Enhanced photocatalytic mechanism of the Nd-Er co-doped tetragonal BiVO4 photocatalysts

- The Nd3+/Er3+ co-doping with significant lattice distortion can induce impurity energy levels in BiVO4 to trap electrons, improving the carrier separation efficiency.
- The energy transfer occurs between the Er3+ and Nd3+ of co-doped BiVO4, exhibiting much higher up-conversion light response.
- Nd3+/Er3+ co-doped BiVO4 obtains a tetragonal phase with lattice distortions and leads to more positive VB potentials.

The Nd/Er co-doped tetragonal BiVO4 photocatalysts are synthesized by a microwave hydrothermal method, and the crystal structures, morphologies and optical properties are characterized. The substitution of Nd3+ and Er3+ for Bi3+ sites leads to distortion of the [VO4] tetrahedron chains and induces the monoclinic structure transforming into the tetragonal structure, with the morphology evolving from nano particle agglomerations to disorganized regular rods agglomerations. The impurity energy levels induced by Nd3+ and Er3+ in the energy band of BiVO4 act as electron traps and have further energy transfer in the up-conversion processes to facilitate the photocarriers' separation. The more positive VB positions in the co-doped BiVO4 band structures can also effectively enhance oxidation capacity. Based on the above synergetic effect, the degradation rate the degradation rate of co-doped tetragonal BiVO4 photocatalyst can reach the highest 96% within 150 min under simulated sunlight and 20 min under the NIR irradiation.

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