Electrocatalytic HER Activity by Mono Terpyridyl Copper Complex in Homogeneous Aqueous Medium and After...

The present work describes electrochemical proton reduction by a mononuclear Cu(II) complex of formula [CuL] (where L = 4'-(4-fluorophenyl)-2,2':6',2″-terpyridine). Single crystal X ray diffraction exhibited the CuN₃O₂ core structure of the metal complex with a hydroxide and a perchlorate ancillary ligand connected to the copper center forming a square pyramidal geometry. The complex exudes a moderately high TON_HER/TOF_HER of 22 and ~205 s^-1 by peak current method with a moderate F.E of ~52%. The TON_HER/TOF_HER of the immobilized electrocatalysts on glassy carbon (GC) as (GO+1) [GO = Graphene oxide] and (GO + 1 + Nafion) was calculated to be 1.09 × 10⁶/304 s^-1 and 3.12 × 10⁶/868 s^-1 with a F.E of 86% and 93% respectively. A ligand-based electrochemical hydrogen evolution reaction (HER) was observed. The catalytic cycle was proposed after analyzing the intermediates through mass spectroscopy and density function theory. The heterogeneized electrocatalysts were drop casted on GC electrode using water and with or without Nafion. A overpotential of 407 mV and 514 mV at an onset potential of -0.55 V and -0.65 V versus normal hydrogen electrode (NHE) was observed for HER. Gas analysis was done after CPE at -1.6 V versus NHE for 3600 s through gas chromatography.