Abstract : The excessive consumption of fossil fuels required for energy production results in harmful pollution and CO2 emissions causing climate changes. Therefore, many researchers focus on clean energy sources, and development of active materials to produce and store sustainable energy, reduce carbon emissions, and promote sustainability.
In this context, hydrogen (H2) is a promising solution to reduce our dependence on fossil resources as it is a clean energy vector that could solve problems related to energy use, CO2 emissions and environmental pollution. However, it must be produced from green resources! Photocatalysis offers a promising way to produce green H2 from water considering the possibility of coupling this technique to a renewable energy source such as sunlight. However, before to achieve this, efficient and durable photocatalysts are required. Considering this challenge, this doctoral research focuses on the development of composite nanomaterials based on copper (Cu) or nickel (Ni) Metal Organic Frameworks (MOFs) and titanium dioxide (TiO2) for hydrogen generation by photocatalysis.
These photoactive composite materials were characterized by various techniques such TEM, UV-visible spectroscopy, infra-red spectroscopy, photo-electrochemical techniques, and XPS.  The photocatalytic mechanisms were also investigated by time resolved microwave conductivity (TRMC) and EPR studies. The photocatalytic activity for hydrogen generation of the MOF-composite nanomaterials were compared with those of TiO2 surface-modified with metal nanoparticles (Pt and Cu) induced by radiolysis. These composites display a synergistic effect that leads to less electron-hole recombination and induces higher hydrogen generation under visible light. The MOFs-based on copper exhibited a very high photocatalytic activity, which increased with cycling. Reduction of Cu and formation of very small clusters of copper (0) are expected to be responsible for this increased photocatalytic activity.  DFT calculations were also conducted to understand the photocatalytic mechanism and the role of copper in H2 generation. Ni-based MOFs exhibit also very promising photocatalytic activities for hydrogen generation. It is expected that our results will help the development of very active and sustainable materials for photocatalytic solar fuels’ generation.