Boron-doped diamond-coated graphite electrodes with 3D interdigital structure for high current and narrow potential window

The application of a boron-doped diamond (BDD) coating to mechanical pencil leads enabled the fabrication of scalable three-dimensional interdigital electrodes that combine the high current density of graphite with the corrosion resistance of diamond. After 12 hours of cyclic voltammetry (CV) in 1 M NaOH, the CV traces of the BDD electrodes overlapped completely. The anodic and cathodic peak current densities were +6.7 × 10⁻⁴ A/cm² and −5.9 × 10⁻⁴ A/cm², respectively. These values were approximately twice those of platinum (Pt) and only ~35% lower than those of a non-coated graphite electrode. Despite this high reactivity, the potential window of the BDD electrode was narrower than previously reported ( ΔE = 1.88 V; Pt = 2.00 V), which can be attributed to the synergistic effects of surface oxidation, heavy boron doping, and minimized iR drops that suppress side reactions. Tafel analysis indicated the fastest interfacial rate ( i₀ = 8.34 × 10⁻⁵ A/cm², α ≈ 0.59), confirming highly symmetric charge transfer in both anodic and cathodic directions. Post-CV scanning electron microscopy (SEM) revealed no cracks or delamination, while Raman spectroscopy confirmed the stability of the diamond peak at 1332 cm -1 , verifying both structural and chemical robustness under strongly alkaline conditions. Due to the combination of high exchange current density and a deliberately narrow potential window, the three-dimensional BDD/graphite composite electrode is expected to be both durable and efficient. It offers promise as a long-life electrode material for alkaline fuel cells and other high-current electrochemical devices, providing a cost-effective alternative to platinum.