Study of electrochemical hydrogen charge/discharge properties of FePO4 for application as negative electrodes in hydrogen batteries

We report the electrochemical hydrogen charge/discharge properties of electrodes containing crystalline and amorphous FePO4 as active material in KOH electrolyte. Crystalline and amorphous FePO4 were synthesized by an alcohol-assisted precipitation method, and the powders obtained were characterized by X-ray diffraction. X-ray photoelectron spectroscopy is used to investigate the mechanism of hydrogen charge/discharge behavior of FePO4. The electrochemical hydrogen charge/discharge properties of electrodes containing crystalline and amorphous FePO4 were investigated for potential application as negative electrodes in rechargeable hydrogen batteries. In galvanostatic discharge/charge mode at 25 °C, the crystalline FePO4 showed a maximum discharge capacity of 109 mA h g−1, while the amorphous FePO4 showed a maximum discharge capacity of 81.4 mA h g−1. The electrochemical kinetic properties, exchange current density, and proton diffusivity were calculated using linear polarization measurement and the potential-step method.