Oxygen electrode catalysts are important as inter-conversion of O2 and H2O is crucial for energy tech-nologies.However,the sluggish kinetics of oxygen reduction and evolution reactions (ORR and OER)are a hindrance to their scalable production,whereas scarce and costly Pt and Ir/Ru-based catalysts with the highest electrocatalytic activity are commercially unviable.Since good ORR catalysts are not always efficient for OER and vice versa,so bifunctional catalysts on which OER and ORR occurs on the same elec-trode are very desirable.Alternative catalysts based on heteroatom-doped carbon nanomaterials,though showed good electrocatalytic activity yet their high cost and complex synthesis is not viable for scalable production.To overcome these drawbacks,biomass-derived heteroatom-doped porous carbons have recently emerged as low-cost,earth-abundant,renewable and sustainable environment-friendly materi-als for bifunctional oxygen catalysts.The tunable morphology,mesoporous structure and high concentra-tion of catalytic active sites of these materials due to heteroatom (N)-doping could further enhance their ORR and OER activity,along with tolerance to methanol crossover and good durability.Thus,biomass-derived heteroatom-doped porous carbons with large surface area,rich edge defects,numerous microp-ores and thin 2D nanoarchitecture could be suitable as efficient bifunctional oxygen catalysts.In the pre-sent article,synthesis,N-doping,ORR/OER mechanism and electrocatalytic performance of biomass-derived bifunctional catalysts has been discussed.The selected biomass (chitin,eggs,euonymus japoni-cas,tobacco,lysine and plant residue) except wood,act as both C and N precursor,resulting in N self-doping of porous carbons that avoids the use of toxic chemicals,thus making the synthesis a facile and environment-friendly green process.The synthetic strategy could be further optimized to develop future biomass-based N self-doped porous carbons as metal-free high performance bifunctional oxygen catalysts for commercial energy applications.Recent advances and the importance of biomass-based bifunctional oxygen catalysts in metal-air batteries and fuel cells has been highlighted.The material design,perspectives and future directions in this field are also provided.

Future Environment and Energy Research Institute,Sangmyung University,Cheonan 31066,Republic of Korea;Department of Physics,Guru Nanak Dev University,Amritsar 143005,India;Ertl Center for Electrochemistry and Catalysis,Gwangju Institute of Science and Technology,123 Cheomdangwagi-ro,Buk-gu,Gwangju 61005,Republic of Korea;Department of Green Chemical Engineering,College of Engineering,Sangmyung University,Cheonan 31066,Republic of Korea

[1]Satpal Singh Sekhon;Jaeyoung Lee;Jin-Soo Park-.Biomass-derived bifunctional electrocatalysts for oxygen reduction and evolution reaction:A review)[J].能源化学,2022(02):149-172

unviable,microp,euonymus

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