Development of platinum group metal (PGM)-free and iron-free catalysts for the kinetically sluggish oxygen reduction reaction (ORR) is crucial for proton-exchange membrane fuel cells. A major challenge is their insufficient performance and durability in the membrane electrode assembly (MEA) under practical hydrogen-air conditions. Herein, we report an effective strategy to synthesize atomically dispersed Mn–N–C catalysts from an environmentally benign aqueous solution, instead of traditional organic solvents. This innovative synthesis method yields an extremely high surface area for accommodating an increased density of MnN₄ active sites, which was verified by using advanced electron microscopy and X-ray absorption spectroscopy. The Mn–N–C catalyst exhibits promising ORR activity along with significantly enhanced stability, achieving a peak power density of 0.39 W cm^–2 under 1.0 bar H₂-air condition in a MEA, outperforming most PGM-free ORR catalysts. The improved performance is likely due to the unique catalyst features, including the curved surface morphology and dominant graphitic carbon structure, thus benefiting mass transport and improving stability. The first-principles calculations further elucidate the enhanced stability, suggesting that MnN₄ sites have a higher resistance to demetallation than the traditional FeN₄ sites during the ORR.

中文翻译：

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通过环境友好的水性合成减少氧原子分散的MnN ₄催化剂：机理的活性和稳定性改善的理解。

开发用于动力学迟缓的氧还原反应（ORR）的不含铂族金属（PGM）和不含铁的催化剂对于质子交换膜燃料电池至关重要。主要的挑战是它们在实际的氢气环境下在膜电极组件（MEA）中的性能和耐久性不足。在此，我们报告了一种有效的策略，该方法可从对环境无害的水溶液中代替传统的有机溶剂来合成原子分散的Mn–N–C催化剂。这种创新的合成方法可产生极高的表面积，以适应增加的MnN ₄密度活性位点，已通过先进的电子显微镜和X射线吸收光谱法进行了验证。Mn–N–C催化剂显示出有希望的ORR活性以及显着增强的稳定性，在MEA中在1.0 bar H _2的空气条件下，峰值功率密度为0.39 W cm ^–2，优于大多数不含PGM的ORR催化剂。改进的性能可能归因于独特的催化剂功能，包括弯曲的表面形态和主要的石墨碳结构，从而有利于传质并提高了稳定性。第一性原理的计算进一步阐明了增强的稳定性，表明在ORR期间MnN ₄位比传统FeN ₄位具有更高的抗脱金属能力。