Enhancing bifunctional and overall water splitting electrocatalytic activity copper MOF by integrating conducting rGO

Abstract

The electrocatalytic water splitting activity of metal organic frameworks (MOFs) is optimized/enhanced by tailoring the coordination environments and fabricating composites with conducting materials. Herein, a water coordinated copper (Cu) MOF was synthesized using monosodium glutamate (MSG) and improved its bifunctional electrocatalytic activity in alkaline medium by integrating conducting rGO. Single crystal structural analysis confirmed the formation of 3D network structure with a water coordination and a lattice water molecule. Electrocatalytic studies of CuMSG showed relatively weak activity both in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It required 381 and 408 mV to achieve 20 mA/cm2 current density, respectively. However, the electrocatalytic activity of CuMSG was strongly enhanced by fabricating composite with conducting rGO. CuMSG/rGO 250 and 280 mV to produce the 20 mA/cm2 current density. The low Tafel slope of CuMSG/rGO (128 (HER) and 48 mV/dec (OER)) compared to CuMSG (170 (HER) and 75 mV/dec (OER)) indicated improved kinetics at the electrode-catalyst interface after combining with conducting rGO. The integration rGO with CuMSG also reduced the charge transfer resistance (2.86 (HER) and 3.38 Ohm (OER)), which also contributed for enhanced bifunctional electrocatalytic activity. The bifunctional electrocatalytic activity of CuMSG-rGO was utilized for overall water splitting and required the cell potential of 1.72 V to achieve the 10 mA/cm2 current density. CuMSG-rGO electrocatalyst displayed good stability over 20h in OER, HER as well as overall water splitting.