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

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 Pd2+ species on Pd/C catalyst re‐dispersing into uniformly small‐sized Pd0 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 Pd2+ species (Pd(OH)2, PdO) is more active for the dehydrogenation reaction compared to the metallic state Pd0 species. The in‐situ structure evolution induced ultrasmall Pd nanoparticles (2.22 nm) with a constant Pd0/Pd2+ ratio, achieving a high efficiency (98.3%) of H2 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.