Customized boron-doped diamond electrodes for efficient water treatment via HF-CVD parameter optimization

Among the Design of Experiments (DoE) approaches available, the Taguchi method offers a methodical and effective way to optimize designs with fewer experimental trials. The effects of deposition conditions on the final properties of boron-doped diamond (BDD) films for water treatment applications deposited in a Hot Filament Chemical Vapor Deposition (HF-CVD) reactor were evaluated by applying a Taguchi Matrix. Methane to hydrogen (CH4/H2) ratio, argon mass flow, and total gas pressure were the controllable factors, each in three different levels. Diamond quality was affected by a combination of the three considered factors. A 0.02 CH4/H2 ratio was found as the optimal value to yield films with reduced non-diamond carbon inclusions in our CVD system. Resistivity, residual stress, double-layer capacitance, and surface roughness were mainly affected by total pressure and argon content. The methane content and the total pressure significantly influenced growth rate and grain size. The latter was primarily responsible for changes in the electrochemical potential window and the electron transfer process of the BDD films. Within the studied range of deposition conditions, the optimal deposition parameters to obtain BDD films for water treatment applications were: 0.02 CH4/H2 ratio, 25 mbar total gas pressure, and 30 sccm argon mass flow.