Karin Föttinger

ZUSAMMENFASSUNG: Auf Misch‐Metalloxiden basierende Hybrid‐Materialien liefern durch einen redox‐induzierten Grenzflächeneffekt eine effektive Strategie, um die katalytische Performance zu steigern. In dieser Arbeit wird ein effizienter Katalysator zur N ₂ O‐Zersetzung vorgestellt, der auf Co ₃ O ₄ ‐Spinell geträgerte RhO _x ‐ und CeO _x ‐Spezies besteht. Die Aktivitätssteigerung zu reinem Co ₃ O ₄ basiert nicht ausschließlich auf RhO _x /Co ₃ O ₄ ‐ und CeO _x /Co ₃ O ₄ ‐Grenzflächen, sondern auch vor allem auf einer einzigartigen Modulation des Co‐ und Rh‐Oxidationszustandes an einer synergierenden Rh‐O‐Co‐O‐Ce‐Grenzfläche. Dieses Zusammenspiel liefert eine gesteigerte Redox‐Flexibilität und vereinfacht die Aktivierung der Gittersauerstoffe, welches in einer eindeutigen Steigerung der N ₂ O‐Zersetzungsaktivität resultiert. Kinetische Analysen und operando ‐anregungsmodulierte Röntgenabsorptionsspektroskopie (ME‐XAS) liefern direkte reaktionsmechanistische Beweise für den Ablauf der N ₂ O‐Zersetzung über einen multi‐positionellen, kooperativen Mars‐van‐Krevelen‐Mechanismus. Darin agiert Co ₃ O ₄ ‐CeO ₂ als Sauerstoffreservoir, welches den Redox‐Zyklus der RhO _x ‐Species ermöglicht. Diese Studie beleuchtet die Fähigkeit der Misch‐Metalloxid‐Katalysatoren Grenzflächeneffekte auszunutzen, um eine Aktivitätssteigerung in Redox‐Reaktionen zu erwirken. Ebenfalls liefert sie eine Motivation zur Optimierung von Metalloxid‐Metalloxid‐Katalysatoren durch operando ‐Spektroskopie.

Hybrid materials based upon mixed metal oxides provide an effective strategy to boost catalytic performance through redox‐induced interfacial engineering. Herein, we present an efficient catalyst toward N ₂ O decomposition containing short‐range ordered RhO _x and CeO _x species anchored to the Co ₃ O ₄ spinel. The activity enhancement relative to Co ₃ O ₄ is non‐additive with respect to the RhO _x /Co ₃ O ₄ and CeO _x /Co ₃ O ₄ interfaces and is uniquely linked to the modulation of the Co and Rh oxidation states at a synergistic Rh–O–Co–O–Ce interface. This ensemble provides increased redox flexibility and facilitated lattice oxygen activation, resulting in markedly enhanced N ₂ O decomposition. Kinetic analysis and operando modulated excitation x‐ray absorption spectroscopy (ME‐XAS) provide direct mechanistic evidence that N ₂ O decomposition proceeds via a multi‐site, cooperative Mars‐van Krevelen pathway, in which Co ₃ O ₄ –CeO ₂ acts as an oxygen reservoir enabling the redox cycling of RhO _x species. This study highlights the ability of mixed metal oxide catalysts to exploit interfacial effects to achieve improved activity in redox‐mediated reactions and offers a rationale for the engineering of metal oxide–metal oxide catalysts guided by operando spectroscopy.

With the ongoing interest in developing more stable and versatile catalysts for CO ₂ hydrogenation to methanol, molybdenum sulfide (MoS ₂ ) has been recently proposed as an alternative material.

Electrochemical CO2 reduction (ECR) to formic acid is widely proposed as a carbon utilization strategy, yet the environmental implications of both material selection and process parameters remain poorly quantified. A cradle-to-gate life cycle assessment was conducted evaluating four reported high-performance electrocatalysts (SnS2, In2O3, Bi0.6Cu0.4, and In2S3/In2O3) against conventional methyl formate hydrolysis for the production of 1 kg of formic acid. We found that, under grid electricity, all ECR scenarios impose substantially greater environmental burdens than the conventional process, with climate change impacts ranging from 4.476 to 5.934 kg CO2-eq kg-1 FA. Power consumption during water electrolysis constitutes the dominant impact driver, though synthesis-stage energy demands contribute disproportionately for SnS2 (66% of total electricity). Despite achieving the highest Faradaic efficiency (~98%), Bi0.6Cu0.4 exhibits a mineral resource depletion impact 23-fold above the conventional baseline, revealing a fundamental tension between electrochemical selectivity and material resource sustainability. Substitution with hydropower or wind electricity reduces GWP by 43–63%, yet material resource and ecotoxicity burdens remain structurally decoupled from electricity source. Water use is the sole category where all ECR scenarios outperform conventional production, with freshwater reductions of 84–94%. Therefore, sustainable deployment of ECR requires coordinated advancement across grid decarbonization, synthesis redesign, and catalyst material optimization rather than electrochemical performance improvement alone. Extending beyond electrochemical CO₂ reduction (ECR), this model can be adapted and applied to thermal and photocatalytic processes for converting CO₂ into a range of products.

The N species on CN _x modified the electronic and topological structure of Pt, improving the catalytic properties of the Pt/CN _x catalyst in evolving hydrogen from NH ₃ BH ₃ .

Epimerization of d -glucose into d -mannose catalyzed by tin-organic frameworks was performed. Separation of the obtained mixture of d -glucose and d -mannose using crystallization and adsorption was examined.