Preparation of Ni@Pd Core–Shell Nanoparticles Supported on KIT-6 by Ultrasound-Assisted Galvanic Replacement for Dodecahydro-N-ethylcarbazole Dehydrogenation

Abstract

Using Ni as a template and reductant, Ni core−Pd shell nanoparticles (Ni@Pd NPs) supported on KIT-6 (Ni@Pd/ K6) were prepared by a galvanic replacement reaction under ultrasonic radiation. The characterization results show that the Ni@Pd core−shell NPs with an average diameter of 1.9 ± 0.3 nm are uniformly dispersed on KIT-6. The d-band center position of Pd in Ni@Pd core−shell NPs can be affected by both ligand and strain effects. The relationship between the d-band center of Pd and the selectivity of intermediates is a nearly straight curve. The dehydrogenation efficiency of dodecahydro-N-ethylcarbazole on Ni@Pd(6:1)/K6 is 100% only for 3 h at 180 °C and 95.5% for 6 h at 160 °C, which is better than the reported catalysts. The outstanding catalytic dehydrogenation performance of Ni@Pd(6:1)/K6 can be attributed to the synergistic effect of the ligand and strain effect, the high dispersion of core−shell NPs, and the weak H 2 binding ability of the catalyst.

V-Promoted Ultrasmall Pd Nanoparticles Supported on V-KIT-6 for the Enhanced Catalytic Dehydrogenation of Perhydro-N-ethylcarbazole

“…The lower peak area in the α region usually correlates with that of the Pd δ+ species, which has weakly chemisorbed hydrogen atoms and is more likely to desorb. In contrast to the previous study by Bai et al, two hydrogen spillover peaks appeared in the β region of Pd/KIT-6. It is known that a pure KIT-6 support does not exhibit the “hydrogen spillover” phenomenon.…”

“…Additionally, the size effect has been shown to play an important role in dehydrogenating LOHCs. , High specific surface area together with unique pore structure may also benefit the active compositions. Bai et al investigated Pd nanoparticles size effect induced by different supports, and found that a support with a 3D network of pore channels can significantly decrease Pd loading and enhance dispersion. − Although many efforts have been made to improve these deficiencies and enhance the catalytic efficiency of noble metals, stabilizing the metal particle size for long-term catalytic activity and accelerating the reaction rate of 4H-intermediate conversion to 0H product remain key challenges for realizing large-scale applications of LOHCs.…”

“…The catalyst is prone to deactivation due to carbon coking over time during the reaction process. , Therefore, modulating the VO x species on the support surface to reduce carbon coking is crucial to enhancing the catalytic performance. Mesoporous silica support, such as KIT-6 with a high specific surface area, may be a more appropriate choice for Pd catalytic dehydrogenation. − , In addition, to date there is no report on a trace transition metal decorated effect in the catalytic hydrogenation/dehydrogeantion reactions of LOHCs.…”