CuGaO2 Delafossite as a High-Surface Area Model Catalyst for Cu+- Activated Reactions

ESTEBAN FORNERO; GUSTAVO E. MURGIDA; MARTA BOSCO; JUAN C. HERNÁNDEZ GARRIDO; ALEJO AGUIRRE; FLORENCIA CALAZA; STACCHIOLA, DARIO; M. VERÓNICA GANDUGLIA-PIROVANO; ADRIAN L. BONIVARDI

Zaragoza

Workshop; IUVSTA-ZCAM METAL-OXIDE ULTRATHIN FILMS AND NANOSTRUCTURES: EXPERIMENT MEETS THEORY; 2023

Copper is one of the goldilocks metals in catalysis. Deciphering the local atomic environmentand oxidation state of active centers in supported copper catalysts, as well as the design ofmaterials to control their stability under reaction conditions remains a great challenge today.In general, it has been highlighted that copper species in the intermediate oxidation state 1+(Cu1+) play a key and beneficial role in a wide variety of important heterogeneous catalyticreactions, such as the synthesis of methanol [1,2], water gas shift reaction [3,4], reformingreactions [5], electrochemical reduction of CO2 [6], dehydrogenation and hydrogenationreactions [7,8], epoxidation of propylene [9] and CO oxidation [10], among others.In this work, well-defined copper and gallium delafossite (CuGaO2, Cu1+ and Ga3+) wassynthesized to maximize the number of stable Cu1+ sites on a high surface area model-catalyst.An exhaustive multimodal characterization was carried out by combining high resolutiontransmission electron microscopy (HR-TEM), X-ray diffraction (XRD), ambient pressure Xrayphotoelectron spectroscopy (AP-XPS), operando IR spectroscopy, and density functionaltheory (DFT) calculations in order to determine the morphology and nature of active surfacesites on CuGaO2. We show here how CuGaO2 in the form of porous nanoplates, mainlyexposing (110) facets with Cu1+ and Ga3+ cations in well-defined surface positions, can be usedas a model to explore the activity and stability of Cu1+-activated reactions.Our results also show that the delafossite structure is preserved after calcination or reductionpretreatments (in pure O2 or H2, respectively), and has the potential to develop new technicalcatalysts. Extensive reduction of the mixed-oxide leads to a stable catalyst with higher activityfor CO oxidation, as a result of the formation of geminal dicarbonyl species on Cu , with 0