​The main project supported by the Photocatalysis Lab aims at producing hydrogen from water using sunlight through a photocatalytic process. To this end, several key steps have been identified:

• Establish guidelines and photocatalyst activity descriptors to select a set of potentially active photocatalysts

• Proof of concept

• Identify the best hit

• Catalyst scale-up

• Build a pilot unit for photocatalysts field test

The photocatalytic water splitting has been pioneered 30 years ago and has advanced since then through the work of various groups, including the group of Prof. Domen (the University of Tokyo). Using UV light as an irradiation source, some photocatalysts have been reported to achieve overall water splitting with a quantum efficiency much higher than 10%. However, solar light contains only 4% of its energy in the UV region while over 40% of the energy is in the visible region. In an attempt to utilize more solar energy, the research program aims at developing photocatalysts responsive in the visible region of the solar spectrum. The ultimate goal is to engineer photocatalysts with twice the current state of the art efficiency in the visible region to reach an overall 10% solar to hydrogen energy conversion efficiency. The research team (PI: Kazuhiro Takanabe) is specifically focused on improving absorption in a wide range of the visible region and to enhance quantum efficiency through:

• The synthesis of semiconductor materials (e.g: new (oxy)nitrides) with high crystallinity and large absorption band

• The introduction of active electrocatalysts and/or semiconductor layers

Material synthesis is achieved using a variety of types of furnaces (flow in various gas atmospheres, batch in air, rapid temperature ramping). Photocatalytic tests are conducted using recirculating and flow reactors, equipped with various light sources (high pressure Hg, Xe, solar simulator etc.) and gas chromatographies. Wavelengths are selected by using various cutoff and band pass filters. Photon numbers at each wavelength are accurately measured using various photodiodes. Liquid reactants and products are measured by HPLC for organic and inorganic compound analysis and ionic HPLC for ion analysis. Photocatalyst materials are characterized using XRD, XPS, FTIR, photoluminescence and UV-VIS spectroscopy. A series of (photo)electrochemistry equipment is available for understanding of band positions and semiconductor properties using potentiostats with various electrodes.