Achieving high capacitance from porous boron-doped diamond by tuning the surface termination

Abstract Porous boron-doped diamond (PBDD) electrode with a high potential window, excellent stability, controllable conductivity, enhanced specific area, and tunable surface termination is a promising electrode material for the candidate. The surface termination of the PBDD electrode is easily tuned by the cyclic voltammetry (CV) scanning process with a positive potential, and an oxygen-terminated (OT) surface is achieved. The OT PBDD electrode exhibits a peak specific capacitance of 20.31 mF cm−2 (38.3% increase compared with the HT PBDD electrode, at 100 mV s−1) when 2.4 V (vs. Ag/AgCl) potential is applied, and it further comes to 36.74 mF cm−2 (81.8% increase than the HT PBDD electrode, at 10 mV s−1) with a 2.7 V (vs. Ag/AgCl) polarization potential. As the polarization voltage further increases to 3.0 V (vs. Ag/AgCl) or higher, the specific capacitance decrease. The OT PBDD electrode also keeps capacitance retention of 94.8% after 6000 CV cycles at 200 mV s−1. Moreover, we built up a symmetric device using the OT PBDD as the electrode, which exhibits good electrochemical performance, such as wide potential, high energy density (15.1 Wh kg−1), and high power density (4.05 kW kg−1).