A suspension containing MWCNT in DMF (3.16 mg g -1 ) was sonicated for 10 min, subsequently this ink was diluted 25% by adding 0.4 mM CoPL in DMF to achieve 2.37 mg MWCNT g -1 and 0.1 mM CoPL. This ink was further sonicated for 10 min and then dropcasted on a defined area (masked with Teflon tape) of carbon paper (0.1 mL cm -2 ), followed by drying overnight at room temperature. The electrode was then taped to a metal rod using a copper tape and the metal rod and copper tape was wrapped with Parafilm.