Synthesis of yellow mesoporous Ni-doped TiO₂ with enhanced photoelectrochemical performance under visible light

A novel ordered mesoporous Ni-doped TiO₂ was successfully prepared via an in situ sol-gel method. TEM and SEM images showed that the synthesized material had a highly ordered and uniform mesoporous structure. EDS and XPS confirmed that the nickel element was doped into the TiO₂ crystal lattice homogeneously in the form of Ni²⁺ ions. Meanwhile, the doping of Ni changed the positions of the energy bands of TiO₂, resulting in the decrease of the band gap, and enhanced the absorption of visible light. Moreover, due to the defect sites induced by doping which could cause recombination of electrons and holes, different doping amounts were investigated in order to achieve optimized parameters. As a result, when the molar ratio of Ni/Ti was 0.01, the ordered mesoporous Ni-doped TiO₂ exhibited the highest photocurrent density of 3.1 μA cm^-2 at 1.3 V (vs. RHE) under visible light irradiation.