Joule heating‑driven sp2‑c domains modulation in biomass carbon for high‑performance bifunctional oxygen electrocatalysis

Biomass-derived carbon materials are poised to revolutionize oxygen electrocatalysis with their remarkable performance and cost-effectiveness. Despite the promising properties of these materials as metal-free catalysts for oxygen reduction and evolution reactions, their application has been limited by suboptimal catalytic performance due to the lack of effective modulating strategies. Now, researchers from Nanjing Forestry University, Shanghai University, and the University of Cincinnati, led by Professor Liang Wang and Mengmeng Fan, have made a significant breakthrough. Their latest study titled “Joule Heating-Driven sp²-C Domains Modulation in Biomass Carbon for High-Performance Bifunctional Oxygen Electrocatalysis” presents a novel approach to fabricating high-performance electrocatalysts using nitrogen-doped biomass-derived carbon materials with enhanced sp²-C domains through a flash Joule heating process.

Why This Research Matters

• Enhanced ORR Performance: The flash Joule heating process significantly increases the density of sp²-C domains in nitrogen-doped biomass-derived carbon, leading to an outstanding oxygen reduction reaction (ORR) half-wave potential of 0.884 VRHE, comparable to commercial 20% Pt/C catalysts.
• Superior OER Activity: The same catalyst also exhibits excellent oxygen evolution reaction (OER) activity, with an overpotential of only 295 mV at 10 mA cm^-2, outperforming commercial RuO₂ catalysts.
• Long-Term Stability: When integrated into a Zn-air battery, the optimized catalyst achieves over 1200 hours of cycle stability with a peak power density of 121 mW cm^-2, surpassing the performance of conventional catalysts.

Innovative Joule Heating Process and Mechanisms

• Unique Fabrication Process: The team used a flash Joule heating process to enhance the sp²-C domain content in nitrogen-doped activated carbon derived from coconut shells. This process not only increases the graphitization degree but also optimizes the electronic structure of nitrogen configurations, leading to improved catalytic performance.
• Synergistic Effects: The enhanced sp²-C domains and nitrogen doping work synergistically to increase the density of active sites and facilitate electron transfer, resulting in superior ORR and OER performance.
• DFT Simulations: Density functional theory (DFT) calculations revealed that the axial regulation of sp²-C domains optimizes the electronic states of active carbon sites, providing mechanistic insights into the enhanced catalytic activity.

Future Outlook

• Scalability and Practicality: The flash Joule heating process is scalable and can be applied to various biomass-derived carbon materials, offering a versatile strategy for developing high-performance electrocatalysts.
• Energy Storage Applications: The exceptional performance of the optimized catalyst in Zn-air batteries highlights its potential for practical applications in energy storage systems, where long-term stability and high power density are crucial.
• Further Optimization: Future research may focus on further optimizing the Joule heating conditions and exploring other biomass sources to maximize catalytic performance while maintaining cost-effectiveness.

Stay tuned for more groundbreaking advancements from Professor Liang Wang, Mengmeng Fan and the team as they continue to push the boundaries of electrocatalysis technology!