Tuning the electrochemical properties of polymeric cobalt phthalocyanines for efficient water splitting

Abstract

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.