Comparative study on prussian blue analogue derived iron nickel oxide, sulfide and phosphide as electrode materials for supercapacitors

Over the past decades, although metal oxides, sulfides and phosphides have developed as materials for supercapacitors (SCs), their SCs` performance should be deeply studied. In this work, FeNi-Prussian blue analogue (FeNi-PBA) was prepared via a simple co-precipitation method and served as a sacrificial template to prepare iron nickel oxide (NiFe2O4), sulfides (FeS/NiS2) and phosphides (Fe2P/Ni2P), whose capabilities for SCs were compared, respectively. The electrochemical results confirmed that the specific capacitance of FeS/NiS2 was 490.6 F g−1 much higher than those of NiFe2O4 (86 F g−1) and Fe2P/Ni2P (174.6 F g−1) at the current density of 1 A g−1. Therefore, the FeNiSx delivered the best electrochemical properties among them, because FeS/NiS2 composed by FeS/NiS2 heterostructure with sulfur vacancies provided an intimate/compact interfacial arrangement which better synergized the polyatomic conductivity and a large number of redox-active sites to bring about excellent electrochemical performance. Furthermore, FeS/NiS2 and activated carbon (AC) were employed to fabricate an asymmetric supercapacitor (ASC), which achieved the energy density of 54.34 Wh·kg−1 and the power density of 1349.13 W·kg−1, and could power a commercial light-emitting diode light. Among FeNiOx, FeS/NiS2 and Fe2P/Ni2P, FeS/NiS2 can be a potential electrode material for SCs attributing to its heterostructure and sulfur vacancies favourable for multi-atom conductivity and numerous redox-active sites. This work evidences that metal sulfides deliver the superior SCs` performance than the corresponding metal oxides and phosphides.