Abstract
The state-of-the-art procedure for investigating homogenous and heterogeneous electrocatalysts is cyclic voltammetry (CV). However, this technique usually requires an inactive electrode material. One common problem arising e. g. in studying the oxygen reduction reaction (ORR) is the significant background contribution to the overall ORR current provided by many carbon-based and metal-based electrode materials. Furthermore, rotating ring-disc electrodes (RRDEs) made of common materials like glassy carbon/platinum (GC/Pt) can be affected by overlapping reduction potentials on the disc. Interference from overlapping reactions on the ring might also occur, particularly in connection with oxygen reduction and hydrogen peroxide oxidation in ORR studies.We present herein a novel subtraction method which allows a semi-quantitative description of homogeneous electrocatalysts and helps to overcome the overlapping problems described above using anthraquinone-2-sulfonate (AQS) as a “case study material” for the ORR.
Highlights
For decades it has been known that quinones, and especially an thraquinones, are suitable catalysts for the chemical as well as electro chemical production of hydrogen peroxide (H2O2) by the reduction of oxygen (O2) [1,2,3]
The hydrogen peroxide production (HPP) behaviour of carbon electrodes has been known for a long time [4] and the explanation for this outcome is presumed to be that reduced quinone moieties on the electrode surface are oxidized by oxygen which is transformed into H2O2 [5,6,7]
Using a standard glassy carbon (GC) electrode, it can be clearly seen from Fig. 1 that the AQS reduction curve overlaps with the oxygen reduction reaction (ORR) curve of the bare GC
Summary
For decades it has been known that quinones, and especially an thraquinones, are suitable catalysts for the chemical as well as electro chemical production of hydrogen peroxide (H2O2) by the reduction of oxygen (O2) [1,2,3]. As well as the target 2-electron reaction (O2 to H2O2) the direct 4-electron reduction to water, or reduction of H2O2 to water, can occur as competing side-reactions [3] Many metals, such as platinum, prefer the direct 4-electron reduction to water, whereas others, like gold and most carbon-based materials, show a strong tendency towards hydrogen peroxide production (HPP). The HPP behaviour of carbon electrodes has been known for a long time [4] and the explanation for this outcome is presumed to be that reduced quinone moieties on the electrode surface are oxidized by oxygen which is transformed into H2O2 [5,6,7]. Dissolved anthraquinones have been reported as redox mediators in photoelectrochemical cells (PEC) for
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