Molybdenum‐based compounds are considered as a potential replacement for expensive precious‐metal electrocatalysts for the hydrogen evolution reaction (HER) in acid electrolytes. However, coating of thin films of molybdenum nitride or carbide on a large‐area self‐standing substrate with high precision is still challenging. Here, MoN_x is uniformly coated on carbon cloth (CC) and nitrogen‐doped carbon (NC)‐modified CC (NCCC) substrates by atomic layer deposition (ALD). The as‐deposited film has a nanocrystalline character close to amorphous and a composition of approximately Mo₂N with significant oxygen contamination, mainly at the surface. Among the as‐prepared ALD‐MoN_x electrodes, the MoN_x/NCCC has the highest HER activity (overpotential η≈236 mV to achieve 10 mA cm⁻²) owing to the high surface area and porosity of the NCCC substrate. However, the durability of the electrode is poor, owing to the poor adhesion of NC powder on CC. Annealing MoN_x/NCCC in H₂ atmosphere at 400 °C improves both the activity and durability of the electrode without significant change in the phase or porosity. Annealing at an elevated temperature of 600 °C results in formation of a Mo₂C phase that further enhances the activity (η≈196 mV to achieve 10 mA cm⁻²), although there is a huge reduction in the porosity of the electrode as a consequence of the annealing. The structure of the electrode is also systematically investigated by electrochemical impedance spectroscopy (EIS). A deviation in the conventional Warburg impedance is observed in EIS of the NCCC‐based electrode and is ascribed to the change in the H⁺ ion diffusion characteristics, owing to the geometry of the pores. The change in porous nature with annealing and the loss in porosity are reflected in the EIS of H⁺ ion diffusion observed at high‐frequency. The current work establishes a better understanding of the importance of various parameters for a highly active HER electrode and will help the development of a commercial electrode for HER using the ALD technique.

中文翻译：

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多孔碳基底上原子层沉积的MoNx引起的氢气析出反应：孔隙率和退火对催化剂活性和稳定性的影响。

钼基化合物被认为可以替代昂贵的贵金属电催化剂，用于酸性电解质中的氢释放反应（HER）。但是，在大面积自立式基板上以高精度涂覆氮化钼或碳化钼薄膜仍然是一项挑战。在这里，MoN _x通过原子层沉积（ALD）均匀地涂覆在碳布（CC）和掺氮碳（NC）改性的CC（NCCC）基底上。沉积后的薄膜具有接近无定形的纳米晶体特性，并且主要在表面上具有约Mo ₂ N的组成，且氧污染严重。在准备好的ALD-MoN _x电极中，MoN _x/ NCCC具有最高的HER活性（过电压η ≈236毫伏达到10毫安厘米^-2由于NCCC基板的高的表面积和孔隙率）。但是，由于NC粉末在CC上的粘附性差，因此电极的耐久性差。在400°C的H ₂气氛中对MoN _x / NCCC进行退火可改善电极的活性和耐用性，而不会明显改变相或孔隙率。退火在升高的温度为600℃导致形成的Mo ₂ C相，进一步增强了该活性（η ≈196毫伏达到10毫安厘米^-2），尽管由于退火导致电极的孔隙率大大降低。电极的结构也通过电化学阻抗谱（EIS）进行了系统研究。在基于NCCC的电极的EIS中观察到常规Warburg阻抗存在偏差，这归因于孔的几何形状，H ⁺离子扩散特性发生了变化。高频下观察到的H ⁺离子扩散的EIS反映了多孔性质随退火的变化以及孔隙率的损失。当前的工作使人们对高活性HER电极的各种参数的重要性有了更好的了解，并将有助于使用ALD技术开发用于HER的商用电极。