The development of organic-based metal-free catalysts is vital for the commercialization of fuel cells. At present, novel indole derivatives (2-((5-(5-[1-Methyl-2-phenyl-1H-indol-3-yl] thiophen-2-yl)furan-2-yl) methylene) malononitrile ITFM and 2-((5′-(1-Methyl-2-phenyl-1H-indol-3-yl)-(2,2′-bithiophen)-5-yl)methylene) malononitrile ITTM were designed, synthesized, and their electrochemical properties were investigated. First, one-pot two-step cyclization reactions were applied for the synthesis of intermediate 1-methyl-2-phenyl-3-(thiophen-2-yl)-1H-indole (5). Then, halogenation reaction and Suzuki-Miyaura coupling reactions were used for the formation of intermediate 5-(5-[1-methyl-2-phenyl-1H-indol-3-yl] thiophen-2-yl) furan-2-carbaldehyde (8) and 5′-(1-methyl-2-phenyl-1H-indol-3-yl)-[2,2′-bithiophene]-5-carbaldehyde (12). Finally, ITFM and ITTM were isolated in 76% and 60% yields via condensation reactions. Then, glucose electrooxidation performance of these indole derivatives were examined by using Cyclic Voltammetry (CV), Chronoamperometry (CA), and Electrochemical Impedance Spectroscopy (EIS) in 0.5 M glucose alkaline solution. ITTM exhibited the best glucose electrooxidation activity because the specific activity of ITFM was found as 0.46 mA/cm², and ITTM gave the 0.52 mA/cm². CA results revealed that the specific activity and stability of ITTM were greater than ITFM catalysts. EIS results were also in agreement with CV and CA results that the charge transfer resistance (R_ct) of ITFM was greater than ITTM displaying that ITTM improved charge-transfer kinetics. As a result, an indole derivative-based catalyst is a new generation of environmentally friendly and alternative catalyst for direct glucose fuel cells.

中文翻译：

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用于葡萄糖电氧化的吲哚基新型有机阳极催化剂

有机基无金属催化剂的开发对于燃料电池的商业化至关重要。目前，新型吲哚衍生物（2-（（5-（5-[1-甲基-2-苯基-1H-吲哚-3-基]噻吩-2-基）呋喃-2-基）亚甲基）丙二腈ITFM和设计、合成了2-((5'-(1-Methyl-2-phenyl-1 H -indol-3-yl)-(2,2'-bithiophen)-5-yl)methylene) 丙二腈ITTM电化学性能研究，首先应用一锅两步环化反应合成中间体1-甲基-2-苯基-3-(噻吩-2-基)-1H-吲哚( 5). 然后，卤化反应和 Suzuki-Miyaura 偶联反应用于形成中间体 5-(5-[1-methyl-2-phenyl-1H-indol-3-yl] thiophen-2-yl) furan-2-carbaldehyde (8)和 5'-(1-甲基-2-苯基-1H-吲哚-3-基)-[2,2'-联噻吩]-5-甲醛(12)。最后，通过缩合反应以 76% 和 60% 的收率分离ITFM和ITTM 。然后，通过使用循环伏安法 (CV)、计时电流法 (CA) 和电化学阻抗谱 (EIS) 在 0.5 M 葡萄糖碱性溶液中检测这些吲哚衍生物的葡萄糖电氧化性能。ITTM表现出最好的葡萄糖电氧化活性，因为ITFM的比活性发现为 0.46 mA/cm ²，而ITTM给出了 0.52 mA/cm ²。CA 结果表明，ITTM 的比活性和稳定性高于ITFM催化剂。EIS 结果也与 CV 和 CA 结果一致，即 ITFM 的电荷转移电阻 ( R ct ) 大于 ITTM ，_表明ITTM改善了电荷转移动力学。因此，基于吲哚衍生物的催化剂是直接葡萄糖燃料电池的新一代环保替代催化剂。