Investigation of Active Catalysts at Work

Abstract

Conspectus Even after being in business for at least the last 100 years, research into the field of (heterogeneous) catalysis is still vibrant, both in academia and in industry. One of the reasons for this is that around 90% of all chemicals and materials used in everyday life are produced employing catalysis. In 2020, the global catalyst market size reached $35 billion, and it is still steadily increasing every year. Additionally, catalysts will be the driving force behind the transition toward sustainable energy. However, even after having been investigated for 100 years, we still have not reached the holy grail of developing catalysts from rational design instead of from trial-and-error. There are two main reasons for this, indicated by the two so-called “gaps” between (academic) research and actual catalysis. The first one is the “pressure gap”, indicating the 13 orders of magnitude difference in pressure between the ultrahigh vacuum lab conditions and the atmospheric pressures (and higher) of industrial catalysis. The second one is the “materials gap”, indicating the difference in complexity between single-crystal model catalysts of academic research and the real catalysts, consisting of metallic nanoparticles on supports, promoters, fillers, and binders. Although over the past decades significant efforts have been made in closing these gaps, many steps still have to be taken. In this Account, I will discuss the steps we have taken at Leiden University to further our fundamental understanding of heterogeneous catalysis at the (near-)atomic scale. I will focus on bridging the pressure gap, though we are also working on closing the materials gap. Over the past years, we developed state-of-the-art equipment that is able to investigate the (near-)atomic-scale structure of the catalyst surface during the chemical reaction using several surface-science-based techniques such as scanning tunneling microscopy, atomic force microscopy, optical microscopy, and X-ray-based techniques (surface X-ray diffraction, grazing-incidence small-angle X-ray scattering, and X-ray reflectivity, in collaboration with ESRF). Simultaneously with imaging the surface, we can investigate the catalyst’s performance via mass spectrometry, enabling us to link changes in the catalyst structure to its activity, selectivity, or stability. Although we are currently investigating many industrially relevant catalytic systems, I will here focus the discussion on the oxidation of platinum during, for example, CO and NO oxidation, the NO reduction reaction on platinum, and the growth of graphene on liquid (molten) copper. I will show that to be able to obtain the full picture of heterogeneous catalysis, the ability to investigate the catalyst at the (near-)atomic scale during the chemical reaction is a must.

Tracking the Oxygen Dynamics of Solid–Liquid Electrochemical Interfaces by Correlative In Situ Synchrotron Spectroscopies

“…8,17 To gain a full picture of the catalytic dynamics, the evolution of both surface structures and reactive intermediates over the solid−liquid interface of electrodes is recommended to be concurrently monitored, but it faces a great challenge because of the complication of the electrode surface and limitation of effective detection technologies in aqueous environments. 14,18 The worldwide blossoming of synchrotron radiation (SR) facilities provides a promising and high-brilliance light source to rapidly develop SR-based spectroscopic technologies toward surficial/interfacial detection in aqueous conditions. 19−21 In particular, SR-based X-ray absorption fine structure spectroscopy (SR-XAFS), which has element specificity, high local structure sensitivity, and a strong penetration capability in aqueous solutions, is a very powerful tool to promptly probe the structural evolution of active metal centers in electrocatalysts under working conditions.…”

“…During oxygen electrocatalysis, the surface rearrangement of electrocatalysts has been commonly predicted in theoretical calculations and evidently observed in experiments. − Accompanied by surface reconstruction, a series of oxo intermediates, such as *OH, *O, *OOH, etc., successively appears over the evolved active sites of electrocatalysts during the catalytic process. , To gain a full picture of the catalytic dynamics, the evolution of both surface structures and reactive intermediates over the solid–liquid interface of electrodes is recommended to be concurrently monitored, but it faces a great challenge because of the complication of the electrode surface and limitation of effective detection technologies in aqueous environments. , …”

On-Surface Synthesis toward Two-Dimensional Polymers

“…However, all these characterizations are performed before and after the growth of material. Thus, in operando STM and time-resolved spectroscopy are invaluable extensions …”

“…Thus, in operando STM and timeresolved spectroscopy are invaluable extensions. 175 Ullmann coupling of halogenated precursors on coinage metals is more favorable for the on-surface-assisted C−C coupling reactions. However, the generation of byproducts, polymerization, competition with halogen bonding, 176 along with the intermediate compounds and polymer architectures 177 make the surface reaction complicated, but it may lead to novel structures via kinetic control.…”

Obtención de arreglos regulares metálicos sobre superficies de sistemas nanopartícula-proteína y su aplicación en catálisis

“…La comercialización de catalizadores a escala global ha crecido inmensamente en cortos períodos de tiempo, en 1998 involucraba 9,3 billones de dólares mientras que en 2003 el monto aumentó a 12 billones de dólares [Catalyst Business, 2004]. Recientemente, en 2020 dicha cifra escaló a los 35 billones de dólares anuales [Groot, 2021]. Porcentualmente, los catalizadores heterogéneos representan un 80% del mercado catalítico, los homogéneos participan en un 17% y los enzimáticos en un 3% aproximadamente [Bravo-Suárez et al, 2013].…”