Rational design and mass-scale synthesis of guar-derived bifunctional oxygen catalyst for rechargeable Zn-air battery with active sites validation

The development of bifunctional OER and ORR catalysts for reversible energy storage is challenging due to the requirement of both catalytic activity and stability in a broad potential range. Under the circumstance, rational catalyst design based on fundamental understanding of redox-active sites becomes particularly meaningful. Herein, we report a facile and low-cost approach utilizing natural guar gum to fabricate a high-performance bifunctional catalyst in mass scale incorporating both the CoP and Co-N-C moieties to afford simultaneous OER and ORR activities that are comparable to RuO2 and Pt/C, respectively. Through exquisitely performed control studies, post-reaction analyses, and operando investigations, the OER and ORR active sites are validated as per initial catalyst design. Rechargeable Zinc-air batteries are further demonstrated manifesting energy efficiency, cycling stability, and high power density. This study marks the power of rational catalyst design by contriving redox-targeting moieties into hierarchical carbon scaffold to impart the desired functionalities.