Synthesis and Low‐Temperature Capacitive Performances of Ternary Active Site CoNiFe Hydroxides

CoNiFe ternary hydroxides were synthesized via hydrothermal method and the synthesis conditions (temperature, reaction time and Co/Ni/Fe molar ratio) were investigated. High temperature and long reaction time help to increase the crystallinity of the as‐prepared materials yet result in creating the impurities (Co(OH)2, Ni(OH)2 and Fe3O4) in addition to layered double hydroxide (LDH). Pure ternary CoNiFe LDH phase is obtained at the optimized condition at 130 °C for 12 h when Co/Ni molar ratios are 3:1 and 1:1. Cyclic voltammetry and galvanostatic charge/discharge tests display the capacitive performances at −20 °C of the ternary LDH material with Co/Ni molar ratio of 3:1 is superior to binary CoFe LDH. The synthesis of trinary active site CoNiFe layered double hydroxide via hydrothermal reaction is heavily influenced by temperature, reaction time and Co/Ni molar ratio. The optimal synthetic condition is at 130 °C for 12 h in order to obtain pure CoNiFe LDH. It delivers almost six times capacitance of binary CoFe LDH in 6 M KOH at −20 °C.