Copper coordination polymer electrocatalyst for strong hydrogen evolution reaction activity in neutral medium: influence of coordination environment and network structure

Earth-abundant, efficient electrocatalysts for the water splitting process, as a sustainable green energy source, are in high demand for addressing energy and environmental issues. Coordination polymers (CPs) are promising candidates for various applications, including catalysis and energy storage, and their tailorable architecture provides the opportunity to realize enhanced performance. Herein, we report the synthesis of copper-pyridinedicarboxylic acid (Cu-PDA) based CPs and complexes with different structural motifs and their structure-controlled, highly stable, enhanced hydrogen evolution reaction (HER) in neutral and alkaline medium. Cu-PDA CPs with water coordination and H-bonding functionality displayed superior HER activity (j(max) = 85 to 105 mA cm(-2)) compared to non-water-coordinated CPs and water-coordinated complexes. Importantly, water-coordinated Cu PDA-3 CPs required a low overpotential (eta = 290 mV) to achieve a geometric current density of 10 mA cm(-2) in neutral medium. The durability studies indicate that the catalyst is stable for 24 h without significant loss of activity. Impedance studies further support the higher activity of the water-coordinated and H-bonded functional network structure. According to our knowledge, this is the lowest overpotential reported for pure CP electrocatalysts in neutral medium without requiring complementary conducting materials.