In recent years, the search on fabrication of highly efficient, stable, and cost-effective alternative to Pt for the hydrogen evolution reaction (HER) has led to the development of new catalysts. In this study, we investigated the electrocatalytic HER activity of the Toray carbon substrate by creating defect sites in its graphitic layer through ultrasonication and anodization process. A series of Toray carbon substrates with active sites are prepared by modifying its surface through ultrasonication, anodization, and ultrasonication followed by anodization procedures at different time periods. The anodization process significantly enhances the surface wettability, consequently resulting in a substantial increase in proton flux at the reaction sites. As an implication, the overpotential for HER is notably reduced for the Toray carbon (TC-3U-10A), subjected to 3 min of ultrasonification followed by 10 min of anodization, which exhibits a significantly lower Tafel slope value of 60 mV/dec. Furthermore, the reactivity of the anodized surface for HER is significantly elevated, especially at higher concentrations of sulfuric acid, owing to the enhanced wettability of the substrate. The lowest Tafel slope value recorded in this study stands at 60 mV/dec underscoring the substantial improvements achieved in catalytic efficiency of the defect-rich carbon materials. These findings hold promise for the advancement of electrocatalytic applications of carbon materials and may have significant implications for various technological and industrial processes.

Electrochemical surface modification of carbon: a highly active metal-free electrocatalyst for hydrogen evolution reaction
    Abstract
    1 Introduction
    2 Experimental section
        2.1 Materials
        2.2 Preparation of modified Toray carbon
        2.3 Characterizations
    3 Results and discussion
        3.1 Surface characterization: optical microscopy
        3.2 Wettability of the electrode
        3.3 Raman spectroscopy
        3.4 Thermogravimetric analysis
        3.5 Scanning electron microscopy and energy-dispersive X-ray analysis
        3.6 X-ray photoelectron spectroscopy
        3.7 Electrochemical studies
    4 Conclusion
    Acknowledgements 
    References

• Bhavani Kalaidhasan(Electrochemical Process Engineering Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 003, India)
• Lavanya Murugan(Electrochemical Process Engineering Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 003, India)
• C. Jeyabharathi(Electroplating and Electrometallurgy Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 003, India, Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India)
• R. Malini(Electrochemical Process Engineering Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 003, India, Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India)
• S. Vengatesan(Electrochemical Process Engineering Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 003, India, Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India)
• S. Vasudevan(Electrochemical Process Engineering Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 003, India, Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India)
• S. Ravichandran(Electrochemical Process Engineering Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 003, India, Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201 002, India) Corresponding author