Unlocking the full electrochemical potential of diamond-like carbon (DLC) thin films hinges on a nuanced understanding of their synthesis parameters. This study meticulously investigates the profound influence of the methane-to-hydrogen (CH₄/H₂) gas ratio on the electrochemical performance of DLC films, precisely fabricated on titanium substrates via direct current plasma-enhanced chemical vapor deposition (DCPECVD). A systematic exploration across CH₄/H₂ ratios from 0.5/30 to 4.5/30 sccm revealed a dramatic impact on the film's microstructure, particularly its sp³/sp² hybridization ratio and grain morphology. Comprehensive microstructural characterization was performed using scanning electron microscopy (SEM) and Raman spectroscopy, while electrochemical behavior was quantitatively assessed via electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis. The findings unequivocally establish a direct correlation between the CH₄/H₂ ratio and both the structural attributes and electrochemical efficacy of the DLC coatings. Strikingly, an optimized CH₄/H₂ ratio of 0.5/30 sccm yielded DLC films with a superior microstructure, marked by a higher sp³/sp² ratio and finely uniform grain structures, which, in turn, facilitated markedly enhanced electrocatalytic activity. Furthermore, a consistent n-type semiconductor conductivity was observed across all investigated DLC samples.