Efficient photoelectrochemical oxidation of rhodamine B on metal electrodes without photocatalyst or supporting electrolyte

Abstract

•The efficient PEC degradation of RhB is realized using no photocatalyst.

•The efficient PEC degradation of RhB features the low salinity.

•The PEC degradation of RhB takes place on the anode and cathode simultaneously.

We designed photoelectrochemical cells to achieve efficient oxidation of rhodamine B (RhB) without the need for photocatalyst or supporting electrolyte. RhB, the metal anode/cathode, and O₂ formed an energy-relay structure, enabling the efficient formation of O₂₋ species under ultraviolet illumination. In a single-compartment cell (S cell) containing a titanium (Ti) anode, Ti cathode, and 10 mg·mL⁻¹ RhB in water, the zero-order rate constant of the photoelectrochemical oxidation (k_PEC) of RhB was 0.049 mg·L⁻¹·min⁻¹, while those of the photochemical and electrochemical oxidations of RhB were nearly zero. k_PEC remained almost the same when 0.5 mol·L⁻¹ Na₂SO₄ was included in the reactive solution, regardless of the increase in the photocurrent of the S cell. The k_PEC of the illuminated anode compartment in the two-compartment cell, including a Ti anode, Ti cathode, and 10 mg·mL⁻¹ RhB in water, was higher than that of the S cell. These results support a simple, eco-friendly, and energy-saving method to realize the efficient degradation of RhB.

Graphical abstract

Keywords

Energy relay structure / Energy saving / Photocatalyst-free and low-salinity degradation / Photoelectrochemical cell

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