Porphyrin-functionalized glassy carbon electrodes for electrochemical water splitting

Herein, we electrografted the free-base 5,10,15,20-tetrakis(4-aminophenyl)porphyrin, (H₂TAPP) and the cobalt-based porphyrin (CoTAPP) onto the surface of glassy carbon electrodes (GCE) which results in a H₂TPP-GCE and CoTPP-GCE polymer, respectively. Electropolymerization forms a stable, covalently bonded network, enhancing the electrochemically active surface area (to 47.7 cm², 29.2 cm², respectively) and lowering the charge transfer resistance during OER and HER based on EIS data. H₂TPP-GCE exhibits a Tafel slope of 113 mV dec^-1 for HER, while CoTPP-GCE achieves 80 mV dec^-1 for OER. The overpotentials are 511 mV (HER) and 540 mV (OER), with both electrodes remaining stable over 20 hours.