Controlled electron transfer at the Ni-ZnO interface for ultra-fast and stable hydrogenation of N-propylcarbazole

Developing cost-effective and efficient hydrogenation catalysts is crucial for Liquid Organic Hydrogen Carrier (LOHC) technology. ZnO-modified Ni/Al2O3 catalysts were prepared and evaluated for their catalytic hydrogenation of N-propylcarbazole (NPCZ). Among all catalysts, NiZn11Al achieved saturation hydrogenation of NPCZ within 25 min and exhibited excellent potential for industrial applications. The moderate amount of ZnO enhanced the dispersion of Ni nanoparticles, while excessive ZnO inhibited dispersion and promoted Ni-Zn alloy formation. The amount of ZnO doping determined the interaction strength and direction of electron transfer between Ni and ZnO. The formation of the Ni-ZnO interface effectively prevented agglomeration of Ni nanoparticles and improved catalytic stability for NPCZ hydrogenation. Dispersed Niδ+ boosted hydrogen activation, and the strong acid sites of the catalyst promoted the hydrogenation activity. The synergistic effect of Ni and ZnO was shown to accelerate the hydrogenation rate and lower the activation energy compared with Ru-based catalysts. [Display omitted] •NiZn11Al catalyst achieved fully hydrogenation of NPCZ within 25 min without significant deactivation after 10 cycles.•Moderate amount of ZnO enhanced the dispersion of Ni nanoparticles, excessive amount inhibited it.•Electron transfer from Ni to ZnO forms large amounts of Niδ+ and is essential for hydrogen activation.•Synergistic effect of Ni and ZnO is crucial for accelerating the hydrogenation rate and lowering the activation energy.•Controlled electron transfer at the Ni-ZnO interface plays a crucial role in enhancing catalytic activity and stability.