Conductive porous boron-doped polycrystalline diamond directly synthesized from graphite and aluminum diboride via high-pressure high-temperature processing

Porous self-supported boron-doped polycrystalline diamond (P-BDD) bulk electrodes were directly fabricated from graphite and aluminum diboride (AlB2) through a one-step high-pressure high-temperature (HPHT) process, without prior synthesis of BDD particles or subsequent consolidation. The resulting P-BDD exhibited a diamond-dominant crystalline structure, porous morphology, and a room-temperature electrical resistivity of 1.66 × 10−3 Ω·m. Raman spectroscopy showed features consistent with boron incorporation, while Hall measurements confirmed p-type conduction with a hole-carrier concentration of 3.18 × 1023 m−3. The electrode exhibited an electrochemical potential window of approximately 2.13 V in 0.5 M H2SO4 and maintained stable electrochemical performance during repeated cycling. In addition, the P-BDD electrode demonstrated improved thermal oxidation resistance, with an oxidation onset temperature of approximately 969°C. The electrochemical oxidation capability was evaluated using 60 mL of methylene blue solution (30 mg·L−1), achieving approximately 98% MB decolorization within 30 min under galvanostatic conditions. This work provides a direct one-step HPHT strategy for preparing porous BDD bulk electrodes with combined electrical conductivity, thermal stability, and electrochemical oxidation capability.