Effects of p-substituents on electrochemical COoxidation by Rh porphyrin-based catalysts
摘要:
研究了几种碳支撑的四苯基卟啉铑对 CO 的电化学氧化作用。定量分析显示,介苯基上的 p 取代基对 CO 氧化活性有显著影响。根据光谱和 X 射线结构结果以及电化学分析,对该电催化反应进行了详细表征。本文从对取代基的性质和反应机理的角度讨论了 Rh 罂粟碱之间的活性差异。与现有的铂钌催化剂相比,四(4-羧基苯基)卟啉铑(Rh(TCPP))在测试的卟啉中表现出最高的活性,能在更低的电位下(与可逆氢电极相比,在 60 °C,<0.1 V)高速氧化 CO。这意味着在质子交换膜燃料电池的运行过程中,当施加轻微的过电位时,CO 就会被这种催化剂电化学氧化。与基于铂的催化剂相比,这种催化剂几乎没有 H2 氧化活性。
We have found that certain kind of complexes on carbon black catalyze borohydride electro-oxidation. All of the Rh porphyrins tested in this study exhibited high activity regardless of the structure of the porphyrin ligands. While other metalloporphyrins also catalyzed borohydride electro-oxidation, the activities were much lower than those of Rh porphyrins. Even Rh tetrakis(4-methylphenyl)porphyrin, which exhibited the highest activity, scarcely catalyzed the chemical decomposition of borohydride under open-circuit conditions. These metalloporphyrin-based catalysts tested do not promote H-2 electro-oxidation. Other Rh complexes (Rh2Cl2(CO)(4) and Rh phthalocyanin) also catalyze borohydride electro-oxidation. Rh2Cl2(CO)(4) oxidizes borohydride at lower potentials than Rh porphyrins; it can catalyze borohydride even below 0 V vs. RHE. A one-compartment H-2-generator that also generates electric power was constructed using Rh2Cl2(CO)(4) as an anode catalyst. (C) 2011 Elsevier B.V. All rights reserved.