A new iron(II) complex as bi-functional electrocatalyst for hydrogen evolution reaction and hydrogen peroxide sensing

Abstract

In this paper, a new Fe(II) complex, [FeCl2(BBP)]·(IPA)2 (BBP = 1,3-bis(1H-benzimidazole-2-yl)propane, IPA = isopropanol), was synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR and UV/Vis spectroscopy. The crystal analysis showed that the Fe(II) complex is mononuclear, and its Fe(II) center is four coordinate in a slightly distorted tetrahedron. The electrocatalytic activity towards HER and the electrochemical sensing performance to H2O2 of the Fe(II) complex was investigated by fabricating a composite electrode (a carbon paste electrode doped with the Fe(II) complex, Fe-CPE for short). Electrochemical studies have shown that the Fe-CPE only required a low overpotential of −0.481 V to drive the current density of 10 mA cm−2 with a smaller Tafel slope of 0.142 V dec−1 for HER in 0.5 M H2SO4 at 298 K. Additionally, Fe-CPE serves as a H2O2 sensor with superior electrocatalytic activity and a low detection limit of 0.36 μM (S/N = 3) in a linear range from 5.0 × 10−7 to 4.0 × 10−3 M in 0.5 M NaOH at −0.7 V. The above studies prove that the Fe(II) complex can be used as an effective bi-functional molecular electrocatalyst for HER and H2O2 sensing.