In these experiments the applied voltage was slightly below the inception value and therefore, no
discharge was generated. Line (2) corresponds to the corona discharge in the same solution at
the applied voltage near the sparking value. The relatively small amount of phenol degradation
is apparently caused by the oxidative action of OH radicals produced by the discharge. Line (3)
demonstrates that a significant amount of H2O2 is produced by the discharge. Through addition
of 0.5 mmol/l of FeCl2 to the solution containing phenol in distilled water, the hydrogen peroxide
was decomposed to OH radicals according to the Fenton‘s reaction