Increasing the number of active sites of polymer-assisted carbon nanotubes/Ag nanoparticles for enhanced oxygen reduction

Increasing the number of electroactive sites to enhance catalytic activity is by far the best approach for enhancing the oxygen reduction reaction; however, the development of a catalyst with high electrochemical performance and long-term stability remains a significant challenge because of the weak binding energy of oxygenated species. Herein, we report the fabrication of an extended Ag nanoparticle network on a defect-rich carbon nanotube (CNT) ternary composite, CNT@pPPD-Ag, derived from polyparaphenylenediamine (pPPD) with a porous crystalline framework that enhances the edge-rich N-species-decorated carbon nanotubes. The N-bridged-polymer/CNT composite facilitates the aligned dispersion of Ag nanoparticles anchored at the low coordination sites, increases the surface area and pore size volume, and exposes effective CNT-N-Ag active sites for enhanced oxygen absorption to convert O-2 into H2O. In addition, the reduced electron delocalization around the Ag atoms due to the N-species enhances the charge interaction between the neighboring N and Ag atoms, leading to the strengthening of the interaction with the adsorbed oxygen species, thereby increasing the intrinsic activity of each electroactive site. In this work, CNT@pPPD-Ag composite explored with remarkable low onset potential (-0.041 V) and limiting current density (-5.80 mA cm(-2)) in an alkaline environment, and far exceeds the performance of expensive Pt/C catalysts.

Automated summary

By introducing an extended Ag nanoparticle network on the surface of carbon nanotubes, the number of electroactive sites is increased, significantly enhancing the catalytic activity of the oxygen reduction reaction; in addition, N-species modification can strengthen the charge interaction between neighboring N and Ag atoms, enhance the interaction with adsorbed oxygen species, further increasing the intrinsic activity of each electroactive site.