Rational design of FeS2 microspheres as high-performance catalyst for electrooxidation of hydrazine

Abstract

• Hydrazine is one of the raw materials of direct fuel cells, which play an important role in the field of energy, the electrocatalysis of hydrazine oxidation is an important challenge,but most electrocatalysts still suffer from low efficiency and stability. • Inspired by the relatively recognized performance of transition metal sulfides in the oxidation of hydrazine oxidation, the catalytic properties of two relatively stable iron sulfides of FeS 2 and Fe 3 S 4 were firstly investigated and compared via the density functional theory (DFT) calculations. Therein, the Fe centres were identified as the catalytic sites of all possible active locations. • Due to the different coordination numbers of iron-sulfur, the free energies of the dehydrogenation steps on FeS 2 were far less than those on Fe 3 S 4 , which led to the much better catalytic performance of FeS 2 . Accordingly, FeS 2 and Fe 3 S 4 were then prepared by a facile one-step hydrothermal strategy. • Following experimental results were in agreement with the DFT calculation ones: FeS 2 microspheres exhibited promising electrocatalytic performance in the electrocatalytic decomposition of hydrazine with a starting potential of 0.22 V vs . reversible hydrogen electrode (RHE) and peak oxidation current of 16 mA cm −2 (0.5 V vs. RHE). Meanwhile, stability and high faradaic efficiency (3.5e − /N 2 H 4 ) were obtained for hydrazine oxidation to N 2 . Inspired by the relatively recognized performance of transition metal sulfides in the oxidation of hydrazine, the catalytic properties of FeS 2 and Fe 3 S 4 are compared via the density functional theory calculations. Due to the different coordination numbers of iron-sulfur, the free energies of the dehydrogenation steps on FeS 2 are far less than those on Fe 3 S 4 , which led to the much better catalytic performance of FeS 2 . Accordingly, FeS 2 microspheres are rationally proposed as a more efficient electrocatalyst for hydrazine oxidation, which is then prepared by a facile one-step hydrothermal strategy. Such FeS 2 microspheres show great activity for hydrazine oxidation with an onset oxidation potential of 0.22 V vs . reversible hydrogen electrode, and a peak current density of 16 mA cm −2 . Meanwhile, stability and high faradaic efficiency (3.5e − /N 2 H 4 ) is obtained for hydrazine oxidation to N 2 .