Diversity of Pd-Cu active sites supported on pristine carbon nanotubes in terms of water denitration structure sensitivity

• Published in: Applied catalysis. A, General Vol. 559; pp. 187 - 194
• Main Authors: Panic, Sanja, Srdić, Vladimir, Varga, Tamás, Kónya, Zoltán, Kukovecz, Ákos, Boskovic, Goran
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 05-06-2018; Elsevier Science SA
• Subjects: Ammonia; Bimetallic particle composition; Bimetals; Carbon nanotubes; Catalysis; Catalysts; CNT lattice defects; Copper; Crystal defects; Crystal lattices; Denitration; Nanoparticles; Nanotubes; Organic chemistry; Particle size; Pd Particle size; Pd-Cu/CNTs catalysts; Sensitivity analysis; Structure sensitivity effect; Water denitration; Structure sensitivity effect; Pd Particle size; CNT lattice defects; Water denitration; Pd-Cu/CNTs catalysts; Bimetallic particle composition
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2018.04.032

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•Catalytically formed CNT defects are Pd-Cu anchoring sites for catalyst preparation.•Formation of CNT defects by functionalization using strong acids can be avoided.•The extent of CNT lattice defects govern metal active sites size and composition.•Presence of ordered Pd-Cu alloy is beneficial for high nitrate conversion.•Highest N2 selectivity in unordered alloy is due to specific Cu atoms positioning.
Four Pd-Cu-based (2:1 wt.%) catalysts for water denitration, differing in physico-chemical characteristics and structural quality, were prepared, using carbon nanotubes (CNTs) as supports. The extent of lattice defects in the pristine CNTs turned out to govern resulting varieties of Pd nanoparticle size and the composition of the bimetallic (Pd:Cu) entities in the catalysts, playing an important role in nitrate reduction. Catalyst samples characterized by close proximity of Pd and Cu, as in an alloy, displayed the highest degree of nitrate conversion. At the same time, the size of the Pd particles, alone, or decorated to different extents with Cu atoms, was found to be critical for the second step of denitration reaction, directing the formed nitrite to either N2 or NH3. Water denitration is a structure sensitive reaction related to Pd particle size, and this effect is further emphasized in the decoration of the particle by the incorporation of Cu atoms into Pd particle corners and edges.