Carbon nitride shielded Co–W–S interfaces for ultra-stable hydrogen evolution in harsh acidic media

Abstract

The hydrogen evolution reaction (HER) in strongly acidic media underpins proton-exchange-membrane (PEM) electrolysis, yet achieving precious-metal-free stability at industrial current densities remains a major challenge. Here, we report a carbon-nitride-armored Co–W–S heterostructure (CN@2CoS/WS₂/CP) grown on carbon paper via hydrothermal deposition followed by melamine pyrolysis. WS₂ nanosheets provide acid-resistant structural stability, CoS nanoparticles supply abundant redox-active sites, and a conformal amorphous CN overlayer enhances electronic conductivity, suppresses metal dissolution, and promotes defect formation. This integrated architecture delivers overpotentials of 154 and 176 mV at 10 and 100 mA cm⁻² in 0.5 M H₂SO₄, along with a Tafel slope of 48.5 mV dec⁻¹ and a turnover frequency of 0.168 s⁻¹, outperforming all WS₂- and CoS-based references. Electrochemical impedance and C_dl measurements (19.5 mF cm⁻²) confirm accelerated charge transfer and preserved electrochemically active surface area. Crucially, the electrode maintains continuous operation for 10 days at 500 mA cm⁻² with undetectable Co/W leaching (0.00 ppm), retaining both morphology and chemical integrity. Density-functional-theory calculations reveal near-thermoneutral hydrogen adsorption (ΔG_H ≈ −0.18 to −0.26 eV) at the Co–W–S interface and support a Volmer–Heyrovsky mechanism involving CN-stabilized H-spillover, consistent with H₂-TPR and redox diagnostics. This study demonstrates that dynamic carbon-nitride shielding is an effective and scalable strategy for constructing acid-resilient HER electrodes capable of long-term high-current operation.