Transition metal nitrides present superior electrocatalytic activities on the air electrode for fuel cells or metal-air batteries. Despite that, the weak intrinsic activity and ease of aggregation have hampered their catalytic kinetic properties and practical application. Herein, vanadium nitride (VN) particles of different sizes, micron to molecular level, have been fabricated using a facile, urea-nitridation method, and embedded in an N-doped graphitic carbon aerogel electrocatalyst (VN@CA), the doped material serving as an oxidation catalyst. Having a balance of atomic-level dispersed VN clusters and a high active site density, the obtained VN@CA catalytic material exhibits enhanced catalytic efficiency for the oxygen reduction reaction (ORR), the values of onset and half-wave voltages were measured to be 0.97 V and 0.90 V, respectively, compared to Pt/C (which had voltages of 0.95 V and 0.87 V). Furthermore, the assembled Zn-air battery using VN@CA as catalyst exhibits a high-power density of 176 mW cm, a substantial specific discharge capacity of 851 mAh g at 20 mA cm, a narrow gap between charging and discharging voltages (0.73 V at 50 mA cm), and an excellent charge-discharge cycling stability, exceeding 270 cycles with a 66 % round-trip efficiency. This work confirms that the particle size and the density both are responsible for the enhanced electrochemical activity.

中文翻译：

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将氮化钒颗粒的尺寸从原子级调整到微米级作为锌空气电池的高效催化剂


过渡金属氮化物在燃料电池或金属空气电池的空气电极上表现出优异的电催化活性。尽管如此，弱的内在活性和易于聚集阻碍了它们的催化动力学性能和实际应用。在此，使用简便的尿素氮化方法制备了不同尺寸（微米到分子水平）的氮化钒（VN）颗粒，并将其嵌入氮掺杂石墨碳气凝胶电催化剂（VN@CA）中，掺杂材料用作作为氧化催化剂。所获得的VN@CA催化材料具有原子级分散的VN簇的平衡和高活性位点密度，对氧还原反应（ORR）表现出增强的催化效率，测量起始电压和半波电压值为与 Pt/C（电压为 0.95V 和 0.87V）相比，分别为 0.97V 和 0.90V。此外，使用VN@CA作为催化剂组装的锌空气电池表现出176mWcm的高功率密度，20mAcm下的放电比容量高达851mAh g，充放电电压之间的差距很窄（0.73V）。 50mAcm），以及出色的充放电循环稳定性，超过270次循环，往返效率为66%。这项工作证实了颗粒尺寸和密度都是增强电化学活性的原因。