Ultrafine palladium nanoparticles deposited on Ni, N co-doped carbon to boost dehydrogenation efficiency of perhydro-N-phenylcarbazole

Liquid organic hydrogen carriers (LOHCs) are considered as promising candidates for large-scale hydrogen storage, which offers significant advantages in terms of hydrogen storage density, ease of storage and transportation. NPhCZ (N-phenylcarbazole)/18H-NPhCZ (perhydro-N-phenylcarbazole) is proposed as a typical system with high hydrogen storage capacity. However, low dehydrogenation activity and selectivity of catalysts restrict the cyclic efficiency of hydrogen storage. In this study, the efficient catalysts are designed by the immobilization of ultrafine, highly dispersed Pd nanoparticles onto Ni, N co-doped carbon materials through wet chemical reduction. The Pd/Ni@NC-10 catalyst exhibits the highest catalytic performance with 100 % conversion, 81.9 % selectivity of NPhCZ and 6.48 wt% hydrogen release amount. Combined with XRD, HRTEM, Raman, XPS, H2-TPR, 2-TPR, N2 2 physisorption characterization methods and DFT calculations, it is found that the doped Ni, N species could synergistically increase the dispersion of loaded Pd nanoparticles, as well as regulate the electronic state around Pd, which in turn accelerates the rate of the rate-limiting step. The evident interaction between Pd nanoparticles and Ni, N co-doped carbon brings the enhancement of dehydrogenation efficiency. Besides, the spent catalysts are measured by XRD, TEM, XPS and evaluated for the dehydrogenation reaction, indicating that Pd/Ni@NC-10 shows good structural stability, durability and recyclability. It provides practical guidance for the design of LOHCs dehydrogenation catalysts.