{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T13:39:25Z","timestamp":1779889165527,"version":"3.53.1"},"reference-count":51,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2023,12,19]],"date-time":"2023-12-19T00:00:00Z","timestamp":1702944000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Natural Science Research Project of Shanxi Basic Research Program","award":["202203021221141"],"award-info":[{"award-number":["202203021221141"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>A metal-free carbon catalyst is a kind of oxygen reduction catalyst with great prospects. It is an important material with potential to replace the traditional Pt catalyst. In this paper, a kind of irregular and ultra-thin carbon nanosheet (K180M-300-900) with high catalytic activity was synthesized by hydrothermal calcination using okra as a biomass and NH4Cl as an N source. The prepared nitrogen-doped metal-free catalyst with high pyridine-N and graphitic-N provides an extremely large number of active sites and has certain lattice defects. Ultra-thin carbon nanosheets promote sufficient contact between the catalyst and electrolyte, promote the diffusion of oxygen, and result in a faster transfer rate of electrons. The initial potential and half-slope potential of K180M-300-900 are 0.99 V and 0.82 V, respectively, which are comparable to those of 20% Pt\/C. In addition, the stability and methanol tolerance of this catalyst (K180M-300-900) are better than 20% Pt\/C, so it has great development potential and application value. This result provides a new method to prepare metal-free carbon materials that will take the place of traditional Pt catalysts.<\/jats:p>","DOI":"10.3390\/molecules29010003","type":"journal-article","created":{"date-parts":[[2023,12,19]],"date-time":"2023-12-19T04:18:37Z","timestamp":1702959517000},"page":"3","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Highly Efficient Oxygen Reduction N-Doped Carbon Nanosheets Were Prepared by Hydrothermal Carbonization"],"prefix":"10.3390","volume":"29","author":[{"given":"Yuchen","family":"Liu","sequence":"first","affiliation":[{"name":"School of Physics and Information Engineering, Shanxi Normal University, No.339 Taiyu Road, Xiaodian District, Taiyuan 030031, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yajie","family":"Zheng","sequence":"additional","affiliation":[{"name":"School of Physics and Information Engineering, Shanxi Normal University, No.339 Taiyu Road, Xiaodian District, Taiyuan 030031, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peiyun","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Physics and Information Engineering, Shanxi Normal University, No.339 Taiyu Road, Xiaodian District, Taiyuan 030031, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7644-8942","authenticated-orcid":false,"given":"Junhua","family":"Hou","sequence":"additional","affiliation":[{"name":"School of Physics and Information Engineering, Shanxi Normal University, No.339 Taiyu Road, Xiaodian District, Taiyuan 030031, China"},{"name":"Extreme Optical Collaborative Innovation Center, Shanxi University, No. 92, Wucheng Road, Xiaodian District, Taiyuan 030006, China"},{"name":"Modern College of Humanities and Sciences, Shanxi Normal University, No.501 Binhe West Road, Yaodu District, Linfen 041000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,12,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"334","DOI":"10.1016\/j.nanoen.2017.01.045","article-title":"A versatile biomass derived carbon material for oxygen reduction reaction, supercapacitors and oil\/water separation","volume":"33","author":"Gao","year":"2017","journal-title":"Nano Energy"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"560","DOI":"10.1016\/j.jechem.2021.08.066","article-title":"Pollen-like self-supported FeIr alloy for improved hydrogen evolution reaction in acid electrolyte","volume":"66","author":"Ma","year":"2022","journal-title":"J. Energy Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"eaad4998","DOI":"10.1126\/science.aad4998","article-title":"Combining theory and experiment in electrocatalysis: Insights into materials design","volume":"355","author":"Seh","year":"2017","journal-title":"Science"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"e1806545","DOI":"10.1002\/adma.201806545","article-title":"Progress in the Development of Fe-Based PGM-Free Electrocatalysts for the Oxygen Reduction Reaction","volume":"31","author":"Martinez","year":"2019","journal-title":"Adv. Mater."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"5656","DOI":"10.1002\/smll.201600977","article-title":"Nanostructured Bifunctional Redox Electrocatalysts","volume":"12","author":"Kuang","year":"2016","journal-title":"Small"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1016\/j.apsusc.2018.09.185","article-title":"Bifunctional biomass-derived 3D nitrogen-doped porous carbon for oxygen reduction reaction and solid-state supercapacitor","volume":"465","author":"He","year":"2019","journal-title":"Appl. Surf. Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2172","DOI":"10.1039\/c1cs15228a","article-title":"Metal-air batteries: From oxygen reduction electrochemistry to cathode catalysts","volume":"41","author":"Cheng","year":"2012","journal-title":"Chem. Soc. Rev."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"203","DOI":"10.1016\/j.ensm.2020.09.011","article-title":"Stable aqueous Zn\u2212Ag and Zn\u2212polyoxometalate hybrid battery driven by successive Ag+ cation and polyoxoanion redox reactions","volume":"34","author":"Yang","year":"2021","journal-title":"Energy Storage Mater."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"11153","DOI":"10.1002\/anie.202017318","article-title":"Multicomponent Self-Assembly of a Giant Heterometallic Polyoxotungstate Supercluster with Antitumor Activity","volume":"60","author":"Liu","year":"2021","journal-title":"Angew. Chem. Int. Ed. Engl."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e202206460","DOI":"10.1002\/anie.202206460","article-title":"Highly Active Si Sites Enabled by Negative Valent Ru for Electrocatalytic Hydrogen Evolution in LaRuSi","volume":"61","author":"Shen","year":"2022","journal-title":"Angew. Chem. Int. Ed. Engl."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"118188","DOI":"10.1016\/j.apcatb.2019.118188","article-title":"Co single-atom anchored on Co3O4 and nitrogen-doped active carbon toward bifunctional catalyst for zinc-air batteries","volume":"260","author":"Zhong","year":"2020","journal-title":"Appl. Catal. B Environ."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1016\/j.carbon.2019.02.006","article-title":"Bottom-up synthesis of MOF-derived hollow N-doped carbon materials for enhanced ORR performance","volume":"146","author":"Chai","year":"2019","journal-title":"Carbon"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"e1807615","DOI":"10.1002\/adma.201807615","article-title":"PGM-Free Cathode Catalysts for PEM Fuel Cells: A Mini-Review on Stability Challenges","volume":"31","author":"Shao","year":"2019","journal-title":"Adv. Mater."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"337","DOI":"10.1039\/C6CS00328A","article-title":"Electrocatalysis for the oxygen evolution reaction: Recent development and future perspectives","volume":"46","author":"Suen","year":"2017","journal-title":"Chem. Soc. Rev."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"552","DOI":"10.1038\/nchem.367","article-title":"Alloys of platinum and early transition metals as oxygen reduction electrocatalysts","volume":"1","author":"Greeley","year":"2009","journal-title":"Nat. Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"6606","DOI":"10.1039\/C9CY01597C","article-title":"N-doped hierarchical porous metal-free catalysts derived from covalent triazine frameworks for the efficient oxygen reduction reaction","volume":"9","author":"Cao","year":"2019","journal-title":"Catal. Sci. Technol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"76","DOI":"10.1016\/j.apsusc.2018.12.293","article-title":"N, P dual-doped multi-wrinkled nanosheets prepared from the egg crude lecithin as the efficient metal-free electrocatalyst for oxygen reduction reaction","volume":"476","author":"Xian","year":"2019","journal-title":"Appl. Surf. Sci."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"133730","DOI":"10.1016\/j.cej.2021.133730","article-title":"Carbon tube-graphene heterostructure with different N-doping configurations induces an electrochemically active-active interface for efficient oxygen electrocatalysis","volume":"431","author":"Zhao","year":"2022","journal-title":"Chem. Eng. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"408","DOI":"10.1016\/j.jpowsour.2018.12.047","article-title":"Biomolecule-derived N\/S co-doped CNT-graphene hybrids exhibiting excellent electrochemical activities","volume":"413","author":"Huang","year":"2019","journal-title":"J. Power Sources"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"153908","DOI":"10.1016\/j.jallcom.2020.153908","article-title":"B, N Co-Doped ordered mesoporous carbon with enhanced electrocatalytic activity for the oxygen reduction reaction","volume":"824","author":"Zeng","year":"2020","journal-title":"J. Alloys Compd."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1324","DOI":"10.1016\/j.energy.2017.11.083","article-title":"An effective strategy for the preparation of nitrogen-doped carbon from Imperata cylindrica panicle and its use as a metal-free catalyst for the oxygen reduction reaction","volume":"141","author":"Yuan","year":"2017","journal-title":"Energy"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1039\/C8EE03276A","article-title":"Defect-rich and ultrathin N doped carbon nanosheets as advanced trifunctional metal-free electrocatalysts for the ORR, OER and HER","volume":"12","author":"Jiang","year":"2019","journal-title":"Energy Environ. Sci."