Crystallization of FeOOH via iron salts: an anion-chemoaffinity controlled hydrolysis toward high performance inorganic pseudocapacitor materials

In this work, we designed a simple hydrolysis reaction to study the chemical roles of anions with different chemoaffinity abilities to iron ions on the crystallization of FeOOH. FeOOH products with different morphologies and sizes can be crystallized by using commercial iron salts such as FeSO4, FeCl2, FeCl3 and Fe(NO3)3. Their crystallization mechanisms can be evidenced in terms of hard–soft acid–base theory, which can control the chemical reaction and crystallization process. Herein, FeOOH particles with high electroactivity were successfully synthesized at 80 °C via the use of a single-source of iron salt in each corresponding experiment without adding any other reagents. The as-obtained FeOOH samples exhibit high specific capacitances of 441.2, 385.7, 577.3 and 619.6 F g−1, which show good potential to be candidates as high performance electrode materials for supercapacitors. Moreover, this facile synthesis method provides a huge opportunity for future practical applications of supercapacitors.