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

Abstract

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 (SiP) 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/SiP 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/SiP’s potential for advancing miniaturized supercapacitors with high capacitance retention, cycle stability, and energy density.