Transition metal nitride (TMN)-based nanostructures have emerged as promising materials for diverse applications in electronics, photonics, energy storage, and catalysis due to their highly desirable physicochemical properties. However, synthesizing TMN-based nanostructures with designed compositions and morphologies poses challenges, especially in the solution phase. The cation exchange reaction (CER) stands out as a versatile postsynthetic strategy for preparing nanostructures that are otherwise inaccessible through direct synthesis. Nevertheless, exploration of the CER in TMNs lags behind that in metal chalcogenides and metal phosphides. Here, we demonstrate cation exchange in colloidal metal nitride nanocrystals, employing Cu₃N nanocrystals as starting materials to synthesize Ni₄N and CoN nanocrystals. By controlling the reaction conditions, Cu₃N@Ni₄N and Cu₃N@CoN core@shell heterostructures with tunable compositions can also be obtained. The Ni₄N and CoN nanocrystals are evaluated as catalysts for the electrochemical oxygen evolution reaction (OER). Remarkably, CoN nanocrystals demonstrate superior OER performance with a low overpotential of 286 mV at 10 mA·cm^–2, a small Tafel slope of 89 mV·dec^–1, and long-term stability. Our CER approach in colloidal TMNs offers a new strategy for preparing other metal nitride nanocrystals and their heterostructures, paving the way for prospective applications.

中文翻译：

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胶体过渡金属氮化物纳米晶体中的阳离子交换

基于过渡金属氮化物（TMN）的纳米结构由于其非常理想的物理化学性质，已成为电子、光子、储能和催化等领域多种应用的有前途的材料。然而，合成具有设计成分和形貌的基于 TMN 的纳米结构提出了挑战，特别是在溶液阶段。阳离子交换反应（CER）作为一种通用的合成后策略脱颖而出，用于制备通过直接合成无法获得的纳米结构。然而，对TMNs中CER的探索落后于金属硫属化物和金属磷化物中的CER。在这里，我们展示了胶体金属氮化物纳米晶体中的阳离子交换，采用 Cu ₃ N 纳米晶体作为起始材料合成 Ni ₄ N 和 CoN 纳米晶体。通过控制反应条件，还可以获得组成可调的Cu ₃ N@Ni ₄ N和Cu ₃ N@CoN核@壳异质结构。 Ni ₄ N 和 CoN 纳米晶体作为电化学析氧反应（OER）的催化剂进行了评估。值得注意的是，CoN 纳米晶体表现出优异的 OER 性能，在 10 mA·cm ^–2下具有 286 mV 的低过电位、89 mV·dec ^–1的小塔菲尔斜率以及长期稳定性。我们在胶体 TMN 中的 CER 方法为制备其他金属氮化物纳米晶体及其异质结构提供了一种新策略，为未来的应用铺平了道路。