Project Details
Projekt
Correlating active catalyst states and oxygen evolution reactivity in in-situ Environmental Transmission Electron Microscopy (ETEM) experiments
Subject Area
Physical Chemistry of Solids and Surfaces, Material Characterisation
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 544637349
The comprehensive understanding of the real structure of the electrocatalyst water interface on the atomic scale is essential for breaking the limits in electrochemical water splitting due to the sluggish oxygen evolution reaction. The main goal of this proposed project is correlating active states and oxygen evolution reactivity (OER) in atomic-resolution in-situ ETEM experiments using well-defined spinel-type nanoparticles AIIBIIIO4 with tunable chemical composition and precise crystalline surface facets. The key new step is the establishment of a highly sensitive local mass spectrometry probe close to the TEM specimen for the measurement of reaction products of nanoscale electron transparent electrodes in order to correlate observation of interface reconstruction and dynamics to reactivity. This is essential to substantiate the relevance of in-situ atomic scale observations for conditions that are close to applications. We select the bimetallic NiCo2O4, CoMn2O4 compounds as well as a Ni-doping series NixCo3-xO4 nanoplates (0 <=x<=1) for this study, since their activity can be strongly tuned by cation doping and they can be synthesized with well-defined size, morphology and surface orientations. Bimetallic spinels are of particular interest since they typically show a higher OER activity compared to their monometallic counterparts (Fe3O4, Mn3O4 and Co3O4) as reference. Nanoplates are chosen since they represent electron transparent electrodes without the need of TEM lamella preparation by ion milling that always lead to quite strong modifications of the catalyst surface. The new local probe mass spectroscopy setup will be developed by a modification of an existing gas and liquid cell biasing TEM sample holder. A micro-scale capillary is connected to a gas tube and attached to the counter electrode allowing to measure reaction products of OER in water vapor under an applied bias using a highly sensitive quadrupole mass spectrometer. The setup will be tested by comparing the active state of the interface to H2O of nanoplates with low and with high OER activity as a model system. We will calibrate the O2 turn over by comparison with measurements of the OER activity of the same nanoparticles in standard electrochemical conditions. This will allow the establishment of trends in correlation of active state of the electrocatalyst with different Ni doping to activity and stability. As a goal for a second period of the project, we aim for the detection of low mass reaction products other than O2 with sufficient lifetime in order to study electron beam induced ion formation, catalytic side reaction or intermediate products. Altogether, our project will help identifying mechanisms for the extraordinarily high OER in Ni-doped Co3O4 beyond the limitations of scaling relations, while developing a comprehensive understanding of the chemical environment of samples in in-situ TEM experiments.
DFG Programme
Research Grants
Major Instrumentation
Quadrupole Mass Spectrometer
