Structure Evolution of Pd/C Catalyst in the Catalytic Dehydrogenation of Dodecahydro‐<i>N</i>‐ethylcarbazole: Effects of Pd Species and Particle Size

Abstract The dehydrogenation of liquid organic hydrogen carriers is of significant potential for hydrogen energy applications. We successfully synthesized a highly efficient and stable Pd/C catalyst featuring ultrasmall (2.22 nm) and stable Pd nanoparticles via the deposition–precipitation method for the dehydrogenation of dodecahydro‐ N ‐ethylcarbazole. Interestingly, the Pd structure evolves during the reaction, with the Pd 2+ species on Pd/C catalyst re‐dispersing into uniformly small‐sized Pd 0 nanoparticle under reaction conditions. The conventional thermal treatment of calcination–reduction typically results in larger Pd particles due to the stronger metal‐support interaction. Kinetic studies revealed the oxidation state of Pd 2+ species (Pd(OH) 2 , PdO) is more active for the dehydrogenation reaction compared to the metallic state Pd 0 species. The in situ structure evolution induced ultrasmall Pd nanoparticles (2.22 nm) with a constant Pd 0 /Pd 2+ ratio, achieving a high efficiency (98.3%) of H 2 release from 12H‐NECZ dehydrogenation at 180 °C. This work provides a simple method for preparing highly dispersed Pd/C catalyst with stable ultrasmall Pd particles, offering valuable insights to researchers in the field of supported metal catalysts.