Fossil fuels play a vital role in supplying energy to the world population. However, utilizing fossil fuels causes the emission of greenhouse gases, which are implicated in global warming and climate change. Therefore, alternative energy sources should be implemented. Hydrogen appears to be an environmentally friendly form of energy. In principle, it can be produced simply via the photocatalytic splitting of water, where excited electrons generated from the photocatalyst are responsible for the reduction of protons to produce hydrogen. In the past few decades, an enormous amount of work has been done in this area. We report that under ultraviolet (UV) illumination, zinc oxide facilitates the photocatalytic splitting of water to produce hydrogen. The efficiency of zinc oxide as a photocatalyst can be improved through bandgap engineering. The bandgap of zinc oxide can be tuned so that it will absorb not only the ultraviolet but also the visible light. Consequently, a great fraction of the solar spectrum can be absorbed to produce more excited electrons, and eventually hydrogen. In order to provide more reaction sites, mesoporous zinc oxide has been synthesized. The fabrication step involves using mesoporous carbon as a template, which can be easily removed by calcination. The structure of the resultant material and the process of photocatalytic splitting of water are also discussed.