Influence of pore size of Ti substrate on structural and capacitive properties of Ti/boron doped diamond electrode

Abstract

This work is aimed at understanding the influence of pore size of titanium (Ti) substrate on the capacitive properties of boron doped diamond (BDD) electrode. BDD films were deposited on Ti substrates with five different pore sizes - 2.5, 5.0, 20.0, 30.0, 50.0 μm - using hot filament chemical vapor deposition (HFCVD). The pore size of substrate was found to cause significant variations in surface structure and capacitive properties of the Ti/BDD electrodes. The optimum pore size that resulted in best surface structure and capacitive properties was found to be 30.0 μm. The Ti30.0/BDD electrode was found to possess higher sp2-C bonds content, sp3-C bond with doped boron atom, more closely interlaced grains and bigger specific surface area than other electrodes. The maximum capacitance obtained for Ti30.0/BDD electrode was 53.3 mF cm−2, with minimum impedance value Rct of 4.8 Ω. The minimum capacitance of 1.07 mF cm−2 was obtained for the Ti50/BDD electrode, and the maximum impedance value Rct of 290 Ω was obtained by the Ti20.0/BDD electrode. Furthermore, the Ti30/BDD electrode possessed a favorable electrochemical stability of capacitance retention of 89.3% after 2070 cycles. A mechanism by which pore size affects the capacitance properties of the Ti/BDD electrode is proposed and discussed in this paper.