Electrochemical Degradation of Multiwall Carbon Nanotubes at High Anodic Potential for Oxygen Evolution in Acidic Media

Abstract

There is great interest in electrochemical water splitting for the efficient utilization of sustainable energy. As an alternative to high-priced materials, carbon offers considerable potential. However, carbon is limited as an electrode material for the oxygen evolution reaction (OER), owing to its thermodynamic instability against electrochemical oxidation. In this study, we investigated the electrochemical degradation of multiwall carbon nanotubes (MWCNTs) under the acidic OER environment. Electrochemical oxidation of MWCNTs induces structural changes and the formation of oxygen-containing functional groups on the carbon surface. As a consequence, the electrochemical and physicochemical properties of the MWCNTs are changed during electrochemical oxidation. We carried out electrochemical, microstructural, and spectroscopic analysis to investigate the degradation of MWCNTs. By changing of the electrochemical properties of MWCNTs during the oxidation process, the carbon electrode is initially activated and can then be kinetically stabilized with prolonged oxidation under the OER conditions

MAXNET Energy – Focusing Research in Chemical Energy Conversion on the Electrocatlytic Oxygen Evolution

“…Different water electrolysis technologies are currently discussed as options to handle intermittent electricity supply originating from renewable energy sources [54,55]. Final disclosure (if any) about the "best" technology can be only answered in the system framework where the whole pathway from raw water to pressurized hydrogen, including all pre-and post-processing steps, has to be considered.…”

“…Additionally, catalyst layers should provide sufficiently high ionic and electronic conductivities. All these requirements are difficult to satisfy using current methods for catalyst layer preparation, which often lead to low catalyst utilization, and thus the necessity to use high catalyst loadings which contribute significantly to the electrolyser cost [54]. For this reason, the development of novel strategies for the preparation of tailor-made high-performance catalyst layers has very high practical relevance.…”

Carbon Nanotubes as a Solid Acid Fuel Cell Cathode Material: Insights into In Operando Functional Stability

“…[31,32] Electrochemical degradation of MWCNTs induces both structural and physico-chemical changes such as surface defects and oxidation. [31,34] In summary, improved electrochemical performance can be observed when measuring ORR activity for extremely high specific surface area carbon nanomaterials but they are most likely accompanied by quick changes of the surface and degradation. In contrast, high specific surface area carbon nanomaterials suffer from much higher degradation rates.…”

“…Nevertheless, relatively slow kinetics and high loadings of cheap carbon allow them to be used as electronic interconnects. [31][32][33][34][35][36] However, reaction pathways and active sites depend heavily on the environment of the catalyst, such as acidity of the electrolyte, temperature, the presence of water etc. [33] The formation of hydrogen peroxide and the oxidation of the carbon nanomaterial generates charge carriers and might be mistaken for ORR activity.…”

Nitrogenated‐Graphite‐Encapsulated Carbon Black as a Metal‐Free Electrocatalyst for the Oxygen Evolution Reaction in Acid

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No metal needed: A core-shell-like carbon catalyst consisting of a few layers of nitrogen-doped graphite on a carbon black core was prepared by pyrolyzing an ionic liquid (IL) with carbon black (CB) particles. [10][11] In 2016, the Xu group reported that a nitrogen, phosphorus and oxygen triply-doped/functionalized carbon cloth was active and stable for OER in acid solution. The resilience of the catalyst in acid solution is due to the greater protection of the nitrogen-containing OER active sites in a graphitic shell.

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