The replacement of precious metal catalysts with pyridinic and graphitic-N sites that are earth-abundant and of low-cost and enriched with a high concentration for oxygen reduction reaction (ORR) is highly desirable. Herein, we report a facile synthesis of N-doped hollow mesoporous carbon spheres (NHSs) using tetraethyl orthosilicate (TEOS) as a silica precursor and dopamine hydrochloride (DHC) as carbon and nitrogen precursors through which uniform hollow sphere mesopores can be attained by adjusting the temperature and DHC loading. At the optimum temperature of 900 °C, a concentration ratio (0.5 mL:0.4 g) of TEOS/DHC leads to high-surface-area (1452 m²/g) carbon with pore volume (0.3 cm³/g), enriched defect sites, and a large number of pyridinic and graphitic-N sites offering an outstanding activity toward ORR. Further electrochemical studies demonstrated a positive onset potential of 0.84 V, an excellent current density of 4.9 mA/cm², and a four-electron pathway with a lower Tafel slope of 65 mV/dec, respectively.

中文翻译：

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碱性介质中氮掺杂空心介孔碳纳米球的氧还原反应

迫切需要用地球上丰富且成本低廉且富含高浓度氧的吡啶和石墨N取代贵金属催化剂进行氧还原反应（ORR）。在本文中，我们报道了使用原硅酸四乙酯（TEOS）作为二氧化硅前驱体和多巴胺盐酸盐（DHC）作为碳和氮前驱体的N掺杂空心中孔碳球（NHS）的简便合成，通过调节可实现均匀的空心球中孔温度和DHC负载。在900°C的最佳温度下，TEOS / DHC的浓度比（0.5 mL：0.4 g）导致高表面积（1452 m ² / g）的碳，孔容为（0.3 cm ³/ g），富集的缺陷位点以及大量的吡啶和石墨N位点对ORR具有出色的活性。进一步的电化学研究表明，正的起始电势为0.84 V，出色的电流密度为4.9 mA / cm ²，四电子路径的Tafel斜率较低，分别为65 mV / dec。