Pyrite FeS2/C nanoparticles as an efficient bi-functional catalyst for overall water splitting

Abstract

Exploration and fabrication of low-cost but highly active electrocatalysts, alternatives to noble metals, have remained a challenge for overall water splitting reaction. To date, few studies have reported that the Earth-abundant pyrite FeS₂ is catalytically active for hydrogen evolution reaction, while there is no study on the oxygen evolution reaction and overall water splitting reaction using pyrite FeS₂ as an electrocatalyst. Here, we offer a facile hydrothermal approach for the synthesis of FeS₂ nanoparticles by the reduction of FeCl₃·6H₂O with C₅H₁₀NS₂Na·3H₂O. The FeS₂/C nanoparticles on Ni foam (NF) deliver 10 mA cm⁻² at an overpotential of 240 mV towards the oxygen evolution reaction, which is lower than that of IrO₂. It requires 202 mV to drive the hydrogen evolution reaction to reach 10 mA cm⁻², while long-term durability and faster charge-transfer kinetics confirm the good hydrogen evolution reaction performance on FeS₂/C/Ni foam. Moreover, the pyrite FeS₂/C/nanoparticles on Ni foam are assembled as an anode and cathode in a two-electrode alkaline electrolyzer and show good overall water splitting efficiency with 1.72 V at 10 mA cm⁻².