Imine linked Cu^II-metallopolymer: A sustainable Electrocatalyst for hydrogen production

Despite extensive efforts, only limited breakthroughs have been made in developing low-cost, efficient, and durable electrocatalysts. In this context, coordination polymers have emerged as promising sustainable catalysts, offering low overpotentials and high durability for electrocatalytic applications related to energy and environmental challenges. In this work, a parqueted two-dimensional (2D) polymeric chain, [C₁₈H₁₆CuF₂N₂O₂]_n (Cu-polymer), has been constructed by using fluorinated Schiff base [N,N′-bis (5-fluoro-salicylidene)-butanediamine] (H₂L) ligand by a facile, simple, slow evaporation route. Its formation is validated by UV, FTIR, and single-crystal X-ray diffraction (SCXRD). Cu-polymer crystallizes in a monoclinic system with the C2/c space group, forming polymeric chains composed of alternating Cu₂O₂ and Cu₂N₄C₈ rectangular grid layers. XPS analyses show that the Cu center is in +2 oxidation state. TGA outcomes indicate that the Cu-polymer is thermally stable up to ∼317 °C. Cu-polymer displays better HER performance, achieving a current density of 10 mA cm⁻² at an overpotential of 528 mV with a low Tafel slope of 267 mV dec⁻¹ in 0.25 M acetate buffer. It exhibits a high electrochemically active surface area (0.35 cm²), low charge-transfer resistance, and a turnover frequency of 2.17 s⁻¹ per Cu site at 550 mV overpotential. Additionally, the catalyst shows strong durability, maintaining its activity over 12 h with only a 5.3 % loss in current density, highlighting its robustness for hydrogen production.