Mechanically Interlocked Carbon Nanotubes as a Stable Electrocatalytic Platform for Oxygen Reduction

Abstract

Mechanically interlocking redox-active anthraquinone onto single-walled carbon nanotubes (AQ-MINT) gives a new and advanced example of a noncovalent architecture for an electrochemical platform. Electrochemical studies of AQ-MINT as an electrode reveal enhanced electrochemical stability in both aqueous and organic solvents compared to physisorbed AQ-based electrodes. While maintaining the electrochemical properties of the parent anthraquinone molecules, we observe a stable oxygen reduction reaction to hydrogen peroxide (H 2 O 2 ). Using such AQ-MINT electrodes, 7 and 2 μmol of H 2 O 2 are produced over 8 h under basic and neutral conditions, while the control system of SWCNTs produces 2.2 and 0.5 μmol, respectively. These results reveal the potential of this rotaxane-type immobilization approach for heterogenized electrocatalysis.

Immobilized Poly(anthraquinones) for Electrochemical Energy Storage Applications: Structure‐Property Relations

“…In a 0.1 M NaOH solution shown in Figure 6 within the first 3 cycles the faradaic response of PDDA‐SAQ was even higher compared to the PB, but the cycle stability was much worse and there were also some spike‐shaped irregularities observed. These redox‐peak shapes of the immobilized AQ units in the polymeric form are in good agreement with a previous study using a non‐covalent immobilization approach onto carbon nanotubes [32] . Besides a lower j p , PVAQ also showed a quite rapid fading of the faradaic current response in neutral as well as alkaline solution.…”

“…One of the bottle‐necks for broad utilization of AQ‐based energy storage devices is the heavy reductive dissolution of the reduced AQ species in numerous solvents, which limits the long‐term stability [21,26,27] . To overcome this problem, several approaches have been explored throughout the last decades: One non‐reacting approach was mixing of the redox‐active molecules with carbonaceous materials for high integral conductivity as composite [28,29] or by a more specific pathway through the non‐covalently binding of AQ units to carbon nanotubes [30–32] . The second approach was based on immobilizing the redox‐active units in polymeric way, which can be split into two cases.…”

Porous carbon monoliths for electrochemical removal of aqueous herbicides by “one-stop” catalysis of oxygen reduction and H2O2 activation

“…The onset potentials increased monotonically from 0.137 V at pH 1 to 1.008 V at pH 13, which also agrees with the thermodynamics of ORR that a lower proton activity leads to higher Nernstian potential, for both 2-electron (Equation 1) and 4-electron (Equation 2) processes. It's worth noting that a ~0.3 V positive peak shift was achieved by PCM-HDA under similar conditions compared to previous reported mechanically interlocked anthraquinone on SWCNTs (AQ-MINT) electrode (Wielend, 2020). This result confirms the catalytic activity of the PCM-HDA electrode under a mildly reducing potential.…”

Immobilization of molecular catalysts for artificial photosynthesis

“…Wielend et al. demonstrated a new approach of “mechanically interlocking” anthraquinone-based catalysts around CNTs [ 143 ] The rotaxane architecture prevents dissolution problems of physically adsorbed organic molecules upon electrochemical reduction, while retains the electrochemical properties of the pristine molecule (Fig. 9 ).…”

“…9 Electrocatalytic O 2 reduction with a mechanically interlocked CNT with an anthraquinone macrocycle. Copyright permission from ACS [ 143 ] …”