The improved photoelectrocatalytic degradation of rhodamine B driven by the half-rectified square wave

•Half-rectified square wave is first applied as potential for photoelectrocatalysis.•HR-SW is much more efficient in PEC degradation of rhodamine B than direct current.•HR-SW may enhance RhB adsorption and TiO2 exciton dissociation alternately.•HR-SW of 3V, 50 Hz and 50% duty ratio is optimal for RhB PEC degradation.

The photoelectrocatalytic (PEC) degradations of rhodamine B (RhB) over titanium oxide (TiO2) thin films have been investigated under three applied potential modes of direct current (DC), square wave (SW), and half-rectified square wave (HR-SW). The synergetic effect between the light and electricity under the SW mode (~1.0) was found much lower than those under the DC (~9.0) and HR-SW (~25.9) modes, because the flow direction of the photoelectrons was periodically varied under the SW, leading to almost no improvement in the exciton dissociation. Compared to the DC mode, the HR-SW mode might offer much enhanced adsorption of RhB on the TiO2 surface and exciton dissociation in the TiO2 anode during the low and high bias potential periods, respectively, thereby giving rise to significantly improved PEC degradation of RhB. The current research provides a low-cost method to achieve the efficient PEC removal of liquid-phase organic pollutants, which is useful for advancing the photocatalytic technique toward the large-scale commercial application.

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