Exploring high-performance and cost-efficient electrocatalysts with unusual metastable phase offers opportunities for improving the electrochemical hydrogen generation, while it remains a great challenge to achieve them with desirable activity and stability. Herein, we report that the doping engineering in a metastable, hexagonal-close-packed nickel (hcp Ni) electrocatalyst is a largely unrevealed yet important factor in achieving an extremely active and stable electrocatalyst toward alkaline hydrogen evolution reaction (HER). Theoretical predications and experimental results suggest that, while the stability of metastable hcp Ni electrocatalyst can be largely improved via the manganese (Mn) doping due to the lower formation energy and lattice stabilization, the MnO/hcp Ni surface promotes the HER via intrinsic favorable H₂O adsorption and fast water dissociation kinetics. Consequently, the Mn-doped hcp Ni electrocatalyst shows a small overpotential of 80 mV at 10 mA/cm² and a low Tafel slope of 68 mV/dec. The result is even approaching that of the commercial Pt/C, being one of the best reported non-noble metal HER electrocatalysts in alkaline media. Under long-term chronopotentiometry measurement, such electrocatalyst can endure at least 10 h with negligible activity decay and structure change. The present work demonstrates the dimension in boosting the electrocatalysis by doping engineering of metastable electrocatalysts.

中文翻译：

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稳定和活化亚稳镍纳米晶，用于高效氢析出电催化

探索具有异常亚稳相的高性能且具有成本效益的电催化剂，为改善电化学氢的产生提供了机会，而以理想的活性和稳定性来实现它们仍然是一个巨大的挑战。在本文中，我们报告说，亚稳，六方密堆积镍（hcp Ni）电催化剂中的掺杂工程是实现朝着碱性氢释放反应（HER）的极活泼和稳定的电催化剂的很大程度上未公开但重要的因素。理论预测和实验结果表明，虽然锰形成量和晶格稳定度较低，但通过锰（Mn）掺杂可大大改善亚稳态hcp Ni电催化剂的稳定性，而MnO / hcp Ni表面可促进HER通过固有的有利H ₂ O吸附和快速的水离解动力学。因此，Mn掺杂的hcp Ni电催化剂在10 mA / cm ^2时显示出80 mV的小过电位，在68 mV / dec的低Tafel斜率下显示。结果甚至接近商业化的Pt / C，它是碱性介质中报道最多的非贵金属HER电催化剂之一。在长期计时电位法测量下，这种电催化剂可以至少保留10小时，而活性衰减和结构变化可忽略不计。本工作证明了通过掺杂亚稳电催化剂来增强电催化的尺寸。