Four-Electron Electrocatalytic O₂ Reduction by a Ferrocene-Modified Glutathione Complex of Cu

Abstract

In this manuscript, we design non-precious-metal electrocatalysts for the O2 reduction reaction (ORR) based on Cu complexes of the tripeptide glutathione modified with ferrocene (Cu-GSH-NHFc). Homogenous catalysis experiments demonstrate that the covalently bound Cu-GSH-NHFc catalyst exhibits enhanced activity compared to mixtures of the individual catalyst components. Heterogeneous catalysis results on rotating disk electrodes (RDE) and rotating ring-disk electrodes (RRDE) show that Cu-GSH-NHFc catalyzes the ORR via a four-electron pathway at pH 4–7, while the same catalyst without ferrocene produces significant quantities of H2O2. Cyclic voltammetry reveals electronic coupling between the appended ferrocene moieties and the Cu active site. From these studies, we propose an ORR reaction pathway, in which fast electron transfer facilitated by ferrocene explains the high selectivity of the Cu-GSH-NHFc catalyst. We envision that this understanding will lead to future developments in the design of non-precious-metal ORR catalysts, which are instrumental to fuel cell technologies.

Selective Electrocatalytic Nitrate Reduction to Ammonia Using Nafion-Covered Cu Electrodeposits

“…The electrochemically active surface areas of the electrodes with Cu electrodeposits were measured by conducting CVs in a solution containing Ru­(NH 3 ) 6 Cl 3 (Figure S1), a standard reversible redox couple ( E ° = 0.10 V vs NHE). The more positive potential of ferrocene ( E ° = 0.64 V) compared to Cu ( E ° = 0.34 V) renders ferrocene unsuitable for this experiment because the Cu surface will be oxidized to Cu 2+ at the potentials needed to observe the ferrocene couple . By integrating the charge under the Ru 3+ /Ru 2+ couple for the flat unmodified Cu electrode and comparing that value to the charge measured for the electrodes with Cu electrodeposits, the roughness factors and electrochemically active surface areas of these electrodes were determined.…”

“…The more positive potential of ferrocene (E°= 0.64 V) compared to Cu (E°= 0.34 V) renders ferrocene unsuitable for this experiment because the Cu surface will be oxidized to Cu 2+ at the potentials needed to observe the ferrocene couple. 38 By integrating the charge under the Ru 3+ /Ru 2+ couple for the flat unmodified Cu electrode and comparing that value to the charge measured for the electrodes with Cu electrodeposits, the roughness factors and electrochemically active surface areas of these electrodes were determined. The roughness factors were calculated to be 1.84 and 4.92 for the electrodes with Cu electrodeposits formed at −0.14 and −0.5 V, respectively.…”

Polyaniline/Titania Nanotube-Based Biosensor Strip for Sensitive and Specific Electrochemical Detection of SARS-CoV-2

“…However, it was noticed that a higher redox peak current is observed in the PANi-TNT/SPCE than in the PANi/SPCE. This observation implies the fast electron exchange behavior and electrocatalytic activity 39,40 of the sensing platform due to the higher transfer rate in the presence of TNT. 41,42 To support this study, an electrochemical impedance spectroscopy experiment and analysis were performed, and modified Randles equivalent circuits for both PANi/SPCE and PANi-TNT/SPCE were fitted, which are shown in Figure 2b.…”

Electrocatalytic Oxygen Reduction by Cu Complexes of Tripeptide Derivatives of Glutathione

“…34 Our group recently investigated the ORR activities of Cu complexes of a simple tripeptide, glutathione (GSH). 35 In particular, we synthesized a ferrocene-modified GSH that facilitates fast electron transfer to Cu, which results in higher selectivity for the four-electron reduction of O 2 to H 2 O than the unmodified Cu−GSH complex. These results imply that GSH can serve as an appropriate scaffold for efficient Cu ORR catalysts if properly modified.…”