Semiconductor photocatalysts for overall water splitting into H₂ and O₂ require metal cocatalyst, such as Pt, to catalyze H₂ evolution efficiently. However, these metal cocatalysts can also catalyze hydrogen and oxygen recombination to form water. In this paper, we found that the pre-adsorbed halogen atom catalyst could inhibit the reverse reaction of water formation from H₂ and O₂ due to the decrease of adsorption energies of H₂ and O₂ on Pt. The adsorption energy decrease of H₂ and O₂ followed the order of F/Pt < Cl/Pt < I/Pt < Br/Pt. H₂-TPD results exhibited similar dependence. This inhibition was achieved via the occupation of halogen atom on the Pt surface sites, and thereby the adsorption and activation of hydrogen and oxygen molecules were decreased. The occupation difference of halogen atoms are determined by radius of halogen ions, which further leads the different activity for H₂ and O₂ recombination. By inhibition of water formation reverse reaction, the over-all water splitting over various TiO₂ photocatalysts has been achieved. Isotope experiments with D₂O and H₂¹⁸O confirmed the over-all water splitting to H₂ and O₂. This study may help scientist to develop high-efficient photocatalyst for overall water splitting.

用于将全部水分解为H ₂和O _2的半导体光催化剂需要金属助催化剂（例如Pt）才能有效地催化H _2的逸出。然而，这些金属助催化剂也可以催化氢和氧的重组以形成水。本文发现，由于H ₂和O ₂在Pt上的吸附能降低，预吸附的卤素原子催化剂可以抑制H ₂和O ₂生成水的逆反应。H ₂和O ₂的吸附能降低遵循F / Pt <Cl / Pt <I / Pt <Br / Pt的顺序。高₂-TPD结果显示出相似的依赖性。这种抑制作用是通过在Pt表面位点上占据卤素原子来实现的，因此减少了氢和氧分子的吸附和活化。卤素原子的占据差异取决于卤素离子的半径，这进一步导致了H ₂和O ₂重组的不同活性。通过抑制水形成逆反应，已经实现了在各种TiO ₂光催化剂上的全部水分解。用D ₂ O和H ₂ ¹⁸ O进行的同位素实验证实了总的水分解为H ₂和O ₂。这项研究可能有助于科学家开发用于整体水分解的高效光催化剂。