Porous self-supported boron-doped polycrystalline diamond (P-BDD) bulk electrodes were directly fabricated from graphite and aluminum diboride (AlB

2

) 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 × 10

23

m

−3

. The electrode exhibited an electrochemical potential window of approximately 2.13 V in 0.5 M H

2

SO

4

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 ele

ctrochemical oxidation capability.