Ruthenium ion containing N and S rich triazine based metallopolymer as a low overpotential acid stable electrocatalyst for hydrogen evolution

The rational design of under saturated redox-active metal centers distributed on the organo-polymeric surfaces has gained substantial attention in electrocatalysis. Herein, we report the ruthenium ions containing triazine-trithiolate (M-C₃N₃S₃) metallopolymers chemically coordinated to the copper substrate as a stable, low overpotential electrocatalyst for H₂ evolution in strong acidic media. The XPS analyses confirm the presence of Ru⁴⁺/Ru³⁺ and Cu²⁺/Cu¹⁺ in the metallopolymers. XPS and FTIR spectral analysis suggest the presence of disulphide linkages. A significant overpotential reduction for hydrogen evolution is observed with CuRu-C₃N₃S₃ metallopolymer of just ∼−145 to −155 mV vs RHE to attain −10 mA cm⁻² in 0.5 M H₂SO₄. The high exchange current densities and double layer capacitance could be attributed to the protonation capacity of redox-active centers and the uncoordinated ligand centers (N and S). The concerted proton-electron transfer mechanism improves the H₂ evolution. These metallopolymers show a low onset hydrogen evolution potential of just −45 mV vs RHE (i = −1 mA cm⁻²). Tafel slope values suggest the Volmer-Heyrovsky mechanism is involved in HER. The potentiostatic impedance spectral analyses indicate, CuRuTCA show the reduction in charge transfer resistance of nearly 10 and 700 times with respect to CuNiTCA and bare Cu electrodes respectively. These electrodes display an excellent long-term stability for hydrogen evolution.