Bimetallic electron-induced phase transformation of CoNi LDH-GO for high oxygen evolution and supercapacitor performance

Bifunctional energy materials in energy conversion and storage have a significant research value. Herein, bifunctional α-phase Co2Ni1 layered double hydroxide (LDH)-graphene oxide (GO) was prepared through bimetallic electronic regulation and GO assistance. Without GO addition, Co2Ni1 LDH bulk is dominated by the β phase. Compared with the β-phase type, the α-phase Co2Ni1 LDH-GO shows a larger interlayer spacing, which shortens the ion movement path and time and thus improves the electrochemical performance. As an electrocatalyst for oxygen evolution in energy conversion, the ultrathin α-phase Co2Ni1 LDH-GO possesses the lowest overpotential η10 of 218.5 mV at a current density of 10 mA cm−2. It also exhibits excellent stability mainly due to the Co-O bond by the cooperative electronic regulation of Ni2+. With the increase in Co-O bond length, the adsorbed OH− further oxidizes Co3+ to Co4+. As an electrode in a three-electrode supercapacitor for energy storage, the specific capacitance of Co2Ni1 LDH-GO can reach 3317.5 F g−1. When used in an asymmetric capacitor (Co2Ni1 LDH-GO//activated carbon), Co2Ni1 LDH-GO shows a remarkable capacitance of 328.75 F g−1 and excellent cycling stability. This work provides a phase transformation approach to improve the oxygen evolution and supercapacitor performance of multifunctional materials.