The synergistic effect of the carbon shell pore volume and core Pd size of Pd@hollow@C-X for the synthesis of H2O2

Abstract

Yolk–shell Pd@hollow@C-X (X = 1.5, 3.2, 4.5 and 6) catalysts with Pd as the core and porous carbon as the shell were prepared via the inverse microemulsion method. The carbon shell pore volume and core Pd size were controlled by varying the NH₃·H₂O amount. Results showed that with an increase in the NH₃·H₂O amount, the average particle size of Pd nanoparticles and shell pore volume decreased first and then increased, and when the NH₃·H₂O amount was 3.2 ml, the as-prepared Pd@hollow@C-3.2 catalyst had the smallest Pd particle size and largest shell pore volume as 5.54 ± 1.37 nm and 0.12 m³ g⁻¹, respectively. The smaller Pd particle size can provide more active sites for the adsorption and reaction of H₂ and O₂ reactants, and the larger shell pore volume is beneficial for their adsorption. This makes the Pd@hollow@C-3.2 catalyst possess the highest selectivity and productivity in the H₂O₂ synthesis, reaching 93% and 3197 mmol (g_Pd⁻¹ h⁻¹)⁻¹, respectively, at 1 bar.