The global pursuit of clean and renewable energy has spotlighted hydrogen as a sustainable fuel, particularly when generated through environmentally friendly methods. Among these, photoelectrochemical (PEC) water splitting stands out as a direct and solar-powered approach to hydrogen (H₂) production. Unlike conventional techniques that rely heavily on fossil fuels, PEC systems utilize semiconductor materials to absorb sunlight and catalyze the splitting of water into hydrogen and oxygen, without releasing harmful byproducts. This makes PEC technology a viable candidate for future green energy systems.

A key factor influencing the efficiency of photoelectrochemical (PEC) systems is the careful choice and fine-tuning of semiconductor materials. Among these, metal oxides like titanium dioxide (TiO₂) have gained significant attention, primarily because of their natural abundance and excellent chemical stability.. However, TiO₂’s large band gap (~3.2 eV) restricts its light absorption to the ultraviolet region, which constitutes a small fraction of the solar spectrum . To overcome this, material scientists have employed doping techniques—introducing foreign atoms into the semiconductor lattice—to tailor its electronic structure and extend absorption into the visible light range. For example, doping TiO₂ with elements like silver, nitrogen, or carbon has been shown to narrow its band gap and facilitate more efficient photon utilization.

Beyond doping, the construction of heterojunctions—interfaces between different semiconductor materials—further improves PEC performance. These structures enhance charge carrier separation and reduce recombination losses by establishing internal electric fields that drive electrons and holes in opposite directions. 2D heterojunctions, in particular, offer advantages due to their large surface area and short charge transport paths, making them ideal platforms for high-efficiency solar-driven catalysis .

This report focuses on how doping alters the electronic and optical properties of semiconductors, with an emphasis on TiO₂-based materials. We discuss current advancements in material engineering, the role of dopants in modifying charge transport and absorption behavior, and the future potential of doped semiconductors in large-scale hydrogen production. As research continues to bridge material limitations, PEC water splitting—empowered by advanced doping strategies—moves closer to becoming a cornerstone of the hydrogen economy.

Keywords-Photoelectrochemical, Nanoscale, Metal Oxide, steam methane reforming, Hydrogen Generation

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1. Ahmad H, Kamarudin SK, Minggu LJ, Kassim M. Hydrogen from photo-catalytic water splitting process: A review. Renewable and Sustainable Energy Reviews. 2015 Mar 1;43:599-610.
2.  Wei LC, Chau JHF. Photoelectrochemical water splitting process using titanium dioxide photocatalyst: a brief overview. Malays Catal – Int J. 2021;1:26–35.
3. Ren X, et al. NiO/Ni/TiO₂ nanocables with Schottky/p–n heterojunctions and improved photocatalytic performance in water splitting under visible light. J Colloid Interface Sci. 2018;530:1–8.
4. Marwat MA, et al. Advanced catalysts for photoelectrochemical water splitting. ACS Appl Energy Mater. 2021;4(11):12007–31.
5. Miller EL. Photoelectrochemical water splitting. Energy Environ Sci. 2015;8(10):2809–10.
6. Liu B, Wang S, Zhang G, Gong Z, Wu B, Wang T, Gong J. Tandem cells for unbiased photoelectrochemical water splitting. Chemical Society Reviews. 2023;52(14):4644-71.
7. Ren X, et al. NiO/Ni/TiO₂ nanocables with Schottky/p–n heterojunctions and improved photocatalytic performance in water splitting under visible light. J Colloid Interface Sci. 2018;530:1–8.
8. Marwat MA, et al. Advanced catalysts for photoelectrochemical water splitting. ACS Appl Energy Mater. 2021;4(11):12007–31.
9. Wei LC, Chau JHF. Photoelectrochemical water splitting process using titanium dioxide photocatalyst: a brief overview. Malays Catal – Int J. 2021;1:26–35.
10. Miller EL. Photoelectrochemical water splitting. Energy Environ Sci. 2015;8(10):2809–10.
11. Sathre R, Greenblatt JB, Walczak K, Sharp ID, Stevens JC, Ager JW, Houle FA. Opportunities to improve the net energy performance of photoelectrochemical water-splitting technology. Energy & Environmental Science. 2016;9(3):803-19.
12. Liu B, et al. Tandem cells for unbiased photoelectrochemical water splitting. Chem Soc Rev. 2023.
13. Marwat MA, et al. Advanced catalysts for photoelectrochemical water splitting. ACS Appl Energy Mater. 2021;4(11):12007–31.
14. Ren X, et al. NiO/Ni/TiO₂ nanocables with Schottky/p–n heterojunctions and improved photocatalytic performance in water splitting under visible light. J Colloid Interface Sci. 2018;530:1–8.
15. Yoo IH, Kalanur SS, Seo H. A nanoscale p–n junction photoelectrode consisting of an NiOx layer on a TiO2/CdS nanorod core-shell structure for highly efficient solar water splitting. Applied Catalysis B: Environmental. 2019 Aug 5;250:200-12.

