Efficient electrolytic hydrogen evolution from cobalt porphyrin covalently functionalized with chain-like phosphazene...

The development of efficient electrocatalysts for the hydrogen evolution reaction (HER) is crucial for advancing electrochemical water splitting technology. Herein, we report a novel hybrid electrocatalyst, CoTHPP-PDCP@DWCNTs, synthesized through a covalent functionalization of cobalt-porphyrin (CoTHPP) with chain-like polydichlorophosphazenes (PDCP) and subsequent incorporation onto double-walled carbon nanotubes (DWCNTs). The successful synthesis was confirmed by various spectroscopic techniques, which collectively revealed strong electronic interactions between components, improved charge transfer, and enhanced electrochemical stability. Notably, CoTHPP-PDCP@DWCNTs exhibited excellent HER activity, achieving low overpotentials of 159 mV in 1.0 M KOH and 102 mV in 0.5 M H₂SO₄ at a current density of 10 mA cm^-2, outperforming its precursors and many previously reported non-noble metal electrocatalysts. The enhanced HER performance can be attributed to the synergistic interactions between CoTHPP, PDCP, and DWCNTs, which increased the density of active sites, improved conductivity, and efficient charge transfer. This study highlights the importance of covalent linkage and structural engineering in optimizing HER electrocatalysts, providing insights for designing next-generation high-performance and durable non-noble metal-based electrocatalytic systems.