Michael Gráutzel

Bio: Michael Gráutzel is an academic researcher from École Polytechnique. The author has contributed to research in topics: Visible spectrum & Aqueous solution. The author has an hindex of 1, co-authored 1 publications receiving 163 citations.

Visible Light Induced Water Cleavage in CdS Dispersions Loaded with Pt and RuO2, Hole Scavenging by RuO2

Abstract: Illumination of aqueous CdS dispersions loaded with Pt and RuO2 by visible light produces hydrogen and oxygen in stoichiometric proportion. No degradation of the photocatalyst is noted after 60 h of irradiation time. The RuO2 deposit on the particle surface greatly accelerates the transfer of holes from the semiconductor valence band to the aqueous solution thus inhibiting photocorrosion.

All-solid-state Z-scheme in CdS-Au-TiO2 three-component nanojunction system.

Abstract: Natural photosynthesis, which achieves efficient solar energy conversion through the combined actions of many types of molecules ingeniously arranged in a nanospace, highlights the importance of a technique for site-selective coupling of different materials to realize artificial high-efficiency devices1. In view of increasingly serious energy and environmental problems, semiconductor-based artificial photosynthetic systems consisting of isolated photochemical system 1 (PS1), PS2 and the electron-transfer system have recently been developed2,3. However, the direct coupling of the components is crucial for retarding back reactions to increase the reaction efficiency. Here, we report a simple technique for forming an anisotropic CdS–Au–TiO2 nanojunction, in which PS1(CdS), PS2(TiO2) and the electron-transfer system (Au) are spatially fixed. This three-component system exhibits a high photocatalytic activity, far exceeding those of the single- and two-component systems, as a result of vectorial electron transfer driven by the two-step excitation of TiO2 and CdS.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

Abstract: In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.

Mechanism of reactions on colloidal microelectrodes and size quantization effects

Abstract: Small particles of metals in solution often behave like electrodes although they are not connected to a battery which determines their potential. However, when a chemical reaction occurs in the solution of such particles intermediate free radicals may transfer electrons to them. The particles are thus charged chemically and are able to act as a metal electrode on cathodic potential. Electron transfer reactions become possible at these micro-electrodes which cannot be brought about by the radicals in the absence of the colloidal catalyst.

Photocatalytic CO2 reduction by CdS promoted with a zeolitic imidazolate framework

Abstract: Metal organic frameworks (MOFs) have emerged as a new class of multifunctional porous materials, and more particularly the family of zeolitic imidazolate frameworks (ZIFs) have shown great promise in the applications of carbon dioxide capture and storage. The CO 2 photoreduction system was established by employing CdS semiconductor and Co-ZIF-9 to act as a catalyst and a cocatalyst, respectively. This hybrid system cooperating with bipyridine and triethanolamine exhibits high catalytic activity in the deoxygenative conversion of CO 2 to CO under visible light irradiation at mild reaction conditions. 13 CO 2 isotopic experiment validated that the produced CO was from the photoreduction of CO 2 , instead of organics in the system. The effect of parameters such as cocatalyst concentration, reaction temperature, solvent properties, and water effect were investigated in details. Under the optimized reaction conditions, a high apparent quantum yield of 1.93% was achieved under monochromatic irradiation of 420 nm. The uniqueness of Co-ZIF-9 in supporting CdS for CO 2 reduction reaction was explored by comparing its catalytic functions with other MOFs. In-situ photoluminescence and photocurrent generation measurements demonstrated the function of Co-ZIF-9 for promoting electron transfers. At last, a possible reaction mechanism of the photoreduction reaction was proposed.