All in One: Contributions of Ni Dopants and Ni/NiS Dual Cocatalysts to the Enhanced Efficiency of TiO₂ Photocatalyst for the Degradation of Organic Pollutants

Inefficient solar-light absorption and rapid charge recombination have remained as the two challenges to improve the photocatalytic activity of titanium dioxide (TiO2) materials. Doping and the use of a cocatalyst are the two most investigated strategies to overcome these challenges in recent decades. However, these materials still suffer from inefficiency because of the poor distribution of dopants and cocatalysts. Herein, we report the synthesis of Ni-doped TiO2 with a Ni/NiS dual cocatalyst by using a water-soluble titanium complex as a precursor. The material exhibits a homogeneous distribution of both Ni as a dopant in the TiO2 lattice and Ni/NiS as a dual cocatalyst on the TiO2 surface. Ni dopants are found to enhance light absorption and tune the anatase/rutile phase formation. Ni/NiS dual cocatalysts play a significant role in enhancing the generation of electron–hole pairs through the formation of Ni–S–O–Ti bonds. Consequently, this material exhibits higher activity than conventional TiO2 and P25 materials in the photocatalytic degradation of methanol as an organic pollutant. Interestingly, this is the first time that a homogeneous Ni/NiS dual cocatalyst is formed simultaneously. Our results indicate that the homogeneous distribution of dopants and cocatalysts has a significant impact on the photocatalytic activity of TiO2.