Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL, 61801, USA.
Nat Commun. 2023 Feb 17;14(1):905. doi: 10.1038/s41467-023-36609-7.
Significant progress has been made in the bioinorganic modeling of the paramagnetic states believed to be involved in the hydrogen redox chemistry catalyzed by [NiFe] hydrogenase. However, the characterization and isolation of intermediates involved in mononuclear Ni electrocatalysts which are reported to operate through a Ni cycle have largely remained elusive. Herein, we report a Ni complex (NCHS2)Ni(OTf)2, where NCHS2 is 3,7-dithia-1(2,6)-pyridina-5(1,3)-benzenacyclooctaphane, that is an efficient electrocatalyst for the hydrogen evolution reaction (HER) with turnover frequencies of ~3,000 s and a overpotential of 670 mV in the presence of trifluoroacetic acid. This electrocatalyst follows a hitherto unobserved HER mechanism involving C-H activation, which manifests as an inverse kinetic isotope effect for the overall hydrogen evolution reaction, and Ni/Ni intermediates, which have been characterized by EPR spectroscopy. We further validate the possibility of the involvement of Ni intermediates by the independent synthesis and characterization of organometallic Ni complexes.
在[NiFe]氢化酶催化的氢氧化还原化学中涉及的顺磁态的生物无机模型方面已经取得了重大进展。然而，据报道，通过 Ni 循环起作用的单核 Ni 电催化剂所涉及的中间体的特征和分离在很大程度上仍然难以捉摸。在此，我们报告了一种 Ni 配合物（NCHS2）Ni（OTf）2，其中 NCHS2 是 3,7-二硫代-1(2,6)-吡啶并-5(1,3)-苯并环辛烷，它是一种有效的氢析出反应（HER）电催化剂，在三氟乙酸存在下具有约 3000 s 的周转率频率和 670 mV 的过电势。该电催化剂遵循一种迄今未观察到的 HER 机制，涉及 C-H 活化，这表现为整体氢析出反应的反动力学同位素效应，以及通过电子顺磁共振（EPR）光谱表征的 Ni/Ni 中间体。我们通过独立合成和表征有机金属 Ni 配合物进一步验证了 Ni 中间体参与的可能性。
