Synergistic effect of Pd-Co₃O₄ nanoparticles supported on coffee-derived sulfur, nitrogen-codoped hierarchical porous carbon for efficient methanolysis of NaBH₄

Sulfur, nitrogen-codoped (SN-doped) highly porous carbon nanostructures (CNSs) are established as efficient components for hydrogen generation applications. Waste coffee grounds are carbonized in situ and activated with KOH to produce hierarchically SN doped porous carbon nanostructures with a large specific surface area of 2320 m² g⁻¹. The amorphous and highly active Pd-Co₃O₄ nanoparticles (NPs) are anchored onto an SN-codoped carbon nanosheet prepared via a simple hydrothermal reaction. An effective method for optimization of the Pd-Co₃O₄/SN-CNS-600 catalytic efficiency for NaBH₄ methanolysis using sodium sulfide as a precursor or combination of sulfur-containing salts as a raw material is proposed. The Pd-Co₃O₄/SN-CNS-600 catalyst exhibits an excellent catalytic activity for NaBH₄ catalytic methanolysis at room temperature, with a high hydrogen generation rate of 20158 mL H₂ min⁻¹ g_cat⁻¹. The methanolysis reaction activation energy in an aqueous NaBH₄ solution is approximately 14.52 kJ/mol. The excellent Pd-Co₃O₄/SN-CNS-600 catalytic activity is attributed to the small size and amorphous state of Pd-Co₃O₄ NPs, good synergistic interaction between Pd-Co₃O₄ NPs and SN-CNS with a large specific surface area, and abundant defects. Highly efficient, inexpensive, and environment-friendly catalysts are successfully developed for hydrogen generation.