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"17039","DOI":"10.1021\/acssuschemeng.9b02964","article-title":"Biomass Waste-Derived 3D Metal-Free Porous Carbon as a Bifunctional Electrocatalyst for Rechargeable Zinc\u2013Air Batteries","volume":"7","author":"Li","year":"2019","journal-title":"ACS Sustain. Chem. Eng."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"904","DOI":"10.1016\/j.ijbiomac.2022.04.063","article-title":"Magnesium lignosulfonate-derived N, S co-doped 3D flower-like hierarchically porous carbon as an advanced metal-free electrocatalyst towards oxygen reduction reaction","volume":"209","author":"Yan","year":"2022","journal-title":"Int. J. Biol. Macromol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"J3148","DOI":"10.1149\/2.0201815jes","article-title":"Enhancement of Oxygen Reduction Performance of Biomass-Derived Carbon through Co-Doping with Early Transition Metal","volume":"165","author":"Dong","year":"2018","journal-title":"J. Electrochem. Soc."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"6136","DOI":"10.1039\/C5NR00013K","article-title":"Biomass-derived nitrogen self-doped porous carbon as effective metal-free catalysts for oxygen reduction reaction","volume":"7","author":"Liu","year":"2015","journal-title":"Nanoscale"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"4824","DOI":"10.1039\/C6GC01172A","article-title":"Biomass-derived carbon: Synthesis and applications in energy storage and conversion","volume":"18","author":"Deng","year":"2016","journal-title":"Green. Chem."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"e1703691","DOI":"10.1002\/adma.201703691","article-title":"Advanced Biomass-Derived Electrocatalysts for the Oxygen Reduction Reaction","volume":"30","author":"Borghei","year":"2018","journal-title":"Adv. Mater."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.carbon.2019.09.056","article-title":"Porous carbon nanosheets from biological nucleobase precursor as efficient pH-independent oxygen reduction electrocatalyst","volume":"156","author":"Huang","year":"2020","journal-title":"Carbon"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"6827","DOI":"10.1021\/acscatal.8b00338","article-title":"Graphitic Nitrogen Is Responsible for Oxygen Electroreduction on Nitrogen-Doped Carbons in Alkaline Electrolytes: Insights from Activity Attenuation Studies and Theoretical Calculations","volume":"8","author":"Wang","year":"2018","journal-title":"ACS Catal."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1238","DOI":"10.1039\/c0ee00601g","article-title":"Low-platinum and platinum-free catalysts for the oxygen reduction reaction at fuel cell cathodes","volume":"4","author":"Morozan","year":"2011","journal-title":"Energy Environ. Sci."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1751","DOI":"10.1039\/C9EE00206E","article-title":"Emerging applications of biochar-based materials for energy storage and conversion","volume":"12","author":"Liu","year":"2019","journal-title":"Energy Environ. Sci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1016\/j.apsusc.2017.03.097","article-title":"Improving biomass-derived carbon by activation with nitrogen and cobalt for supercapacitors and oxygen reduction reaction","volume":"411","author":"Zhang","year":"2017","journal-title":"Appl. Surf. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"3375","DOI":"10.1039\/C8EE02656D","article-title":"Synergistic effect of well-defined dual sites boosting the oxygen reduction reaction","volume":"11","author":"Wang","year":"2018","journal-title":"Energy Environ. Sci."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"118198","DOI":"10.1016\/j.apcatb.2019.118198","article-title":"Boosting defective carbon by anchoring well-defined atomically dispersed metal-N4 sites for ORR, OER, and Zn-air batteries","volume":"260","author":"Cheng","year":"2020","journal-title":"Appl. Catal. B Environ."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"336","DOI":"10.1016\/j.nanoen.2016.12.057","article-title":"Facile approach for synthesis of doped carbon electrocatalyst from cellulose nanofibrils toward high-performance metal-free oxygen reduction and hydrogen evolution","volume":"32","author":"Mulyadi","year":"2017","journal-title":"Nano Energy"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1016\/j.matlet.2016.03.032","article-title":"Sustainable synthesis of N and P co-doped porous amorphous carbon using oil seed processing wastes","volume":"173","author":"Konwar","year":"2016","journal-title":"Mater. Lett."