Enhanced Photocatalytic H₂-Production Activity of TiO₂ by Ni(OH)₂ Cluster Modification

Ni(OH) 2 cluster-modified TiO 2 (Ni(OH) 2 /TiO 2 ) nanocomposite photocatalysts were fabricated by a simple precipitation method using Degussa P25 TiO 2 powder (P25) as support and Ni(NO 3 ) 2 as precursor. The effect of Ni(OH) 2 cluster loading content on the photocatalytic hydrogen production rates of the as-prepared samples in methanol aqueous solution was investigated. The results showed that the photocatalytic H 2 -production activity of TiO 2 was significantly enhanced by loading Ni(OH) 2 clusters. The optimal Ni(OH) 2 loading content was found to be 0.23 mol %, giving a H 2 -production rate of 3056 μmol h −1 g −1 with quantum efficiency (QE) of 12.4%, exceeding that on pure TiO 2 by more than 223 times. This high photocatalytic H 2 -production activity is due to the deposition of Ni(OH) 2 clusters on the surface of TiO 2 . The enhanced mechanism is because the potential of Ni 2+ /Ni (Ni 2+ + 2e − = Ni, E o = −0.23 V) is slightly lower than conduction band (CB) (−0.26 V) of anatase TiO 2, meanwhile higher than the reduction potential of H + /H 2 (2H + + 2e − = H 2, E o = −0.00 V), which favors the electron transfer from CB of TiO 2 to Ni(OH) 2 and the reduction of partial Ni 2+ to Ni 0 . The function of Ni 0 is to help the charge separation and to act as cocatalyst for water reduction, thus enhancing the photocatalytic H 2 -production activity.