Variation of dithiolate bridges in carbon nanotube-attached diiron chelate compounds for electrocatalytic hydrogen evolution reaction

Abstract

In an effort to explore the effect of dithiolate bridges on the electrochemical hydrogen evolution reaction (HER) performances of hydrogenase-inspired catalysts under fully aqueous condition, three new diphosphine-chelate diiron molecular compounds [Fe2(μ-xdt)(CO)4(k2-(Ph2PCH2)2N(CH2CH2OH)] (labeled as 1xdt, xdt = (SCH2)2X, X = NPh (adt) vs. O (odt) vs. CH2 (pdt)) with various dithiolate bridges (i.e., xdt) were prepared and then are covalently attached onto carbon nanotubes (CNTs) to fabricate biomimetic CNT-attached hybrid catalysts labeling as CNT-f-1xdt. The intact structures of target catalysts CNT-f-1xdt have been evidenced through Raman, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Further, the electrochemical HER properties and stabilities of CNT-f-1xdt loaded onto glassy carbon electrode (GC) are studied and compared in 0.05 M phosphate buffer solution (PBS, pH of 7.4) as neutral aqueous medium by using CV, linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry. In comparison with homologues CNT-f-1odt or CNT-f-1pdt containing odt or pdt bridges, the hybrid catalyst CNT-f-1adt bearing an adt bridge is found to have the better electrocatalytic HER activity and similar stability in 0.05 M PBS. This work is significant to develop a promising generation of CNT-attached electrode materials engineered with diiron-based molecular HER catalysts for water splitting into H2.