An efficient poly(5-(4-methoxyphenyl)dipyrromethane-based Mn(ii) complex modified glassy carbon electrode for photo-assisted electrocatalytic water oxidation at neutral pH

Abstract

The development of efficient, robust, stable, and inexpensive catalysts for water oxidation is one of the most challenging tasks for the scientific community. To increase the durability and long-term stability of molecular water oxidation catalysts, heterogenization of molecular catalysts on electrode surfaces has emerged as a promising approach. In this pursuit, here we report the electropolymerization of 5-(4-methoxyphenyl)dipyrromethane (mdp) and the subsequent formation of a polymeric manganese(II) complex through self-assembly on a glassy carbon electrode for the electrochemical and photo-electrochemical oxidation of water. The modified electrode was characterized using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, UV-visible spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analysis, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The newly developed electrode Mn-mdp-GCE could electrocatalyze water oxidation in the presence of white LED light efficiently (Faraday efficiency ∼83%) in a neutral pH medium. The Mn(II) polymeric complex-modified electrode could photoelectrocatalyze water oxidation at a low overpotential (η) of 306 mV at J = 1.0 mA cm⁻². The surface immobilized polymeric Mn(II) complex showed high stability during seven hours of long electrolysis, and its molecular identity was confirmed from voltammetric, spectroscopic and microscopic results.