Hydrogen, known for producing only water when burned or used in fuel cells, has emerged as a promising solution to reduce global carbon emissions. However, most hydrogen production today involves fossil fuels, releasing significant carbon dioxide into the atmosphere. To tackle this issue, a group of researchers led by Professors Takashi Hisatomi and Kazunari Domen has developed a groundbreaking method to create carbon-free hydrogen. The researchers built a 100-square-meter reactor that utilizes sunlight and photocatalysts to split water into hydrogen and oxygen directly. This innovative approach bypasses traditional methods that involve converting sunlight into electricity before splitting water. By submerging sheets of a photocatalyst called SrTiO3:Al in water, sunlight activates the photocatalyst, leading to the separation of water molecules into hydrogen and oxygen gases, which can be collected for storage and use. Unlike conventional methods that suffer energy losses at each conversion stage, this direct process minimizes inefficiencies. Despite the method's unparalleled concept, the efficiency of current systems remains a challenge, achieving only one percent efficiency under simulated sunlight and less than five percent under natural sunlight. Efforts are underway to enhance the efficiency by improving photocatalyst materials, which are crucial for scaling up this technology. Carbon-free hydrogen production, although facing scaling issues, presents a promising pathway to cleaner energy and industries. With advancements in photocatalyst materials and increased investment, this technology could potentially transform hydrogen production, accelerating the shift towards a carbon-free economy. The significance of this innovation is amplified in the context of combating climate change, where cleaner energy sources are urgently needed.