Solar Reduction of CO2 at Nano-Architectured Photoelectrodes Featuring Advanced Photon Management

• Applicant: Ryan Crisp, Ph.D.
• Subject Area: Synthesis and Properties of Functional Materials
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465220299

Even though renewable technology is rapidly progressing and could provide for our electricity, effective use of green energy sources to drive chemical reactions remains challenging. There are 3 crucial conditions for redox chemical reactions: the necessary number of reactants + electrons, the proper energy levels, and overcoming any activation barrier. One main limitation preventing solar fuel production is the necessity for multiple electron transfers to the reactants. The aim of the proposal is to design unprecedented photoelectrodes: a CO2 reduction cathode and an H2O oxidation anode in the “Z-scheme”. The consortium partners consisting of two experienced research groups from FAU and IMP PAN propose to exploit highly ordered substrates that yield advanced three-dimensional electrodes in solar driven reactor. It is expected that efficient sunlight-driven fuel production can be achieved via water oxidation combined with CO2 reduction (artificial photosynthesis). The project includes an optimized fabrication route of the materials and their detailed characterization. The photoanode will consist of ordered titania nanotubes with the light absorber (Sb2S3) and catalyst (Ir/V2O5). The photocathode is an alumina template with quantum dots (QDs) as a light absorber exhibiting carrier multiplication (CM) and Cu/Cu2O as a catalyst. The titania nanotubes and alumina template will be obtained via anodization – a technique using only simple, low-cost equipment. These two materials will be constructed into a tandem cell for complete artificial photosynthesis. Because of the modular design, illumination can be done independently, from opposite sides, or sequentially thereby offering flexibility to explore fundamental processes. The following hypotheses are proposed: a) Increasing geometric surface area using nanostructuring will improve each half-reaction. b) QD band-levels can be tuned to drive CO2 reduction. c) Carrier multiplication will increase reaction kinetics. d) Tandem cells with these concepts allow more efficient artificial photosynthesis. To verify the hypotheses, the consortium partners will implement the following procedure: (I) photoanode: a) deposit a Ti layer; b) form a transparent electron collector out of the deposited metallic layer; c) deposit the light absorber onto the ordered titania; d) deposit the catalytic film and (II) for the photocathode: a) fabrication of the hole collector; b) attach the QD light absorber featuring CM; c) add a catalyst. For both electrodes: a) characterization of the morphology and structure, b) characterization of opto-electronic and functional properties, d) construction of tandem cells. We propose a unique approach to fabricate and characterize tandem cells with CM for complex chemical reactions never reported before. We foresee that the project’s realization brings new insights into the development of tailored surfaces and structures for CO2 reduction and fundamental science of CM in advanced materials.

• DFG Programme: Research Grants
• International Connection: Poland
• Partner Organisation: Narodowe Centrum Nauki (NCN)
• Co-Investigator: Professor Dr. Julien Bachmann, Ph.D.
• Cooperation Partners: Dr. Katarzyna Grochowska; Dr.-Ing. Katarzyna Siuzdak, Ph.D.