三明治纳米结构的合理构筑实现Fe-N基催化剂酸性环境下高效电催化氧还原

Rationally-Designed Sandwiched Nanostructures Boosting Fe-N Based Catalysts toward Efficient Oxygen Reduction Electrocatalysis in Acidic Medium

开发具有高活性和高稳定性的非贵金属酸性环境下氧还原反应的催化剂对规模化发展高效质子交换膜燃料电池具有重要意义,但也非常具有挑战性。本文提出了一种快捷的湿化学吸附、热解和后蚀刻策略,有效地将Fe团簇镶嵌在两个氮掺杂碳(NC)层之间形成具有三明治夹心的NC/Fe/NC壳层,显著提升了Fe-N基催化剂酸性环境下的氧还原反应性能.所合成的中空夹层NC/Fe/NC催化剂可以在酸性介质中表现出优异的氧还原反应活性,具有0.92V的良好起始电位和高达5.1mA/cm^(2)的扩散极限电流密度.此外,三明治结构的NC/Fe/NC催化剂在酸性环境下具有很强的甲醇耐受性和出色电化学稳定性,是极具潜力的高效质子交换膜燃料电池氧还原催化剂.同步辐射表征结合X射线光电子能谱分析表明,NC/Fe/NC催化剂的NC/Fe/NC三明治壳层中存在大量的Fe-N化学键和强的界面电子耦合作用,其对催化剂电化学活性和耐腐蚀性的提升有很大帮助,是NC/Fe/NC催化剂酸性环境下高氧还原性能的根本来源.

Thedevelopmentof acidicavailable noble-metal-free oxygen reduction reaction(ORR)catalysts with high activity and good long-term durability is of significant importance for efficient proton exchange membrane fuel cells,but is still very challenging.Herein,we develop originally a facile wet-chemical-adsorption,pyrolysis and post-etching strategy to effectively intercalate Fe clusters among two nitrogen-doped carbon(NC)layers,forming unique hollow spherical nanostructures with sandwiched NC/Fe/NC shells as an active ORR catalyst.Thanks to the sandwiched nanostructure and the active Fe-N species,this as-prepared hollow sandwiched NC/Fe/NC catalyst could present superior ORR activity in an acidic medium,with a nice onset potential of 0.92 V and decent diffusion-limited current density of~5.1 mA/cm^(2).The NC/Fe/NC catalyst manifests strong methanol tolerance and outstanding durability during a long-term acidic ORR operation,being a promising alternative to Ptbased catalysts toward efficient proton exchange membrane fuel cells.Synchrotron radiation characterizations and X-ray photoemission spectroscopy reveal at the atomic-level that the abundant robust Fe-N bonds presented in the sandwiched shells of hollow NC/Fe/NC spherical catalyst contribute substantially to high electrochemical activity and superior corrosionresistance for efficient 4e-ORR in acidic electrolyte.