Nitrite reduction over Pd supported CNFs: Metal particle size effect on selectivity

Pd catalysts supported on carbon-nano-fibers (CNFs) were synthesized via Pd colloids stabilized with polyvinyl-alcohol (PVA). Pd catalysts with narrow particle size distributions and mean Pd sizes between 2.6 and 30 nm were immobilized on CNFs. Characterization with CO-chemisorption and transmission electron microscopy (TEM) revealed that a significant part of the Pd surface is blocked by the polymer layer on the Pd particles. The prepared catalysts were tested for nitrite reduction in water, resulting in formation of nitrogen and ammonia. Turn over frequencies were found to be independent of Pd particle size while selectivity to ammonia clearly decreased with increasing Pd particle size.

Particle size effect on activity and selectivity in nitrite hydrogenation; Pd particles partly covered with PVA.Figure optionsDownload high-quality image (144 K)Download as PowerPoint slideHighlights
► The selectivity of nitrite hydrogenation shifts to ammonia with increasing Pd–PVA particle size.
► The activity of Pd particles for nitrite hydrogenation is seriously affected by the presence of PVA.
► The activity per Pd surface atom (TOF) seems independent of particle size.
► The TOF on Pd–PVA appears higher as compared to bare Pd nano-particles.