Copper coordination polymer for multifunctional energy applications: hydrogen release, supercapacitor, and oxygen...

The development of multifunctional materials for integrated energy conversion and storage is a critical challenge for sustainable energy solutions. A copper-based coordination polymer (Cu-BTEB) was synthesized by a reflux method using 4,4',4″-(benzene-1,3,5-triyl)tris(ethyne-2,1-diyl)tribenzoic acid (H₃BTEB) as the organic linker. The catalytic efficiency of Cu-BTEB for hydrogen production by NaBH₄ hydrolysis exhibited a marked dependence on reactant concentration and temperature. Kinetic analyses demonstrated an activation energy of 72 kJ mol^-1, whereas thermodynamic factors suggested that the process is advantageous at elevated temperatures. An HGR of 6623 mL H₂ g^-1 min^-1 was observed at 25 °C using 1 mg of catalyst. The catalyst exhibited exceptional recyclability across five cycles. Electrochemical analyses revealed outstanding supercapacitor performance, displaying a specific capacitance of 290 F g^-1 at 1 A g^-1. Research on charge storage demonstrated a predominant pseudocapacitive behavior, with capacitive contributions rising from 58% to 95% as the scan rate increased. The electrode exhibited remarkable durability, maintaining about 100% of its capacitance after 5000 cycles. In the oxygen evolution reaction (OER), Cu-BTEB demonstrated a low overpotential of 270 mV at 10 mA cm^-2, a Tafel slope of 124 mV dec^-1, and a turnover frequency (TOF) of 0.09 mol O₂ s^-1, indicating favorable kinetics and high intrinsic catalytic activity.