Advanced Electrochemical Investigations of Hybrid sp²/sp³-Bonded Carbon Interfaces Consisting of Boron-Doped Carbon Nanowalls and Diamond Films

The integration of allotropic sp²-/sp³-bonded carbon (sp²C/sp³C) has evoked increasing attention since they offer a versatile and rich playground for carbon electronics, electrochemical sensing platforms, and optoelectronic neuromorphic computing attaining enhanced performance [1]. In this work, we synthesized lightly boron-doped carbon nanowalls/diamond (BCNW/D) interfacial architectures using microwave plasma-enhanced chemical vapor deposition on nanodiamond seeded p-Si(100) and SiO₂/p-Si(100) substrates. The hierarchical features constituted by complex morphology defined with microcrystallite diamond grains intertwined with vertically-aligned BCNW as a thin layer revealed using electron microscopy complemented with structural, electrical, and electrochemical properties such as activation energy (E_a), electron transfer rate (k_eff) and redox potential shifts (ΔE_p). The hydrogen plasma during deposition plays an effective role in the transformation of sp²C ↔ sp³C, eventually leading to various complex morphologies. While the flat band potential and hole-acceptor carrier concentration were estimated using the Mott-Schottky relationship, the fabricated hybrid carbon interfaces exhibited electroactivity toward the ferro/ferricyanide redox couple. The redox peak separation value ranged between 82-94 meV for all the samples studied and the electron transfer rate was determined using different analytical procedures. The experimental findings are ascribed to the graphitic sp²C pathway paired with the surface conductive channel of H-terminated diamond films surface for electron transportation and their robust nature. This work promotes the development of high-performance electroanalytical and photoelectrochemical platforms based on hybrid carbon interfaces and the method proposed here also provides an effective strategy to construct diamond and graphene-related nanostructures for diverse applications. The author (S.G.) acknowledges funding (Nobelium IDUB Award). [1] S. Gupta et. al., submitted (2024).