Abstract
Nitrogen (N)-doped nanostructured carbons have been actively examined as promising alternatives for precious-metal catalysts in various electrochemical energy generation systems. Herein, an effective approach for synthesizing N-doped single-walled carbon nanohorns (SWNHs) with highly electrocatalytic active sites via controlled oxidation followed by N2 plasma is presented. Nanosized holes were created on the conical tips and sidewalls of SWNHs under mild oxidation, and subsequently, the edges of the holes were easily decorated with N atoms. The N atoms were present preferentially in a pyridinic configuration along the edges of the nanosized holes without significant structural change of the SWNHs. The enriched edges decorated with the pyridinic-N atoms at the atomic scale increased the number of active sites for the oxygen reduction reaction, and the inherent spherical three-dimensional feature of the SWNHs provided good electrical conductivity and excellent mass transport. We demonstrated an effective method for promoting the electrocatalytic active sites within N-doped SWNHs by combining defect engineering with the preferential formation of N atoms having a specific configuration.
Highlights
Nitrogen (N)-doped nanostructured carbons have been actively examined as promising alternatives for precious-metal catalysts in various electrochemical energy generation systems
The single-walled carbon nanohorns (SWNHs) and Oxidized SWNHs (O-SWNHs) were mainly composed of carbon (C) and oxygen (O) (Fig. 1(e,i,g,k)), whereas N was identified in the N2 plasma-treated samples (Fig. 1(n,p))
Even though the oxidation did not change the type of the N2 adsorption isotherm, we observed a significantly increased amount of N2 adsorbed in the O-SWNHs at a lower relative pressure than the pristine sample
Summary
Nitrogen (N)-doped nanostructured carbons have been actively examined as promising alternatives for precious-metal catalysts in various electrochemical energy generation systems. An effective approach for synthesizing N-doped single-walled carbon nanohorns (SWNHs) with highly electrocatalytic active sites via controlled oxidation followed by N2 plasma is presented. Nanosized holes were created on the conical tips and sidewalls of SWNHs under mild oxidation, and subsequently, the edges of the holes were decorated with N atoms. The physical and chemical properties of carbon materials such as the electrical conductivity, chemical activity, and porosity can be tailored by selective introduction of chemical moieties and defects on the conical edges and sidewalls of SWNHs. Nitrogen (N)-doped carbon nanomaterials have been actively evaluated as promising alternatives for precious-metal catalysts in various electrochemical energy generation systems[10]. The N-doped defective SWNHs with pyridine rich configurations exhibited significantly improved electrocatalytic performance while retaining their initial structure
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