The global pursuit of clean and renewable energy has spotlighted hydrogen as a sustainable fuel, particularly when generated through environmentally friendly methods. Among these, photoelectrochemical (PEC) water splitting stands out as a direct and solar-powered approach to hydrogen (H₂) production. Unlike conventional techniques that rely heavily on fossil fuels, PEC systems utilize semiconductor materials to absorb sunlight and catalyze the splitting of water into hydrogen and oxygen, without releasing harmful byproducts. This makes PEC technology a viable candidate for future green energy systems.

A key factor influencing the efficiency of photoelectrochemical (PEC) systems is the careful choice and fine-tuning of semiconductor materials. Among these, metal oxides like titanium dioxide (TiO₂) have gained significant attention, primarily because of their natural abundance and excellent chemical stability.. However, TiO₂’s large band gap (~3.2 eV) restricts its light absorption to the ultraviolet region, which constitutes a small fraction of the solar spectrum . To overcome this, material scientists have employed doping techniques—introducing foreign atoms into the semiconductor lattice—to tailor its electronic structure and extend absorption into the visible light range. For example, doping TiO₂ with elements like silver, nitrogen, or carbon has been shown to narrow its band gap and facilitate more efficient photon utilization.

Beyond doping, the construction of heterojunctions—interfaces between different semiconductor materials—further improves PEC performance. These structures enhance charge carrier separation and reduce recombination losses by establishing internal electric fields that drive electrons and holes in opposite directions. 2D heterojunctions, in particular, offer advantages due to their large surface area and short charge transport paths, making them ideal platforms for high-efficiency solar-driven catalysis .

This report focuses on how doping alters the electronic and optical properties of semiconductors, with an emphasis on TiO₂-based materials. We discuss current advancements in material engineering, the role of dopants in modifying charge transport and absorption behavior, and the future potential of doped semiconductors in large-scale hydrogen production. As research continues to bridge material limitations, PEC water splitting—empowered by advanced doping strategies—moves closer to becoming a cornerstone of the hydrogen economy.

Keywords-Photoelectrochemical, Nanoscale, Metal Oxide, steam methane reforming, Hydrogen Generation

🔒 This is a subscription article

Full text is available to subscribers and institutional members. Please choose an option below to access it.

1. Ahmad H, Kamarudin SK, Minggu LJ, Kassim M. Hydrogen from photo-catalytic water splitting process: A review. Renewable and Sustainable Energy Reviews. 2015 Mar 1;43:599-610.
2.  Wei LC, Chau JHF. Photoelectrochemical water splitting process using titanium dioxide photocatalyst: a brief overview. Malays Catal – Int J. 2021;1:26–35.
3. Ren X, et al. NiO/Ni/TiO₂ nanocables with Schottky/p–n heterojunctions and improved photocatalytic performance in water splitting under visible light. J Colloid Interface Sci. 2018;530:1–8.
4. Marwat MA, et al. Advanced catalysts for photoelectrochemical water splitting. ACS Appl Energy Mater. 2021;4(11):12007–31.
5. Miller EL. Photoelectrochemical water splitting. Energy Environ Sci. 2015;8(10):2809–10.
6. Liu B, Wang S, Zhang G, Gong Z, Wu B, Wang T, Gong J. Tandem cells for unbiased photoelectrochemical water splitting. Chemical Society Reviews. 2023;52(14):4644-71.
7. Ren X, et al. NiO/Ni/TiO₂ nanocables with Schottky/p–n heterojunctions and improved photocatalytic performance in water splitting under visible light. J Colloid Interface Sci. 2018;530:1–8.
8. Marwat MA, et al. Advanced catalysts for photoelectrochemical water splitting. ACS Appl Energy Mater. 2021;4(11):12007–31.
9. Wei LC, Chau JHF. Photoelectrochemical water splitting process using titanium dioxide photocatalyst: a brief overview. Malays Catal – Int J. 2021;1:26–35.
10. Miller EL. Photoelectrochemical water splitting. Energy Environ Sci. 2015;8(10):2809–10.
11. Sathre R, Greenblatt JB, Walczak K, Sharp ID, Stevens JC, Ager JW, Houle FA. Opportunities to improve the net energy performance of photoelectrochemical water-splitting technology. Energy & Environmental Science. 2016;9(3):803-19.
12. Liu B, et al. Tandem cells for unbiased photoelectrochemical water splitting. Chem Soc Rev. 2023.
13. Marwat MA, et al. Advanced catalysts for photoelectrochemical water splitting. ACS Appl Energy Mater. 2021;4(11):12007–31.
14. Ren X, et al. NiO/Ni/TiO₂ nanocables with Schottky/p–n heterojunctions and improved photocatalytic performance in water splitting under visible light. J Colloid Interface Sci. 2018;530:1–8.
15. Yoo IH, Kalanur SS, Seo H. A nanoscale p–n junction photoelectrode consisting of an NiOx layer on a TiO2/CdS nanorod core-shell structure for highly efficient solar water splitting. Applied Catalysis B: Environmental. 2019 Aug 5;250:200-12.