One of the major challenges of the renewable energy transition is to supply energy even in the absence of sunlight. Hydrogen production by splitting water with the help of sunlight could offer a solution. Hydrogen is a good energy storage medium, and can be used in many ways. However, catalysts are needed to split water. Platinum is often used, but it is rare and expensive. Researchers therefore seek more economical alternatives. Now, a team headed by Dr. Tristan Petit from the HZB, together with colleagues led by Prof. Bin Zhang from Tianjin University, Tianjin, China, has made important progress using a well-known class of metal-free photocatalysts.