Abstract
The influence of the types and amounts of oxygen (O), nitrogen (N), and/or phosphorus (P) heteroatoms on the surface of carbon nanotubes (CNTs) on stability and catalytic activity in the oxygen reduction reaction (ORR) was investigated in alkaline media. It is shown that functionalization of CNTs leads to growth of the electrochemically active surface and to an increase in activity in the ORR. At the same time, a decrease in stability is observed after functionalization of CNTs under accelerated corrosion testing in alkaline media. These results are most significant on CNTs after functionalization in HNO3, due to the formation of a large number of structural defects. However, subsequent doping with N and/or P atoms provides a further activity increase and enhances the corrosion stability of CNTs. Thus, as shown by the studies of characteristic parameters (electrochemical active surface values (SEAS); E1/2; corrosion stability), CNTs doped with N and NP are promising catalytic systems that can be recommended for use as fuel cell cathodes. An important condition for effective doping is the synthesis of carboxyl and carbonyl oxygen-containing groups on the surface of CNTs.
Highlights
Oxygen electroreduction is one of the most important reactions due to widespread demand for its practical use
X-ray Photoelectron Spectrum (XPS) Studies In Figure 1a, the effect on the structure of the initial carbon nanotubes (CNTs) was insignificant after treatment in
The electron binding showed that N was present showed that upon doping, thecarbon number of oxygen-containing groups energy decreased, and heteroatoms were in the form of pyrrole and pyridine and was bonded to two atoms, based on comparison incorporated into the carbon structure
Summary
Oxygen electroreduction is one of the most important reactions due to widespread demand for its practical use. The development of active and stable catalysts for the cathodic oxygen reduction reaction is a priority problem for the production of fuel cells (FC) and metal-air batteries [1,2]. Among such systems, alkaline FCs operating with high efficiency at atmospheric pressure in a wide temperature range are of particular importance [3]. A number of studies have shown that carbon nanotubes (CNTs) are promising materials for FC cathodes due to such properties as corrosion stability, large specific surface area, and high electric conductivity [1,4]. The introduction of Catalysts 2020, 10, 892; doi:10.3390/catal10080892 www.mdpi.com/journal/catalysts
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