Unusual Pd nanoparticle dispersion in microenvironment for p-nitrophenol and methylene blue catalytic reduction

Palladium based catalysts are highly attractive for catalytic reactions. However, the catalytic activity is dependent on the dispersion and size of Pd nanoparticles (NPs). Herein, an efficient strategy is developed to regulate the size and dispersion of Pd NPs in nanoconfined spaces provided by Santa Barbara Amorphous-15 (SBA-15) occluded with template. The Pd precursor is introduced to the confined spaces between the template and silica walls in as-synthesized SBA-15 (AS) by grinding. Subsequent reduction allow template removal and precursor conversion to Pd⁰ in single step and avoids aggregation that take place in calcined SBA-15 (CS). Our results show that up to 1.0 wt% of Pd can be well dispersed in confined spaces of AS (denoted as 1.0PdAS), while sever aggregation take place from CS with the same Pd loading (denoted as1.0PdCS). We also demonstrated that 1.0PdAS is highly efficient for catalytic reduction of p-nitrophenol (P-NP) and Methylene blue (MB) with rate constant of 0.4924 and 0.626 min^-1, respectively, which is superior than 1.0PdCS attributed to well dispersed and smaller size (3 nm) Pd NPs. Furthermore, no change in the rate constant of P-NP (0.4924 min^-1) and MB (0.626 min^-1) after regeneration presents good stability of 1.0PdAS in catalytic reactions.