Si-doped carbon nanotubes as efficient metal-free electrocatalysts for O2 reduction in alkaline medium

• Novel carbon nanotubes with different silicon contents were successfully fabricated.
• Silicon doping could improve the activity of CNTs for oxygen reduction reaction.
• Activities of CNTs increase first and decrease with the increase of silicon contents.
• DFT calculations indicate the Si doping could change the electronic strucure of CNTs.

To decrease the high cost of cathodic electrocatalysts caused by platinum-based catalysts in fuel cells, a series of silicon-doped carbon nanotubes with different Si contents were synthesized by the thermolysis of trimethylphenylsilane and xylene and used as low-cost metal-free catalysts for the oxygen reduction reaction (ORR). Electrochemical tests showed that the electrocatalytic activities of the synthesized Si-doped carbon nanotubes towards the ORR all were higher than that of pure carbon nanotubes and their ORR activities did not enhance proportionally with the increase of silicon doping content in alkaline medium, indicating a promising potential for designing low-cost and efficient metal-free electrocatalysts in future alkaline fuel cell devices.

A series of Si-doped carbon nanotubes (SiCNTs) were synthesized and characterized. Electrochemical tests showed that SiCNTs-2 possessed much higher activity for the oxygen reduction reaction (ORR) in comparison to pure CNTs and other Si-containing CNTs in alkaline medium, suggesting that the silicon doping could improve the ORR activity of CNTs and the ORR activities of Si-doped CNTs tend to increase first and then decrease with the increase of silicon contents.Figure optionsDownload as PowerPoint slide