Electrochemical Synthesis of TiO2 Nanotubes for Photocatalytic Water Splitting: Mechanisms, Challenges, and Improvement Strategies

Nowadays, due to strategic reasons such as the importance of energy and environmental protection, the demand for alternatives to fossil fuels has surged. Hydrogen is considered a suitable and potential alternative energy source, promoting the development of various production technologies. However, conventional technologies for hydrogen production generate a large amount of CO2 greenhouse gases, contributing to serious environmental issues. In recent decades, TiO2 nanotubes have emerged as effective photocatalysts for electrode reactions involving water splitting, resulting in hydrogen production. These photocatalysts utilize readily available resources: water as the raw material and sunlight as the energy source. Despite their potential, TiO2 nanotubes face substantial challenges, including a large energy gap resulting in very low electrical conductivity, along with the recombination of electrons and electron holes during the water splitting reaction. These issues present considerable obstacles to the integration of these materials into the industrial cycle of new energy production, particularly hydrogen generation. Currently, the challenges and potential solutions associated with TiO2 have made it one of the most extensively researched materials worldwide. In this review, the status of photocatalysts based on TiO2 nanotubes is examined, highlighting the main challenges in this field and the proposed solutions to address these obstacles.