Nanostructured Boron-Doped Ultra-Nanocrystalline Diamond Micro-Pyramids: Efficient Electrochemical Supercapacitors

The miniaturization of electrochemical supercapacitors (EC-SCs) requires electrode materials that are both durable and efficient. Boron-doped diamond (BDD) films are an ideal choice for EC-SC due to their durability and exceptional electrochemical performance. In this study, nanostructured boron-doped ultra-nanocrystalline diamonds (NBUNCD) are fabricated on Si micro-pyramids (Si_P) using a simple reactive ion etching (RIE) process. During the etching process, the high aspect ratio and the induction of sp² graphite in these nanorod electrodes achieved a maximum specific capacitance of 53.7 mF cm^-2 at a current density of 2.54 mA cm^-2, with a 95.5% retention after 5000 cycles. Additionally, the energy density reached 54.06 µW h cm^-2 at a power density of 0.25 µW cm^-2. A symmetric pouch cell using NBUNCD/Si_P exhibited a specific capacitance of 0.23 mF cm^-2 at 20 µA cm^-2, an energy density of 31.98 µW h cm^-2, and a power density of 0.91 µW cm^-2. These superior EC properties highlight NBUNCD/Si_P's potential for advancing miniaturized supercapacitors with high capacitance retention, cycle stability, and energy density.