We have succeeded to prepare Au nanopareticle deposited TiO₂ photocatalysts (Au/TiO₂) with control of Au nanoparticle size to be around 8 nm and variation of number density using a colloid photodepostion method. The prepared Au/TiO₂ exhibits activity on decomposition (oxidation) of formic acid by thermally activated and photo-activated catalytic reactions. The thermally activated catalytic decomposition gradually increases with increasing the number density of deposited Au NPs and saturated, suggesting that the decomposition occurs on Au NPs surface and/or near the interface of TiO₂ and Au NPs. On the other hand, the photocatalytic decomposition is significantly improved with rather small number density deposition of Au NPs and disappeared with high number density deposition.

ESR measurements of Au/TiO₂ in the surrounding similar to the photocatalytic decomposition suggests that electrons excited by plasmon resonance absorption in the Au NPs transfer to TiO₂ to promote the decomposition. However, high number density deposition enhances electron capture by neighboring Au NPs and reduces the photocatalytic activity. Thus there should be the optimum number density of Au NPs on TiO₂ for photocatalytic decomposition of formic acid.

我们已经成功地制备了Au纳米颗粒沉积的TiO ₂光催化剂（Au / TiO ₂），并利用胶体光变性方法将Au纳米颗粒的尺寸控制在8 nm左右，并且改变了数密度。所制备的Au / TiO ₂通过热活化和光活化催化反应对甲酸的分解（氧化）表现出活性。随着沉积的Au NPs数量密度的增加和饱和，热活化催化分解逐渐增加，这表明该分解发生在Au NPs表面和/或靠近TiO ₂的界面上和金纳米颗粒。另一方面，Au NP的数量密度较小时，光催化分解得到显着改善，而数量密度较高的沉积时，光催化分解消失。

与光催化分解相似，周围Au / TiO _2的ESR测量表明，在Au NPs中由等离振子共振吸收激发的电子转移到TiO _2上以促进分解。但是，高密度沉积增加了相邻Au Au NPs的电子捕获并降低了光催化活性。因此，在TiO ₂上应该有最优的Au NPs数量密度，以实现甲酸的光催化分解。