2D Mo1.33C i‐MXene is highly promising for electrochemical applications. Here, a synthetic strategy is reported, enabling the uniform distribution of carbon‐coated CoNi (CoNi@C) nanoparticles on the vacancy‐ordered Mo1.33C i‐MXene nanosheets, thereby fully exposing the active sites of CoNi@C. First, five novel Ga‐containing (Mo2/3R1/3)2GaC (R = Dy, Ho, Er, Tm, and Lu) i‐MAX phases are synthesized as the precursor and found to be crystallized into Cmcm structure, followed by hydrothermal etching and delamination. Subsequently, CoNi– MOF is in situ grown on derived Mo1.33C i‐MXene nanosheets. By modifying the loading mass and annealing condition, CoNi–MOF is transformed into the CoNi@C and the CoNi@C/Mo1.33C displayed outstanding hydrogen evolution reaction activity with low overpotential (73 mV at 10 mA cm−2) and small Tafel slope (84 mV dec−1). Moreover, the gravimetric capacitance is also increased from 68 F g−1 in CoNi@C to 575.1 F g−1 in CoNi@C/Mo1.33C‐50 at 0.5 A g−1. After ≈5000 cycles, activation is complete, and the specific capacitance reaches its maximum value. Additionally, the specific capacitance remains stable at 95% after additional 10 000 cycles. This work improves the catalytic and supercapacitor performance of composite nanomaterials by optimizing the distribution of active sites on Mo1.33C i‐MXene, and also extends the application of Mo1.33C i‐MXene.

中文翻译：

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源自新型 （Mo2/3R1/3）2GaC（R = Dy、Ho、Er、Tm 和 Lu）纳米层的 CoNi@C/Mo1.33C i-MXene 用于电催化析氢和超电容的电化学应用


2D Mo1.33C i-MXene 在电化学应用中非常有前途。在这里，报道了一种合成策略，使碳涂层的 CoNi （CoNi@C） 纳米颗粒均匀分布在空位有序的 Mo1.33C i-MXene 纳米片上，从而完全暴露了 CoNi@C 的活性位点。首先，以前驱体合成 5 种新型含 Ga（Mo2/3R1/3）2GaC（R = Dy、Ho、Er、Tm 和 Lu）i-MAX 固定相，发现结晶为 Cmcm 结构，然后进行水热刻蚀和分层。随后，CoNi-MOF 在衍生的 Mo1.33C i-MXene 纳米片上原位生长。通过改变负载质量和退火条件，CoNi-MOF 转化为 CoNi@C，CoNi@C/Mo1.33C 显示出出色的析氢反应活性，具有低过电位（10 mA cm-2 时为 73 mV）和小塔菲尔斜率（84 mV dec-1）。此外，在 0.5 A g-1 时，重量电容也从 CoNi@C 中的 68 F g-1 增加到 CoNi@C/Mo1.33C-50 中的 575.1 F g-1。≈5000 次循环后，激活完成，比电容达到最大值。此外，在额外的 10 000 次循环后，比电容仍稳定在 95%。这项工作通过优化 Mo1.33C i-MXene 上活性位点的分布，提高了复合纳米材料的催化和超级电容器性能，也扩展了 Mo1.33C i-MXene 的应用。