Photoelectrochemical CO2 conversion with tunable semiconductor nanostructures

• Applicants: Dr. Lutz Geelhaar; Matthew Mayer, Ph.D.
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 442704684

The use of solar energy to convert carbon dioxide (CO2) into valuable chemicals is an attractive way towards a sustainable carbon cycle that reduces our society's fossil fuel dependence and greenhouse gas emissions. One promising concept is "artificial photosynthesis", which combines sunlight-absorbing and catalytic components in an integrated system powered only by sunlight, water and CO2. However, practical implementation is hampered by the complexity of catalytic CO2 conversion which follows multi-step, energy-intensive reactions leading to various possible products. Our goal is to use a tunable model system to gain a deeper understanding of the multilayered interaction of the relevant semiconductor–electrolyte processes and their influence on energy conversion efficiency and product selectivity.We use a photoelectrochemical approach that provides the control necessary for precise studies. Our key innovation is the use of ordered (In,Ga)N nanowire arrays as photoelectrodes with well-defined, adjustable properties (composition, doping, morphology) which affect both light harvesting and electrocatalytic behaviors. We will study how nanoscale morphology (nanowire length and diameter, array geometry) can influence catalytic selectivity by affecting transport processes, as well as enhance light absorption. We will additionally analyze how tuning of the semiconductor electronic structure, particularly the conduction band edge, may affect the product selectivity through varying the thermodynamic driving force for the reaction. Since the photoelectrochemical approach allows control over the reaction rate by modulating the light intensity, we can uniquely decouple thermodynamic and kinetic effects to enable systematic investigation of the complex interplay influencing photoelectrochemical CO2 conversion. These results will provide valuable insights for the development of efficient and scalable integrated systems for sunlight-driven renewable chemical synthesis.

• DFG Programme: Research Grants
• Co-Investigators: Dr. Peter Bogdanoff; Dr. Oliver Brandt; Professor Dr. Roel van de Krol