Boosting dehydrogenation of dodecahydro-N-ethylcarbazole over Pd nanoclusters with tailored electronic structures loaded on nitrogen-doped carbon

Dodecahydro-N-ethylcarbazole (12H-NEC) is considered as a highly promising liquid organic hydrogen carrier, but its commercial application is constrained by the requirement of large amounts of precious metal catalysts for dehydrogenation. Herein, Pd nanoclusters with an average particle size of 1.1 nm supported on amine groups modified carbon blacks (Pd/N–CHNO3) are developed to efficiently catalyze the dehydrogenation of 12H-NEC with a low loading of Pd (2.2 wt%, 0.12 mol%). Induced by the nitrogen doping in the carbon black, the d-band center of the Pd (111) surface shifts from −1.64 eV to −1.53 eV, resulting in the electron-deficient structure of thus-formed Pd nanoclusters owing to the electron transfer from Pd to N atoms and uniform distribution of Pd nanoclusters inside of carbon blacks. This electron transfer effectively tunes Pd0:Pdδ+ ratio for enhancing the adsorption of reactant species of 12H-NEC on the surface of Pd nanoclusters and hence facilitates the catalytic role of Pd nanoclusters in enhancing the hydrogen desorption performance of 12H-NEC. As a result, every step of the dehydrogenation of 12H-NEC under the catalysis of Pd nanoclusters on the nitrogen-doped support exhibits lower ΔG values compared to the non-doped support, which provides direct evidence to the important role of the nitrogen doping of the catalyst support in improving the dehydrogenation performance of 12H-NEC on the Pd surface. Therefore, a hydrogen release capacity of 5.60 wt% with 100% conversion and a selectivity of 90% could be obtained for 12H-NEC under the catalysis of Pd nanoclusters supported on amine-functionalized carbon black at 453 K with a low precious metal dosage (0.12 mol%).