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

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.