Significant Enhancement of the Photoelectrochemical Activity of Nanoporous TiO2 for Environmental Applications

• Three-step anodization synthesis of nanoporous TiO2.
• Electrochemical reduction treatment on the formed nanoporous TiO2.
• Six times enhancement of photocurrent facilitated by the electrochemical treatment.
• High catalytic activity toward photoelectrochemical degradation of RhB.

Here we report on a significant enhancement of the photocatalytic activity of nanoporous TiO2, which was achieved via facile electrochemical reduction. Nanoporous TiO2 was directly grown using a three-step elecreochemical anodization process in ethylene glycol + 0.3 wt% NH4F + 2 wt% H2O. The formed nanoporous TiO2 was further electrochemically treated and tested as a catalyst for photoelectrochemical water splitting and the photoelectrochemical oxidation of Rhodamine B (RhB). The photocurrent of the as-prepared nanoporous TiO2 was very high, 7.70 mA cm−2 at 1.5 V; and it was significantly increased to 46.23 mA cm−2 after the further electrochemical treatment. When compared with untreated nanoporous TiO2, the facile reduction treatment resulted in a remarkable increment in the donor density of the nanoporous TiO2 by approximately four-orders of magnitude. Moreover, the treated nanoporous TiO2 exhibited six times faster photoelectrochemical degradation of RhB as well as remarkable stability. Augmented solar light and visible light catalytic activity toward the photoelectrochemical degradation of RhB were also observed. The simplicity and efficacy of the new approach described in this study makes possible the integration of nanoporous TiO2 in the design of high-performance energy harvesting and water purification technologies.

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