Nanostructured, Metal-Free Electrodes for the Oxygen Reduction Reaction Containing Nitrogen-Doped Carbon Quantum Dots and a Hydroxide Ion-Conducting Ionomer

Abstract

In this work, we studied the combination of nitrogen-doped carbon quantum dots (N-CQD), a hydroxide-ion conducting ionomer based on polysulfone (PSU) and polyaniline (PANI), to explore the complementary properties of these materials in high-performance nanostructured electrodes for the oxygen reduction reaction (ORR) in alkaline solution. N-CQD were made by hydrothermal synthesis from glucosamine hydrochloride (GAH) or glucosamine hydrochloride and N-Octylamine (GAH-Oct), and PSU were quaternized with trimethylamine (PSU-TMA). The nanocomposite electrodes were prepared on carbon paper by drop-casting. Furthermore, we succeeded in preparing PSU-TMA + PANI + GAH-Oct fibers by electrospinning. The capacitance of the electrodes was investigated by cyclic voltammetry and impedance spectroscopy, which gave similar trends. The ORR was investigated by linear sweep voltammetry at rotating disk electrode speeds between 250 and 2000 rpm in an oxygen-saturated 1 M KOH solution. Koutecky–Levich plots showed that four electrons were exchanged for nanocomposite electrodes containing CQD. The highest reduction currents were measured for the electrodes containing GAH-Oct. The Tafel plots gave the lowest slope and the most positive half-wave potential for PSU-TMA + PANI + GAH-Oct fibers. The best electrocatalytic activity of this electrode could be related to the high amount of graphitic nitrogen in GAH-Oct. Long-term cycling tests showed no significant modification of the onset potential, but a change of the current in the mass transport limited region, indicated the evolution of the microstructure of the nanocomposite ORR electrode modifying the mass transport conditions during the first 400 cycles before reaching stationary conditions. FTIR spectra were used to study possible electrode degradation after the ORR in 1 M KOH: the only change was due to the reaction of PANI emeraldine salt to emeraldine base, whereas the other constituents of the multiphase electrode did not show any degradation.

Electrodeposited Ionomer Protection Layer for Negative Electrodes in Zinc–Air Batteries

“…At the current state of the art, transition metal oxides are developed as the best-performing catalysts; however, inexpensive carbon material support improves the catalyst dispersion and active area and decreases the cost [ 18 ]. Doped carbon materials can also be potent electrocatalysts, especially for the oxygen reduction reaction in alkaline conditions [ 8 , 12 , 19 , 20 , 21 , 22 , 23 ]. Problems arise also concerning the shape and structural changes of the zinc electrode during repeated charge/discharge cycles [ 3 ].…”

Impact of Anion Exchange Ionomers on the Electrocatalytic Performance for the Oxygen Reduction Reaction of B-N Co-doped Carbon Quantum Dots on Activated Carbon

“…We have previously studied heteroatom-doped carbon quantum dots (CQD) as ORR electrocatalyst in alkaline solutions. , The four-electron reduction can be written …”

Influence of Nitrogen Position on the Electrocatalytic Performance of B,N-Codoped Carbon Quantum Dots for the Oxygen Reduction Reaction

“…B,Ndoped CQDs present better ORR catalytic activity in comparison to N-doped CQDs. [27][28][29] Boron is an electron acceptor in carbon, whereas nitrogen is an electron donor. B,N-codoped CQDs have a higher electrocatalytic activity owing to the van der Waals interactions between B and N in CQDs and oxygen.…”