In-situ grown nickel iron bimetal organic frameworks from activated Ni foam for efficient energy storage and electrocatalysis: Study of metal ratio and nickel precursor effects

Ex-situ fabrication of electroactive electrodes encounters serious peeling off problems. Nickel foam (NF) shows promise as conductive substrate of electroactive electrodes due to high surface area, porosity and conductivity. To broaden NF applications and enhance attachments, applying in-situ growth for establishing efficient active materials on NF is necessary. In this study, nickel iron bimetal organic frameworks (NiFeMOF) are firstly synthesized from activated NF as electroactive electrodes for energy storage and electrocatalysis. Metal ratio and nickel precursor effects are studied to elucidate growing mechanism of electroactive materials. The optimal NiFeMOF/NF presents the highest specific capacitance (C_F) of 2017.9 F/g at 20 mV/s, while MOF/NF electrodes prepared with only Ni and Fe respectively show smaller C_F values of 622.1 and 1121.8 F/g. The superior electrocatalytic ability is achieved by NiFeMOF/NF. Inclusion of additional Ni salts is necessary for synthesizing Ni-MOF on NF with improved energy storage ability, but that prepared without addition of Ni salt exhibits better electrocatalytic ability. Trade-off between electrochemical surface area and electrical conductivity is proved as crucial factor in designing electroactive materials for energy storage and electrocatalytic water splitting. This study brings novel insights into establishment of effective electroactive materials for electrochemical systems using simple concepts and techniques.