Modulating the aqueous hydrogen evolution activity of bioinspired diiron electrocatalyst immobilized on carbon nanotubes through various attaching strategy

Abstract

Bioinspired chemistry of [FeFe]-hydrogenases with efficient catalytic hydrogen evolution reaction (HER) ability has attracted significant attention in the field of electrochemical water splitting into hydrogen (H₂). Herein, this work describes the immobilization of diiron dithiolate (2Fe2S) molecules onto carbon nanotubes (CNTs) through different interfacial attachment and the electrocatalytic HER properties in neutral water. First of all, one all-carbonyl 2Fe2S precursor Fe₂(μ-pdt)CO₆ [pdt = (SCH₂)₂CH₂, (1)] and its two new PN^RP-bridged derivatives Fe₂(μ-pdt)CO₄(μ-PN^RP) [PN^RP = (Ph₂P)₂NR; R = NHCH₂pyrene (2) and NHCH₂Ph (3)] were prepared and could be further grafted covalently versus non-covalently to CNTs to form three desired 2Fe2S/CNT hybrids labeling as CNT-1 with covalent bond, CNT-2 via π-π stacking, and CNT-3 via physisorption. Meanwhile, the structural characterizations of diiron molecules 2, 3 and CNT-supported hybrids CNT-X (X = 1, 2, 3) are well performed by means of elemental analysis, various spectroscopies, and especially for 2, 3 by X-ray crystallography. Notably, the electrocatalytic HER activity trend of CNT-1 > CNT-2 > CNT-3 is found in 0.1 M phosphate buffer solution (pH = 7) using various electrochemical measurements but the degradation of diiron core in them results in the electrocatalytic deactivations in the long-term electrolysis. Overall, this study is meaningful to extend the practical application of carbon support electrodes integrated with bioinspired diiron electrocatalysts for heterogeneous HER in water.