A Beehive Inspired Hydrogen Photocatalytic Device Integrating a Carbo‐Benzene Triptych Material for Efficient Solar Photo‐Reduction of Seawater

Abstract The dream to produce green, clean, and sustainable hydrogen from earth‐abundant and free resources such as seawater and sunlight is highly motivating because of the interest for desirable economical and societal applications in energy. However, it remains challenging to develop an efficient and unassisted photocatalytic device to split seawater molecules with just sunlight without any external bias. For the first time, a such novel hierarchical material has been developed, based on thin film technology that integrates TiO 2 semiconductor layers, embedded gold nanoparticles, and a photosensitive carbo‐benzene layer. The design of the triptych device placing the photocatalyst in be‐to‐be increases the photoactive surface area by a factor 2. Its stability (>120 successive hours of hydrogen production and >5 days in a day/night representative alternation) and efficiency (Soler‐to‐Hydrogen 0.06%) are measured in NaCl‐salted water. The chloride ions act as hole scavengers and induce an increase of pH increasing in turn the sun‐driven hydrogen production rate.