From Chlorella to Nestlike Framework Constructed with Doped Carbon Nanotubes: A Biomass-Derived, High-Performance, Bifunctional Oxygen Reduction/Evolution Catalyst

Abstract

The development of effective bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is significant for energy conversion systems, such as Li-air batteries, fuel cells, and water splitting technologies. Herein, a Chlorella-derived catalyst with a nestlike framework, composed of bamboolike nanotubes that encapsulate cobalt nanoparticles, has been prepared through a facile pyrolysis process. It achieves perfect bifunctional catalysis both in ORR and OER on a single catalyst. For our optimal catalyst Co/M-Chlorella-900, its ORR half-wave potential is positively shifted by 40 mV compared to that of a commercial Pt/C catalyst, and the overpotential at 10 mA cm for the OER is 23 mV lower than that of a commercial IrO/C catalyst in an alkaline medium. This superior bifunctional catalytic performance is benefited from the simultaneous increase of pyridinic N sites for ORR and graphitic N sites for OER. In addition, N-doped carbon-encapsulated Co nanoparticles improve both ORR and OER performance by forming new active centers. The unique nestlike carbon nanotube framework not only afforded highly dense ORR and OER active sites but also promoted the electron and mass transfer. Our catalyst also displays notable durability during the ORR and OER, making it promising for use in ORR/OER-related energy conversion systems.

Sustainable Battery Materials from Biomass

“…Similarly, all kinds of biowaste have been carbonized and used as host materials in the cathodes of lithium–sulfur, lithium–selenium, or lithium–oxygen batteries. Within recent years, for example, carbons made from waste materials such as fruit stones or peels, algae, nutshells, soybean hulls, grain waste, other plant waste, saw dust, and lignin have been described in this regard.…”

“…Carbons made from biomass often naturally benefit from nitrogen doping due to the presence of nitrogen in many bioresources and are thus especially appealing. In cases where N‐doping from the carbon precursor is not sufficient, other nitrogen containing precursors like melamine, which can be synthesized from sustainable resources, may be added before carbonization . To decrease the overpotential and increase the efficiency of the ORR/OER, biomass‐based carbons may also be impregnated with metal ions or particles .…”

“…In cases where N‐doping from the carbon precursor is not sufficient, other nitrogen containing precursors like melamine, which can be synthesized from sustainable resources, may be added before carbonization . To decrease the overpotential and increase the efficiency of the ORR/OER, biomass‐based carbons may also be impregnated with metal ions or particles . The remaining synthesis steps are similar to the above‐described processes.…”

Sponge-like N-doped carbon materials with Co-based nanoparticles derived from biomass as highly efficient electrocatalysts for the oxygen reduction reaction in alkaline media

“…Together these results indicate that CoO indeed exits in catalysts of CoNASS, which could function to enhance the electron transfer and ORR performance. 46,47 To further investigate the contents and chemical states of the elements in the as-prepared carbon samples, XPS was conducted ( Fig. S4 †).…”

Nitrogen and Cobalt Co-Coped Carbon Materials Derived from Biomass Chitin as High-Performance Electrocatalyst for Aluminum-Air Batteries

“…Biomass materials are the ideal carbon precursor for synthesizing ORR catalysts due to their renewability and large-scale and low-cost production [18][19][20][21][22][23][24][25]. Recently, several studies reported biomass-derived ORR catalysts with efficient catalytic activities.…”