Tuning the Electrochemical Properties of Polymeric Cobalt Phthalocyanines for Efficient Water Splitting

Polymeric metal phthalocyanines have great potential as electrocatalysts, yet their incorporation on a current collector without losing the activity of metal centers remains a challenge. Herein, a new strategy for preparing a series of polymeric cobalt phthalocyanines containing S linkers (pCoPc-1) or SO₂ linkers (pCoPc-2) and their tunable electrochemical properties are reported. The pCoPcs coated on various substrates show favorable electrocatalytic activities toward oxygen and hydrogen evolution reactions (OER and HER). Particularly, the pCoPc-1 layer on Co₃O₄ nanosheet arrays exerts a cooperative effect enhancing both the OER and HER performances, and the subsequent phosphorization (P@pCoPc-1/Co₃O₄|CC) significantly boosts the HER performance with enhanced hydrophilicity and conductivity. The high permeability and stability reinforcement of the pCoPc-1 layer allow the phosphorization of underlying Co₃O₄ to CoP without degradation, which remarkably enhances OER and HER performances as manifested by low overpotentials of 320 and 120 mV at 10 mA cm⁻², respectively. When engaged as a bifunctional electrocatalyst for the overall water splitting, the P@pCoPc-1/Co₃O₄|CC requires a low cell voltage of 1.672 V at 10 mA cm⁻², showing long-term durability and mechanical robustness. This study demonstrates the collaborative catalytic role of polymeric macrocyclic compounds that offers versatile tunability and stability for various electrocatalytic reactions.