Peng Lingyi, Min Jie, Bendavid Avi, Chu Dewei, Lu Xunyu, Amal Rose, Han Zhaojun
School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
School of Materials Science & Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
ACS Appl Mater Interfaces. 2022 Sep 14;14(36):40822-40833. doi: 10.1021/acsami.2c09004. Epub 2022 Aug 29.
Hydrogen production through water electrolysis is a promising method to utilize renewable energy in the context of urgent need to phase out fossil fuels. Nickel-molybdenum (NiMo) electrodes are among the best performing non-noble metal-based electrodes for hydrogen evolution reaction in alkaline media (alkaline HER). Albeit exhibiting stable performance in electrolysis at a constant power supply (i.e., constant electrolysis), NiMo electrodes suffer from performance degradation in electrolysis at an intermittent power supply (i.e., intermittent electrolysis), which is emblematic of electrolysis powered directly by renewable energy (such as wind and solar power sources). Here we reveal that NiMo electrodes were oxidized by dissolved oxygen during power interruption, leading to vanishing of metallic Ni active sites and loss of conductivity in MoO substrate. Based on the understanding of the degradation mechanism, chromium (Cr) coating was successfully applied as a protective layer to inhibit oxygen reduction reaction (ORR) and significantly enhance the stability of NiMo electrodes in intermittent electrolysis. Further, combining experimental and Molecular Dynamics (MD) simulations, we demonstrate that the Cr coating served as a physical barrier inhibiting diffusion of oxygen, while still allowing other species to pass through. Our work offers insights into electrode behavior in intermittent electrolysis, as well as provides Cr coating as a valid method and corresponding deep understanding of the factors for stability enhancement, paving the way for the successful application of lab-scale electrodes in industrial electrolysis powered directly by renewable energy.
在迫切需要淘汰化石燃料的背景下，通过水电解制氢是一种利用可再生能源的有前景的方法。镍钼（NiMo）电极是碱性介质中析氢反应（碱性HER）性能最佳的非贵金属基电极之一。尽管在恒压供电的电解过程中（即恒电解）表现出稳定的性能，但NiMo电极在间歇供电的电解过程中（即间歇电解）会出现性能下降，而间歇电解是由可再生能源（如风能和太阳能）直接供电的电解的典型特征。在此，我们揭示了NiMo电极在断电期间被溶解氧氧化，导致金属Ni活性位点消失以及MoO基体中的导电性丧失。基于对降解机制的理解，成功应用铬（Cr）涂层作为保护层来抑制氧还原反应（ORR），并显著提高NiMo电极在间歇电解中的稳定性。此外，结合实验和分子动力学（MD）模拟，我们证明Cr涂层作为物理屏障抑制了氧的扩散，同时仍允许其他物种通过。我们的工作为间歇电解中的电极行为提供了见解，同时提供了Cr涂层作为一种有效方法以及对稳定性增强因素的相应深入理解，为实验室规模的电极在由可再生能源直接供电的工业电解中的成功应用铺平了道路。
