The paper reviews recent progress in enhancing the photocatalytic hydrogen production efficiency of titanium dioxide (TiO₂) through various ion-modification techniques, with a focus on metal doping. TiO₂, due to its non-toxicity, affordability, and superior photocatalytic activity, has been widely studied as a semiconductor photocatalyst for water splitting. However, its wide bandgap and rapid recombination of photogenerated carriers limit its solar energy conversion efficiency. To address these issues, researchers have explored various modification strategies, including metal doping, metal nanoparticle (NP) deposition, and non-metal doping. 1. **Metal Doping**: Metal doping introduces discrete energy states within the bandgap of TiO₂, enhancing its visible light photocatalytic activity. Transition metals like Cu, Fe, and Cr, and main group metals like Sn, Mg, Al, Zn, and Sr, have been used to reduce the bandgap and improve charge carrier separation. Noble metals such as Ag, Au, Pd, and Pt are also effective, extending the light absorption range to visible light and enhancing hydrogen evolution rates. 2. **Metal NP Deposition**: Metal NPs, particularly Au and Ag, can serve as co-catalysts or sensitizers, facilitating electron injection into the conduction band of TiO₂ via localized surface plasmon resonance (LSPR). This enhances the separation and transfer of photogenerated charge carriers, leading to improved photocatalytic performance. The size and shape of NPs significantly affect their LSPR properties, which in turn influence the photocatalytic efficiency. 3. **Non-Metal Doping**: Incorporating non-metal ions can tailor TiO₂ to better absorb visible light and improve the separation and transfer of photogenerated carriers. Various anions have been explored for their potential to enhance the photocatalytic capabilities of TiO₂. The review aims to provide a comprehensive overview of the latest advancements in ion-modified TiO₂ photocatalysts, highlighting the strategies employed and their effects on photocatalytic hydrogen production. The findings contribute to the development of advanced TiO₂-based photocatalysts for efficient water-splitting applications, addressing the challenges of energy scarcity and environmental degradation.The paper reviews recent progress in enhancing the photocatalytic hydrogen production efficiency of titanium dioxide (TiO₂) through various ion-modification techniques, with a focus on metal doping. TiO₂, due to its non-toxicity, affordability, and superior photocatalytic activity, has been widely studied as a semiconductor photocatalyst for water splitting. However, its wide bandgap and rapid recombination of photogenerated carriers limit its solar energy conversion efficiency. To address these issues, researchers have explored various modification strategies, including metal doping, metal nanoparticle (NP) deposition, and non-metal doping. 1. **Metal Doping**: Metal doping introduces discrete energy states within the bandgap of TiO₂, enhancing its visible light photocatalytic activity. Transition metals like Cu, Fe, and Cr, and main group metals like Sn, Mg, Al, Zn, and Sr, have been used to reduce the bandgap and improve charge carrier separation. Noble metals such as Ag, Au, Pd, and Pt are also effective, extending the light absorption range to visible light and enhancing hydrogen evolution rates. 2. **Metal NP Deposition**: Metal NPs, particularly Au and Ag, can serve as co-catalysts or sensitizers, facilitating electron injection into the conduction band of TiO₂ via localized surface plasmon resonance (LSPR). This enhances the separation and transfer of photogenerated charge carriers, leading to improved photocatalytic performance. The size and shape of NPs significantly affect their LSPR properties, which in turn influence the photocatalytic efficiency. 3. **Non-Metal Doping**: Incorporating non-metal ions can tailor TiO₂ to better absorb visible light and improve the separation and transfer of photogenerated carriers. Various anions have been explored for their potential to enhance the photocatalytic capabilities of TiO₂. The review aims to provide a comprehensive overview of the latest advancements in ion-modified TiO₂ photocatalysts, highlighting the strategies employed and their effects on photocatalytic hydrogen production. The findings contribute to the development of advanced TiO₂-based photocatalysts for efficient water-splitting applications, addressing the challenges of energy scarcity and environmental degradation.