Ultralow Rh Bimetallic Catalysts with High Catalytic Activity for the Hydrogenation of N-Ethylcarbazole

Liquid organic hydrogen carrier (LOHC) has attracted a great deal of attention in recent years for its use in hydrogen storage. Supported Rh catalyst has been widely used in the hydrogenation reaction of the N-ethylcarbazole (NEC), one of the most promising LOHCs. However, the high Rh content is challenging because of its high cost. Herein, we successfully developed a γ-Al2O3-supported Rh-Ni bimetallic catalyst with only 0.1 wt % Rh, which showed excellent catalytic performance in the hydrogenation of NEC with a high conversion of 99% and high selectivity of 98% in 2 h. Various characterizations such as high-angle annual dark-field scanning transmission electron microscopy images with phase mappings, X-ray photoelectron spectroscopy, H2 temperature-programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy confirmed that the excellent catalytic performance was ascribed to the following factors: (i) electron transfer between the bimetallic Rh-Ni nanoparticles (NPs) structure on the catalyst support; (ii) formation of smaller Ni NPs on the bimetallic Rh-Ni catalyst, which was promoted by Rh; (iii) increased reducibility of the loaded NiO during the catalyst preparation process as a result of the highly dispersed single Rh atom. Thus, the prepared catalyst with ultralow Rh content in this work still has outstanding catalytic activity and sheds light on a fruitful strategy for developing low-cost hydrogenation catalysts of NEC for hydrogen storage.