Theoretical investigation of electrochemical behavior of DTPA and its interfacial synergy with defected graphene toward photocatalytic applications

A comprehensive density functional theory (DFT) investigation is performed to elucidate the electrochemical behavior of diethylenetriaminepentaacetic acid (DTPA) and its interaction with defected graphene for photocatalytic applications. The calculations reveal that DTPA adopts a folded conformation stabilized by intramolecular hydrogen bonds. Upon oxidation, the molecule undergoes progressive hydrogen-bond weakening followed by C-C bond cleavage at higher charge states, whereas reduction induces a non-linear reorganization of the hydrogen-bond network without covalent bond breaking. Protonation and deprotonation substantially narrow the HOMO-LUMO gap, enabling visible-light photoactivity. Adsorption studies on graphene show that defect engineering, particularly the Stone-Wales defect, significantly enhances binding. A photocatalytic mechanism is proposed wherein DTPA serves as the hole source for water oxidation and defected graphene as the electron sink for oxygen reduction, providing a rational foundation for molecular-carbon hybrid photocatalysts.