Prof. Dr. Tong Li • Prof. Dr. Kristina Tschulik
In the second funding period (FP2), B09 developed a multimodal method that correlates electron backscatter diffraction/scanning electrochemical cell microscopy (KT and TL), electrochemical atomic force microscopy (KT), X-Ray photoelectron spectroscopy (S project), and atom probe tomography (TL) to reveal the surface transformation on Co-Fe, Co-Mn, Co-Cr mixed spinels and different facets of Co oxyhydroxides and spinels toward oxygen evolution reaction (OER). We demonstrated that the activity and stability of Co spinels are highly associated with surface transformation during OER. A similar surface transformation is hypothesized to influence the selectivity and activity of the Co-based spinels during alcohol oxidation, but the precise mechanisms remain elusive. Herein, B09 will investigate the effect of surface transformation on selectivity and activity of Co-based spinels toward the oxidation of alcohols, including ethylene glycol and isopropanol. We hypothesize that defects generated by mixing Co spinels with different amounts of other 3d transition metal cations, such as Ni and V (defects at metal sites) or doping the oxygen lattice with N (oxygen vacancies), favour transitions into catalytically active surface species, thereby affecting the activity and selectivity of alcohol oxidation.
To verify our hypothesis and derive design citeria for high perfomance alcohol catalysts, we will employ the multimodal method we established in FP2 to identify the effect of surface transformations on the activity and selectivity of 1) electrodeposited mixed Co-Ni spinel films, 2) Co-M (M: V, Cr, Ni) spinels, and 3) N-doped Co-M spinels toward alcohol oxidation and OER. In addition, we will combine in situ Raman spectroscopy with our combined spectroscopy and microscopy techniques before, during and after alcohol oxidation to grasp a holistic understanding of how catalyst transformations and catalyst performance are interconnected and how to steer them by cation and anion defects. Overall, B09 aims to clarify the role of surface transformation in the selectivity and activity of Co-based spinels for alcohol oxidation and compares the knowledge with those derived from OER to generalize knowledge regarding how point defects in the cation and anion lattice can be used to tune catalyst transformations and, thus, influence the activity and selectivity towards oxidation catalysis in the liquid phase. The gained understanding will allow us to provide design criteria for high performance OER and alcohol oxidation catalysts as a key outcome of FP3.
Figure: Scheme of the correlative method established in FP2 linking electrochemical measurements with local structure, composition, and elemental distribution of the surface species formed during OER. Adapted from publication.
B09: Exploring the Role of Defects on the Active Site Evolution in Co-Based Spinels and Hydrous Oxides under OER Conditions by Correlative Microscopy
Co-based oxides and hydrous oxides have emerged as promising electrocatalysts for the oxygen evolution reaction (OER). Further improving these electrocatalysts requires detailed knowledge of structure-property relationships. However, the electrochemical performance of electrocatalysts may differ spatially due to the presence of surface defects, while standard electrochemical analysis probes the entire electrode surface, providing integral data. Moreover, electrocatalysts undergo dynamic changes in surface-near regions under OER conditions. Therefore, an approach that can reveal the local surface structure and correlate it with the local activity is urgently needed.
In this project, we will develop a correlative method to link the oxidation state, surface morphology and chemical compositions of Co-based oxides and hydrous oxides with their local activity. The new method will enable the correlation of scanning electrochemical cell microscopy (SECCM), electrochemical atomic force microscopy (EC-AFM), X-Ray photoelectron spectroscopy (XPS), and atom probe tomography (APT) measurements on the same local features that are pre-identified by the scanning electron microscopy (SEM)/electron backscatter diffraction (EBSD). We will focus on the Co-X (X: Fe, Mn) spinel oxides and hydrous oxides in the form of nanoparticles or thin films synthesized by electrochemical oxidation of Co. Specifically, SECCM will be employed to probe the local OER activity on the surface of oxides and hydrous oxides. APT in conjunction with EC-AFM and SEM/EBSD will be used to reveal the morphology, chemical composition, and local defects on the surface of oxides and hydrous oxides and their temporal evolutions during OER.
Overall, the project will improve the understanding of the structure-property relationships of Co-based oxides and hydrous oxides, with focus on the role of well-defined defects, such as grain boundaries. Since we will be able to identify and localize different crystal planes on the samples and link them to the local OER activity and associated morphological changes, jointly with the insights gained from theory and operando spectroscopy within the consortium, this project will give new insights into the active sites of Co-based spinels and hydrous oxides for OER. This new correlative electrochemical microscopy approach will be extended to other materials and reactions of interest in the CRC in the third funding period, including different reactions such as alcohol oxidation or catalysts, e.g., perovskites.
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Last update: Aug 17, 2026
