Visible light responsive vanadium-substituted hydroxyapatite photocatalysts

• After substitution of Ca by V ions in HAp, visible light driven photocatalytic activity appeared.
• The visible light driven photocatalytic activity was increased with V content.
• The visible light response would be owing to the generation of an acceptor level due to V ions.

Hydroxyapatite (HAp) has a potential to be an excellent photocatalyst because of its strong adsorption ability for organic substances. However, the HAp has a poor photocatalytic ability without modification. We firstly revealed that after substitution of a part of Ca ions by V ions in HAp lattice (V:HAp), visible light driven photocatalytic activity appeared. The substituted V ions were pentavalent at bivalent Ca sites, causing the introduction of amounts of Ca defects in the HAp lattice to keep electric neutrality. In spite of any amount of the Ca defects, the HAp structure of V:HAp was kept after calcination at 400 °C. Then, the photocatalytic activity was increased with V content. The visible light response of V:HAp would be owing to the generation of an acceptor level due to V ions of which the redox potential was enough negative to reduce O2 to H2O2 via two electron process.

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