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"398","DOI":"10.1016\/j.apsusc.2018.03.106","article-title":"The promotion effects of graphitic and pyridinic N combinational doping on graphene for ORR","volume":"445","author":"Yan","year":"2018","journal-title":"Appl. Surf. Sci."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1016\/j.carbon.2016.11.014","article-title":"Active sites for oxygen reduction reaction on nitrogen-doped carbon nanotubes derived from polyaniline","volume":"112","author":"Deng","year":"2017","journal-title":"Carbon"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1765","DOI":"10.1007\/s10008-021-04947-5","article-title":"N, S-codoped porous carbon as metal-free electrocatalyst for oxygen reduction reaction","volume":"25","author":"Gao","year":"2021","journal-title":"J. Solid State Electrochem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"137712","DOI":"10.1016\/j.electacta.2021.137712","article-title":"Precursor modulated active sites of nitrogen doped graphene-based carbon catalysts via one-step pyrolysis method for the enhanced oxygen reduction reaction","volume":"370","author":"Zhang","year":"2021","journal-title":"Electrochim. Acta"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"130134","DOI":"10.1016\/j.cej.2021.130134","article-title":"Porous N, B co-doped carbon nanotubes as efficient metal-free electrocatalysts for ORR and Zn-air batteries","volume":"422","author":"Wei","year":"2021","journal-title":"Chem. Eng. J."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"113230","DOI":"10.1016\/j.jelechem.2019.113230","article-title":"Biomass-derived hierarchical honeycomb-like porous carbon tube catalyst for the metal-free oxygen reduction reaction","volume":"847","author":"Tang","year":"2019","journal-title":"J. Electroanal. Chem."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"19492","DOI":"10.1016\/j.ijhydene.2018.08.201","article-title":"Tea-leaf-residual derived electrocatalyst: Hierarchical pore structure and self nitrogen and fluorine co-doping for efficient oxygen reduction reaction","volume":"43","author":"Wu","year":"2018","journal-title":"Int. J. Hydrogen Energ"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"116909","DOI":"10.1016\/j.jelechem.2022.116909","article-title":"Solvent-free synthesis of honeycomb-like N-doped porous carbon derived from biomass pine sawdust as an efficient metal-free electrocatalyst for oxygen reduction reaction","volume":"926","author":"Chen","year":"2022","journal-title":"J. Electroanal. Chem."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"2100","DOI":"10.1016\/j.jcis.2021.10.144","article-title":"In Situ produced Co(9)S(8) nanoclusters\/Co\/Mn-S, N multi-doped 3D porous carbon derived from eriochrome black T as an effective bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries","volume":"608","author":"Sun","year":"2022","journal-title":"J. Colloid Interface Sci."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"2158","DOI":"10.1021\/acscatal.8b04381","article-title":"Boosting Oxygen Reduction Catalysis with Fe\u2013N4 Sites Decorated Porous Carbons toward Fuel Cells","volume":"9","author":"Yang","year":"2019","journal-title":"ACS Catal."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"15340","DOI":"10.1039\/C8TA04777D","article-title":"Hierarchically porous carbon materials with controllable proportion of micropore area by dual-activator synthesis for high-performance supercapacitors","volume":"6","author":"Xu","year":"2018","journal-title":"J. Mater. Chem. A"},{"key":"ref_49","first-page":"29","article-title":"Facile Synthesis of N-Doped Graphene-Like Carbon Nanoflakes as Efficient and Stable Electrocatalysts for the Oxygen Reduction Reaction","volume":"10","author":"Gu","year":"2018","journal-title":"Nanomicro Lett."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"2288","DOI":"10.1002\/celc.202100571","article-title":"Iron-Containing Nitrogen-Doped Carbon Nanomaterials Prepared via NaCl Template as Efficient Electrocatalysts for the Oxygen Reduction Reaction","volume":"8","author":"Juvanen","year":"2021","journal-title":"Chemelectrochem"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"116","DOI":"10.1016\/j.jiec.2011.11.074","article-title":"Effect of simultaneous etching and N-doping on the surface and electrochemical properties of AC","volume":"18","author":"Lim","year":"2012","journal-title":"J. Ind. Eng. Chem."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/29\/1\/3\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:41:11Z","timestamp":1760132471000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/29\/1\/3"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,12,19]]},"references-count":51,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2024,1]]}},"alternative-id":["molecules29010003"],"URL":"https:\/\/doi.org\/10.3390\/molecules29010003","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,12,19]]}}}