為因應全球能源轉型，再生能源的需求與日俱增，氫能源因其高能量密度和零污染而受到關注。其中水電解是生產氫氣最「綠色」的方法之一，其由陰極的析氫和陽極的析氧組成，過程中不涉及碳的產出。然而這兩種電化學過程都面臨著反應動力學緩慢的狀況，商用及過去所研究的水電解系統額外的高過電位以及催化材料昂貴的價格使得水電解產氫的成本居高不下。已有許多研究試圖開發低成本的過渡金屬催化劑來取代商用的貴金屬催化劑，其中以鎳基材料的性能最為理想，尤其是異質的鎳基催化結構。在本研究中，我們提供了一種於含水氯化膽鹼/尿素深共熔溶劑 (Deep Eutectic Solvent, DES)中進行的一步驟電沉積程序，利用該系統來製備奈米結構的氫氧化鎳/鎳/碳纖維氈複合電極，以催化整體水分解析氫。 實驗使用含有不同水量(1.86 wt.%、11.69 wt.%以及21.67 wt.%)的氯化膽鹼/尿素DES作為電沉積溶液，並改變施加的電壓做為電沉積的參數。我們發現在含水DES的體系中可以合成鎳/氫氧化鎳異質催化結構，-1.5CU10W複合電極表面超薄的氫氧化鎳奈米片為析氫及析氧反應提供豐富的活性位點，並且氫氧化鎳和鎳之間的協同作用以及活性Ni3+物質的存在為析氫及析氧提供了有利的條件。該電極在鹼性溶液中表現出超低的析氫過電位(30 mV@10 mA/cm2)，優於大多數報導的值。較小的塔佛斜率和電荷轉移阻抗表明-1.5CU10W複合電極具有良好的催化動力學和快速的電子傳輸能力。此外，由穩定性測試所得的電解槽析氫電壓為1.69 V，表明-1.5CU10W複合電極具有實際用作雙功能催化劑的潛力。根據複合電極所表現的優異催化性能，我們認為含水DES系統的電沉積是一種製備高活性催化劑的有效方法。 ;In response to the global energy transition, the demand for renewable energy has increased recently, and hydrogen energy has attracted attention owing the high energy density and zero greenhouse gas emission. Water electrolysis is one of the most ′′green′′ tactics to produce highly pure hydrogen. In general, water splitting is consisted of anodic oxygen evolution (OER) and cathodic hydrogen evolution reaction (HER). However, these two electrochemical processes are faced with sluggish reaction kinetics, leading to a higher electrolysis voltage, increased energy consumption and hydrogen price. Many studies have attempted to develop low-cost transition metal catalysts to replace commercial noble metal catalysts, among which the performance of nickel-based materials is the most ideal, especially the heterostructure nickel-based catalyst. In this work, we provide a one-step electrodeposition process in water-containing choline chloride/urea deep eutectic solvent (ChCl/urea DES) to prepare nanostructured nickel hydroxide/nickel/carbon fiber felt composite electrodes for water splitting. According to the materials characterizations, we found that the Ni(OH)2/Ni heterostructure can be successfully synthesized by the water-containing DES system. The -1.5CU10W electrode with ultrathin nickel hydroxide nanosheets on the surface possesses an enriched active site. Also, the possible synergistic effects between Ni(OH)2 and Ni as well as the presence of active Ni3+ species lead to the enhanced HER and OER performance. It is worth noting that -1.5CU10W electrode exhibits an ultra-low HER overpotential (30 mV@10 mA/cm2) in alkaline solution, which is better than most reported values. The smaller Tafel slope and charge transfer impedance indicate that -1.5CU10W electrode has good catalytic kinetic and fast electron transportability. Furthermore, The overall cell voltage obtained by the stability test was 1.69 V, indicating that -1.5CU10W electrode has the potential to replace commercial catalysts. The excellent catalytic performance of the composite electrode suggests that the electrodeposition in a water-containing DES system is an efficient strategy to prepare highly active catalysts.
