| 摘要: | 電催化二氧化碳還原反應(electrochemical CO₂ Reduction Reaction, eCO2RR)，為將空氣中的二氧化碳透過一系列的電化學反應，將其還原成具有經濟價值的產物，如甲酸(HCOOH)、乙醇(C2H5OH)等等，由於其具有易於應用在工業應用以及可持續能源轉化的巨大潛力，因此在實現碳中和目標上備受關注。本研究藉由微陽極影像導引電鍍法(Micro-Anode Guided Electroplating, MAGE)製備銅-錫二元合金微柱，進而以此微柱作為電催化還原之工作電極，在0.1 M KHCO3中通入二氧化碳(CO2)，探討其eCO2RR催化之活性，以及在不同電位下之還原產物。MAGE製程中以直徑500 μm之鉑絲底面積圓盤做為微陽極，8.5*105 μm2表面積之銅片為陰極。兩電極維持160μm之間距在4.0 V偏壓下電鍍。鍍液中含硫酸銅、硫酸亞錫為主鹽，抗壞血酸為還原劑及檸檬酸鈉為螯合劑，在室溫下鍍浴中製備銅-錫合金微柱。析鍍所得的合金微柱藉由掃描式電子顯微鏡(SEM)分析表面形貌，以能量散佈光譜(EDX)分析元素組成、X光結晶繞射(XRD)分析結晶結構以及X光光電子能譜儀分析表面元素。結果顯示:當鍍浴中硫酸銅濃度設定在0.01 M、0.02 M、0.04 M、0.12 M下，所得微柱具有三維結構，其中銅含量依序增高，以代號區別為CS 01 (Cu30Sn70)、CS 02 (Cu50Sn50)、CS 04 (Cu70Sn30)、CS 12 (Cu20Sn80)。微柱之二氧化碳還原電催化反應，以三極式標準電化學槽，在0.1 M KHCO3下，利用線性掃描伏安法(LSV)、環伏安法(CV)，計時電流法(CA)等直流電測試；阻抗頻譜(EIS)交流量測法，由LSV所得塔弗斜率，CV所得電化學活性表面積(ECSA)等結果探討樣品之電催化性能。另一方面，以化學分析法定性、定量測定在不同電位下，二氧化碳電化學還原所得之產物。所使用儀器包含核磁共振頻譜(NMR)、氣相層析儀(GC)、傅立葉轉換紅外光譜(FTIR)等。電化學檢測結果顯示: 在MAGE析鍍所得所有4種銅-錫微柱中，以CS 02 (Cu50Sn50) 微柱在電催化二氧化碳還原生成甲酸時，其效能最高，具最低之塔弗斜率(154.7 mV/dec-1)與最大的ECSA(230.69 cm2)，尤其在-0.9 V時生成甲酸(HCOOH)有最高的法拉第效率(93.46 %)。;The electrochemical CO₂ reduction reaction (eCO₂RR) involves the reduction of carbon dioxide (CO₂) from the atmosphere into economically valuable products, such as formic acid (HCOOH) and ethanol (C₂H₅OH), through a series of electrochemical reactions. Its significant potential for scalability in industrial applications and sustainable energy conversion has made it a key focus in achieving carbon neutrality.
In this study, copper-tin binary alloy microcolumns were fabricated using the Micro-Anode Guided Electroplating (MAGE) method and used as working electrodes for electrocatalysis. The catalytic activity of these microcolumns for eCO₂RR was investigated in 0.1 M KHCO₃ under CO₂ atmosphere, along with the products formed at different potentials. During the MAGE process, a platinum disk (made of Pt-wire with a diameter of 250 μm) was used as the micro-anode, and a copper plate ( in an area of 8.5*105 μm2) was the cathode. The micro-anode and cathode were maintained at a distance of 160 μm, under a bias of 4.0 V during electrodeposition. The MAGE was performed in a bath consisted of copper sulfate and stannous sulfate as primary salts, ascorbic acid as a reducing agent, and sodium citrate as a complexing agent at room temperature. The Cu-Sn microcolumns prepared were denoted as CS 01, CS 02, CS 04 and CS 12 from the bath in which the concentration of copper sulfate in the bath varied in 0.01 M, 0.02 M, 0.04 M, and 0.12 M. The microcolumns were characterized through scanning electron microscopy (SEM) for surface morphology, energy dispersive X-ray spectroscopy (EDX) for elemental composition, and X-ray diffraction (XRD) for crystal structure analysis. It was found that microcolumns exhibited three-dimensional structures. The chemical composition (in at. wt%) of the microcolumns reveals the order CS 01 (Cu30Sn70), CS 02 (Cu50Sn50), CS 04 (Cu70Sn30) and CS 12 (Cu20Sn80).
The electrocatalytic reaction of carbon dioxide reduction on the microcolumn was carried out in a three-electrode standard electrochemical cell in 0.1 M KHCO3 through direct-current methods such as linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry (CA); and alternating-current technique by means of electrochemical impedance spectroscopy (EIS). The data of Tafel slope obtained from LSV and thoe of the electrochemically active surface area (ECSA) from CV were used for evaluation. On the other hand, qualitative and quantitative analyses of the products come from the electrochemical reduction of carbon dioxide at different potentials were through instruments like nuclear magnetic resonance spectroscopy (NMR), gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), etc. The electrochemical characterization demonstrated that among four Cu-Sn microcolumns resulted from MAGE plating, CS 02 (Cu50Sn50) displays the highest efficiency in electrocatalytic reduction of carbon dioxide into formic acid, due to the lowest Tafel slope (154.7 mV/dec-1) but the largest ECSA (230.69 cm2). Especially at -0.9 V, it has the highest Faradaic efficiency (93.46 %) to produce the formic acid (HCOOH). |
