鍍浴中MoS2含量由0 (g/L)上升至0.4 (g/L)，所得複合微柱表面之花椰菜顆粒間隙逐漸縮小。添加0.4 (g/L)之1T-MoS2複合電鍍浴(代號NCM04)析鍍所得之微柱，經EDS分析，其化學組成(at. %) 含有45 % Ni、34%Co、8%Mo、14%S之產氫效能最優。比較產氫效能，Ni-Co合金系列微柱中以Ni55Co45產氫效能最好: 產氫的交換電流密度最大(0.616 mA/cm2)，塔弗斜率最低(106 mV/dec)，在電流密度10 mA/cm2下之瞬時氫過電位最低(有159 mV)，在進行1週次的循環伏安分析中呈現出了最低的起始電位(-0.273 V)以及最大的陰極峰值電流密度(-448 mA/cm2)。
代號NCM04復合微柱產氫的交換電流密度最大(1.843 mA/cm2)，塔弗斜率最低(68 mV/dec)，在電流密度10 mA/cm2下之瞬時氫過電位最低(有89 mV)，在進行1週次的循環伏安分析中呈現出了最低的起始電位(-0.102 V)以及最大的陰極峰值電流密度(-866 mA/cm2)。經調整極化掃描速率來計算電雙層電容(Cdl)，並計算電極的電化學活性表面積(ECSA)，顯示複合電極NCM04具有最大的電化學活性高表面積: 783 cm2具備最高之電化學活性。本論文證實添加二硫化鉬至鎳-鈷合金鍍浴，電鍍所得之Ni-Co/MoS2複合電極，能有效改善鹼性電解水產氫之陰極。
;This study employs the micro-anode guided electroplating (MAGE) method developed in our laboratory to first prepare nickel-cobalt alloy micro-columns for use in electrocatalytic working electrodes for hydrogen production. A platinum wire with a diameter of 250 μm is used as the micro-anode, and a copper wire (diameter 0.5 mm) as the cathode, maintaining a distance of 80 μm between the electrodes, with the plating voltage controlled at 4.0 V. Pure nickel (Ni) and a series of nickel-cobalt alloys (Ni80Co20, Ni70Co30, Ni61Co39, Ni55Co45, Ni53Co47) micro-columns are deposited on the cathode. Next, 1T-MoS2 nanopowder is added to the Ni55Co45 plating bath in concentrations of 0.00, 0.10, 0.20, 0.30, and 0.40 mM to further prepare nickel-cobalt/molybdenum disulfide composite micro-electrodes. All nickel-cobalt alloy electrodes and nickel-cobalt/molybdenum disulfide composite micro-columns are observed using SEM to study surface morphology, analyzed for elemental composition using EDS, and examined for crystal structure using XRD. These micro-columns are then used as working electrodes, immersed in 1.0 M KOH to evaluate hydrogen production performance. The testing methods include linear sweep voltammetry, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy.
Results show that the micro-columns electroplated from the nickel-cobalt alloy bath, with increasing [Co2+] from 0 to 0.10 M, exhibit increased surface roughness and granular structures as observed by SEM. EDS analysis indicates that when the cobalt content in the alloy exceeds 40 at. %, the surface presents conical structures. The Ni55Co45 alloy micro-column prepared with a [Co2+]/[Ni2+] concentration ratio of 0.08 M/1.25 M demonstrates the best hydrogen production performance. As for the Ni-Co/MoS2 composite micro-columns, the SEM surface morphology shows uniform and clearly identifiable cauliflower-like granular nodules. With the increase of MoS2 concentration in the plating bath from 0 to 0.4 mM, the gaps between the cauliflower-like particles on the composite micro-column surface gradually decrease. The micro-columns deposited from a composite electroplating bath with 0.4 g/L 1T-MoS2 (designated as NCM04) exhibit the best hydrogen production performance, with EDS analysis showing a chemical composition (at. %) of 45% Ni, 34% Co, 8% Mo, and 14% S.
Comparing hydrogen production performance, the Ni55Co45 micro-columns in the Ni-Co alloy series exhibit the best performance: highest exchange current density (0.616 mA/cm²), lowest Tafel slope (106 mV/dec), lowest instantaneous hydrogen overpotential at a current density of 10 mA/cm² (159 mV), and the lowest onset potential (-0.273 V) with the highest cathodic peak current density (-448 mA/cm²) during one-week cyclic voltammetry analysis. The composite micro-columns NCM04 show the highest exchange current density (1.843 mA/cm²), lowest Tafel slope (68 mV/dec), lowest instantaneous hydrogen overpotential at a current density of 10 mA/cm² (89 mV), and the lowest onset potential (-0.102 V) with the highest cathodic peak current density (-866 mA/cm²) during one-week cyclic voltammetry analysis. By adjusting the polarization scan rate to calculate the double-layer capacitance (Cdl) and the electrochemical active surface area (ECSA), the composite electrode NCM04 demonstrates the largest electrochemical active surface area of 783 cm², indicating the highest electrochemical activity. |
