In view of continuously increasing atmospheric CO2 emissions and associated negative consequences, the thermocatalytic conversion of CO2 towards value-added products constitutes a promising starting point to mitigate the global CO2 emissions and to go one step towards a more circular economy. Ideally, the CO2 emissions are captured directly at their point sources and converted with only green hydrogen, being produced via water electrolysis using wind or solar energy, into value-added products. However, for achieving this goal, the search for the optimal catalyst constitutes a major challenge. For the rational design of improved or newly designed catalyst formulations, performing operando characterization experiments for deducing a fundamental understanding of structure-performance correlations of solid catalysts is indispensable. Inherent to such a fundamental understanding is the choice of appropriate characterization techniques of catalysts at work. This ambition also drives the continuous development of advanced characterization techniques for catalysis research. Amongst those, laboratory-based X-ray absorption spectroscopy (XAS) and especially X-ray absorption near-edge structure (XANES) analysis emerged as highly promising approach. Based on the recent developments, laboratory-based XAS presents a real alternative and complement to precious beamtime at synchrotron facilities. Especially the possible catalyst screening, being impossible at a synchrotron facility, allows for a fundamental understanding of structure-performance correlations of newly designed catalysts. Here, we highlight the new possibilities of laboratory-based XAS for advanced catalyst characterization and its great potential for the rational development of improved or new CO2 valorization catalysts. We successfully designed a setup for performing operando XANES experiments, quasi-simultaneous at multiple K edges, more specifically, operando XANES of Ni, Fe, and Cu containing mono-, bi-, and trimetallic catalysts during CO2 hydrogenation. Detailed operando XANES studies provided new insights into synergistic effects through metal alloy formation during reduction and their influence on catalytic performance in CO2 hydrogenation. The applicability of operando laboratory-based XANES experiments at multiple K edges paves the way for advanced multi-element catalyst characterization.

Advanced characterization of multi-metal CO2 hydrogenation catalysts: An operando laboratory-based X-ray absorption spectroscopy showcase

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.