Generation of Nanoporous Diamond Electrodes Fabricated by a Low-Cost Process at Moderate Temperatures

A unique approach to fabricate nanoporous diamond morphology using molten salt thermal etching (MSTE) at a moderate temperature (450 °C) of boron-doped ultrananocrystalline diamond (B-UNCD) electrodes is presented. The developed one-step method is simple, environmentally friendly, inexpensive, and provides nanoporous diamond electrodes with nearly unlimited Z-depths. Moreover, it is also applicable to non-conductive diamond films. The appropriate etching mechanism is attributed to the preferential etching of sp² carbon phases localized at the grain boundaries by MSTE-generated highly oxidizing species. The fabricated B-UNCD electrodes show an increase in the electrochemical active area (ECSA) of 15% after 3 h of the MSTE treatment, making them promising materials to use as sensors for electroactive species. Such nanoporous B-UNCD presents a favorable working electrode with increased sensitivity for the electrochemical detection of 4-nitrophenol. Moreover, the fabricated nanoporous B-UNCD electrode showed 49 times higher capacitance (3534 μF cm^–2) than the pristine (non-porous) B-UNCD material (71.50 μF cm^–2).