Biomorphic CoNC/CoO_x Composite Derived from Natural Chloroplasts as Efficient Electrocatalyst for Oxygen Reduction...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Chlorophylls (magnesium porphyrin, Mg-Chl) are abundant natural pigments.
• Developing efficient and durable electrocatalysts for the oxygen reduction reaction (ORR) is crucial for energy technologies.
• Biomorphic materials offer unique structural advantages for catalyst design.

Purpose of the Study:

• To synthesize a biomorphic cobalt-nitrogen-carbon/cobalt oxide (CoN C/CoOₓ) composite electrocatalyst using natural chloroplasts.
• To investigate the electrocatalytic performance of the synthesized material for the oxygen reduction reaction (ORR).
• To explore a novel approach for creating advanced electrocatalysts by integrating bioderivative components and bioarchitectures.

Main Methods:

• Chloroplasts were treated with hydrochloric acid and cobalt acetate to obtain cobalt-substituted chlorophyll derivatives (Co-Chl).
• Calcination of Co-Chl in a nitrogen atmosphere at 800 °C converted it to CoN C, while cobalt-adsorbed chloroplasts formed CoOₓ.
• The resulting CoN C/CoOₓ composite was characterized and tested for ORR electrocatalytic activity.

Main Results:

• The synthesized biomorphic CoN C/CoOₓ composite retained the microarchitecture of chloroplasts.
• Abundant active CoN C sites were protected by carbon and CoOₓ, preventing agglomeration and enhancing conductivity.
• The electrocatalyst exhibited excellent ORR performance with onset potential of 0.89 V and half-wave potential of 0.82 V vs. RHE, superior durability, and methanol tolerance compared to commercial Pt/C.

Conclusions:

• Natural chloroplasts can serve as both a template and porphyrin source for synthesizing high-performance biomorphic electrocatalysts.
• The synergistic effect between CoN C and CoOₓ, coupled with the bioarchitecture, significantly boosts ORR electrocatalytic activity.
• This study presents a novel strategy for designing integrated electrocatalyst systems by combining bioderivative components and bioarchitectures.