Enhancing the Dehydrogenation Efficiency of Heterocyclic Aromatic Hydrocarbon By Pd and Pt-Based Catalysts

In recent decades, hydrogen energy has played an important role on the sustainable development of the word. It is necessary to provide an appropriate technology for hydrogen storage to promote its commercial applications. Previous reports indicated that liquid organic hydrogen carriers (LOHC) exhibited significant advantages in stationary hydrogen storage system. The N-ethylcarbazole (NECZ) and dodecahydro-N-ethylcarbazole (12H-NECZ) system has been regarded as an ideal candidate of LOHC. However, the low selectivity of dehydrogenation reaction and high cost of commercial catalysts restrict the industrial applications. In this work, SiO₂, TiO₂ and Al₂O₃ are selected to synthesize Pd and Pt-based catalysts. For the Pd-based catalysts, we find that the dehydrogenation activity and selectivity are enhanced significantly by doping Cu, Ni and Co due to the bimetallic synergistic effect. Pt/TiO₂and Pt/Al₂O₃ exhibit higher catalytic activity and selectivity than the Pd-based catalysts with similar metal load. The calculated TOFs are partially dependent on the particle size and dispersity of catalysts, suggesting that the dehydrogenation process is structure sensitive. After optimization for the Pt/TiO₂ catalysts, 1.0 wt% Pt/TiO₂ shows the 99.3% dehydrogenation capacity at 453 K, evidently higher than those of commercial Pd and Pt-based catalysts. Combined with the analysis of XRD, XPS, TEM, TPR, it is found that the enhancement of 12H-NECZ dehydrogenation efficiency is attributed to the promotion on the activation of the intermediates due to the strong metal-support interaction (SMSI) and surface structure of catalysts. This research can help reveal the hydrogen storage mechanism and provide guidance for designing new catalysts.