Effect of boron doping levels on the microstructure and characteristics of high-quality boron-doped diamond electrodes prepared by MPCVD

In order to fully understand the relationship between boron doping level and material characteristics, a series of high-quality boron-doped diamond (BDD) electrodes with different boron doping levels (B/C ratios = 1000–5000 ppm) were prepared on a silicon substrate using a self-designed microwave plasma chemical vapor deposition (MPCVD) reactor in this study. The relationship between surface morphology, structural composition, chemical bonding state, electrical conductivity and electrochemical properties of BDD electrodes was investigated systematically. With the increase of boron doping level, the grain size of the BDD electrode tends to decrease, the crystal orientation tends to be dominated by (111) orientation, the conductivity increases sharply and then gradually stabilizes, while the width of the potential window tends to decrease (4.39 V to 3.95 V from 1000 ppm to 5000 ppm), and the reversibility and stability of the electrode improves significantly. In addition, such high-quality BDD electrodes also exhibit a higher sensitivity (0.1176 μAμM−1 cm−2) and lower limit of detection (0.276 μM) in the detection of dopamine. The boron doping level in BDD electrodes plays a prominent role in material characteristics such as surface morphology, structural composition, chemical bonding state, electrical conductivity and electrochemical properties. Despite the challenging synthesis of pure sp3 carbon materials at high boron doping levels, the BDD electrodes prepared in this study exhibit high quality without sp2 defects even with high boron doping levels, and possess extremely low resistivity (~10−3 Ω·cm) and a wide electrochemical potential window (~4 V), which has not been achieved in other previous research works and offer great potential in the electrochemical applications of BDD electrodes.