In situ transformation of iron-group ternary metal oxides nanocubes from Co/Ni-PBA for high-performance supercapacitors

Three kinds of Prussian blue analogues (Ni-Fe PBA, Co-Fe PBA, Co/Ni-Fe PBA) with similar cubic nanostructures have been synthesized simply by one-step solution-precipitation method. By utilizing simultaneous oxidative decomposition and crystal growth, iron-group metal oxides (NiO/Fe3O4, Co3O4/Fe3O4, NiO/Co3O4/Fe3O4) with porous nanocubic structures have been converted successfully in situ from precursors of PBAs. When evaluated as anode materials for supercapacitors, the mixed metal oxides with a porous cubic structure manifest high specific capacity. The specific capacitance of ternary metal oxides (NiO/Co3O4/Fe3O4) is 2.3 times that of NiO/Fe3O4 and 3.7 times that of Co3O4/Fe3O4. Besides, the ternary metal oxides exhibit high rate stability (retention up to 72% even at 20 A g−1) and long cycle performance. The improved electrochemical performance may owe to the synergistic effect of mixed-metal-oxide porous nanostructures, which accelerates electron transport and ion diffusion.