The project PROPHECY – PROcess concepts for PHotocatalytic CO2 reduction associated with lifE-CYcle analysis (033RC003) – is funded by the German Ministry of Education and Research (BMBF) within the scope of the funding line CO2Plus (www.chemieundCo2.de) for a period of three years. The project is a collaboration with the groups of Prof. Dr. Michael Wark, University of Oldenburg, Dr. Andreas Patyk, ITAS at the Karlsruhe Institute of Technology and Prof. Dr. Reinhard Schomäcker at Technical University Berlin.
In our previous studies (BMBF project PhotoKat, 033RC1007A, October 2010 to March 2016) it was clearly demonstrated that a reaction atmosphere consisting of only CO2 and H2O is very unreactive on commercial photocatalysts such as ZnO or TiO2. Completely new processes and photocatalysts for photocatalytic CO2 reduction thus have to be found. In PROPHECY, the group of Michael Wark thus explores the development and optimization of new photocatalyst structures and materials, while the Strunk group looks into alternative process conditions using renewable additives. The group of Reinhard Schomäcker investigates the photocatalytic dry-reforming of methane (CH4 + CO2, possibly biogas) and the scaling up of the photocatalytic reactor. Lastly, Andreas Patyk and his group perform sustainability considerations of the newly developed catalysts and reaction conditions to early on guide research and development towards ecological and economic feasibility.
Subproject Process Conditions (Strunk)
The central question explored in this subproject is the feasibility of the addition of more reactive substances to the feed gas for the increase of yields and the modification of the product distribution, e.g. to entirely different products or longer hydrocarbon chains. It is important that all additives considered in this project are in principle accessible from a renewable resource. In this respect, the use of hydrogen from water electrolysis using wind or solar power, the addition of bioethanol and other substances will be tested. The high-purity gas-phase photoreactor system will be used for those studies, so the product distribution can be analyzed even down to the smallest trace contents.
Subproject Catalyst Development (Wark)
The Wark group explores both new synthesis routes and new structures of known photocatalysts such as TiO2 and ZnO, but also develops completely new materials (e.g. titanates), particularly with the aim to use a larger part of the solar irradiation. Whenever possible, abundant and widely accessible materials are used. It is the aim to develop easily scalable synthesis methods, in principle viable for the industrial scale. Together with material synthesis, crucial structural and electronic properties are identified and optimized, such as porosity and charge transfer properties, and their importance for the photocatalytic process is evaluated.
Subproject Sustainability considerations (Patyk)
Photocatalytic CO2 reduction, just like any other chemical production process, does not work on its own. Instead, it necessitates a variety of pre- and posttreatment steps, resources are needed, and waste is created. Currently, it is unknown if such a process, often claimed to enable “CO2 recycling”, is in fact ecologically and economically useful, when all pre- and post-processes are additionally taken into account. The group of Dr. Andreas Patyk addresses this question in sustainability considerations, to evaluate how much useful product must be synthesized under which circumstances to make the process feasible and sustainable. The early integration of sustainability considerations into the whole project allows influencing and redirecting R&D into useful directions continuously.
Subproject Process Conditions (Schomäcker)
This subproject is focused on two major aspects. First part of the project is the investigation of the mechanism of photocatalytic dry reforming of CO2 and methane. The reaction conditions will be varied within a wide range of parameters of catalytic and photocatalytic reactions to identify the rate-determining step of the reaction and the most important intermediates. The second part will focus on the transferability of the results and the reaction conditions from lab scale to large scale application.