Impact of Anions on Electrocatalytic Activity in Palladium Nanoparticles Supported on Ionic Liquid–Carbon Nanotube Hybrids for the Oxygen Reduction Reaction

Abstract

A series of palladium nanoparticles supported on carbon nanotubes (CNTs), which were functionalized covalently with imidazolium polymer salts with different anions, Pd/polyIL(X)-CNTs (IL=ionic liquid; X=Cl, Br, I, ClO(4), BF(4), PF(6)), were prepared to investigate the influence of imidazolim salt anions on electrocatalytic activity in the oxygen reduction reaction (ORR). The anions of the imidazolium moiety significantly impacted on the ORR kinetics in a 0.1 M solution of HClO(4). The electronically active surface area results are in good agreement with the order of the ORR kinetic activity of the supported Pd/polyIL(X)-CNTs (X: Cl>ClO(4)>BF(4)>Br≈PF(6)≫I). In contrast, owing to the facile anion exchange of halide anions with hydroxide anions, anion-dependent catalytic activity has not been observed in 0.1 M NaOH. Iterative ORR experiments in acid-base solutions demonstrated anion exchange on the electrode. These results indicate that subtly varied structures of the IL moiety profoundly influence the performance of IL-CNT hybrid materials and molecular-level control of interfacial interactions between the support material, catalysts, and electrolytes is important in the design of supported metal nanoparticle catalysts for fuel cells.

Insight into the immobilization of ionic liquids on porous carbons

“…This allows, thus, a broad variety of arrangements and interactions of the IL within the support surface. There are some works dealing with SILP systems based on carbon materials using for example a carbon cloth [17,18], carbon nanofibres that cover sintered metal fibres [19], commercially available mesoporous and microporous carbon beads [20], commercial activated carbons [21] and carbon nanotubes [22][23][24][25].…”

Covalently Supported Ionic Liquid Phases: An Advanced Class of Recyclable Catalytic Systems

“…For example, CNTswere covalently functionalized with imidazolium polymers alts with different anions, Pd/polyIL(X)-CNTs 84 (X = Cl, Br,I ,C lO 4 ,B F 4 ,P F 6 )t om aximize the anion content (Scheme 36). [75] These materials were prepared with the aim of investigating the influence of imidazolium salt anions on electrocatalytic activity in the oxygen reduction reaction. The synthesis was accomplished by radical polymerizationo ft he N-allylimidazolium halide functionalized CNTs 83 with N-vinyl-N-butylimidazolium halide to provide the corresponding polyIL(X)-CNTs( X = Cl, Br,I ).…”

Measurement of the Quantum Conductance of Germanium by an Electrochemical Scanning Tunneling Microscope Break Junction Based on a Jump‐To‐Contact Mechanism

“…· germanium · ionic liquids · nanowires · scanning probe microscopy ionic liquids, including a wide electrochemical window, low vapor pressure, and moderate solubility, [12][13][14][15][16][17][18] the STM-BJ technique based on a jump-to-contact mechanism could provide a good opportunity to investigate the quantum conductance of germanium, which could not be achieved in aqueous solution owing to the limitation of the electrochemical window. Most importantly, the technique can ensure homogeneous breakages during conductance measurements.…”