Dielectric properties and electrical conductivity as predictors of catalytic selectivity

• Applicant: Peter Kraus, Ph.D.
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 490703766

Heterogeneous catalysis is one of the key processes in the manufacture of fine chemicals, polymers, and other products. However, despite the progress in our understanding of heterogeneous catalysis, the goal of creating a heterogeneous catalyst by systematic design rather than serendipitous discovery remains elusive. This is due to several challenges, including the multi-scale nature of catalysis in both space and time, experimental challenges in direct observation of active sites and reaction intermediates, the extended and complex nature of catalytic surfaces complicating computational modelling, as well as the lack of standardised data reporting hindering data-scientific approaches.This project aims to address these issues by using the dielectric properties and the electrical conductivity of materials as: 1) an experimental probe of the catalytic material and its surface under oxidative and inert conditions, as well as a probe of the active site under operando conditions; 2) a validation target for computational methods to develop a method for the deconvolution of bulk, surface, and gas-phase contributions to the dielectric permittivity and electrical conductivity; and 3) a source of high-quality kinetic data from operando experiments designed to underpin a microkinetic model, with the aim to describe the catalytic as well as dielectric and electrical properties of the material.The project will initially involve the experimental investigation and computational modelling of binary metal oxides, including but not limited to the oxides of vanadium, molybdenum, tellurium, and niobium. A second-generation contactless microwave cavity instrument will be developed as part of this project, allowing for a precise and reproducible measurement of the electrical conductivity under operating conditions. The cavity experiments will be supplemented by a broadband frequency-resolved conductivity measurement, also developed during the project, to supply further data for computational modelling.In the second stage of this project, the focus will shift to applying the developed methods to the bronze-like M1 structure of various molybdenum vanadates. The catalytic performance of the quinary Mo-V-Te-Nb-O material is particularly remarkable due to its selectivity to acrylic acid, among other possible applications. This project aims to further describe the dynamic active surface of the catalyst, by modelling the changes in the operando dielectric permittivity and electrical conductivity using microkinetic approaches and computational data.

• DFG Programme: Independent Junior Research Groups