Facile soft solution synthesis of delafossite structured Cu(Cr1-xFex)O2 (x=0, 0.5, and 1) materials and their supercapacitor application

The investigation of metal oxides with delafossite-type crystal structure for electrochemical energy storage applications is an emerging area. Interestingly, the ternary oxides Cu(Cr1-xFex)O-2 (0 <= x <= 1) with delafossite-type layered crystal structure are promising transparent p-type semiconductor and thermoelectric materials with excellent potential for electrochemical applications. However, the synthesis of single-phase Cu(Cr1-xFex)O-2 (0 <= x <= 1) is challenging due to the limited stability of Cu+ oxidation state in ambient condition. In the present study, we have successfully synthesized polycrystalline Cu(Cr1-xFex)O-2 (x = 0, 0.5, and 1) using a new polymer complex gel technique. The polymer complex gel method can produce homogeneous metal oxide with multiple cations. This is because the metal ions are very near (< few nm) to each other in the precursor. Furthermore, the solid solutions Cu(Cr1-xFex)O-2 (x = 0, 0.5, and 1) have been synthesized successfully for the first time using this solution processing technique. Typically, a homogeneous solution containing stoichiometric metal ions and tartaric acid forms a gel-like substance upon evaporation. This gel is dried and followed by calcination at 900 degrees C in N-2 atmosphere to prepare polycrystalline powder of Cu(Cr1-xFex)O-2 (x = 0, 0.5, and 1). The crystal structure and phase purity of all the samples were confirmed by powder X-ray diffraction (PXRD) technique. The as-prepared CuCr0.5Fe0.5O2 electrode delivered excellent specific capacitance (Csp) and demonstrated notable electrochemical stability in galvanostatic charge-discharge (GCD) cycling, which may indicate enhancement of electrochemical performance of supercapacitor electrode materials due to synergistic effect of multiple metal ions. In conclusion, we have explored a new synthesis method and investigated electrochemical properties of new material with novel crystal structure and excellent potential for electrochemical supercapacitor applications.