In this paper, K2FeO4 cathodes were coated with tetraphenylporphyrin (TPP) to improve their stability. Analyses involving a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FT-IR) indicated that the K2FeO4 cathodes were successfully coated with the TPP overlayer. Discharge performance tests were conducted after soaking the cathodes in a 10M KOH electrolyte for 0–6h. The discharge properties of the 8wt% TPP coated K2FeO4 cathodes indicated that they were stable, and their discharge capacity increased to 160mAhg−1 from 75mAhg−1 for the uncoated electrodes after soaking in a 10M KOH electrolyte solution for 6h. In addition, adding 5wt% sodium bismuthate (NaBiO3) to the tetraphenylporphyrin coated K2FeO4 electrode can further improve its discharge performance by increasing the discharge capacity from 275mAhg−1 to 316mAhg−1.