The long-term photocatalytic stability of Co 2+-modified P25-TiO 2 powders for the H 2 production from aqueous ethanol solution

Abstract

In this paper, the long-term stability of photocatalytic activity of Co 2+ doped P25-TiO 2 nanoparticles for hydrogen production from aqueous ethanol solution is discussed using a photoelectrochemical method in detail. It was found that after a long-term photoreaction, the photocatalytic activity of Co 2+ ion modified P25-TiO 2 photocatalyst for hydrogen production has decreased by a factor of ca. 50%, and still was very high compared to that of pure P25-TiO 2 photocatalyst. And the steady anodic photocurrent appeared to have an obvious decrease after photoreaction (from 2.75 × 10 −4 to 1.5 × 10 −4 A), but the character of photocurrent response was still similar to photoreaction before. Moreover, the most important reason for the decrease of photocatalytic activity is the removal of CoO x active species ( x > 1) from the surface of TiO 2 photocatalyst after a long-term photoreaction. In addition, a new CoO x intermediate species ( x < 1, photooxidative potential at −0.36 V versus SCE) emerged on the surface of TiO 2 photocatalyst during photoreaction.