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Operando probing by x-ray photoelectron spectroscopy (XPS) of certain hydrogenation reactions are often limited by the scattering of photoelectrons in the gas phase. This work describes a method designed to partially circumvent this so called pressure gap. By performing a rapid switch from a high pressure (where acquisition is impossible) to a lower pressure we can for a short while probe a "remnant" of the high pressure surface as well as the time dynamics during the re-equilibration to the new pressure. This methodology is demonstrated using the CO 2 and the CO hydrogenation reaction over Rh(211). In the CO 2 hydrogenation reaction, the remnant surface of a 2 bar pressure shows an adsorbate distribution which favors chemisorbed CH x adsorbates over chemisorbed CO. This contrasts against previous static operando spectra acquired at lower pressures. Furthermore, the pressure jumping method yields a faster acquisition and more detailed spectra than static operando measurements above 1 bar. In the CO hydrogenation reaction, we observe that CH x accumulated faster during the 275 mbar low pressure regime, and different hypotheses are presented regarding this observation., (© 2023 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

The large-scale conversion of N 2 and H 2 into NH 3 (refs.  1,2 ) over Fe and Ru catalysts 3 for fertilizer production occurs through the Haber-Bosch process, which has been considered the most important scientific invention of the twentieth century 4 . The active component of the catalyst enabling the conversion was variously considered to be the oxide 5 , nitride 2 , metallic phase or surface nitride 6 , and the rate-limiting step has been associated with N 2 dissociation 7-9 , reaction of the adsorbed nitrogen 10 and also NH 3 desorption 11 . This range of views reflects that the Haber-Bosch process operates at high temperatures and pressures, whereas surface-sensitive techniques that might differentiate between different mechanistic proposals require vacuum conditions. Mechanistic studies have accordingly long been limited to theoretical calculations 12 . Here we use X-ray photoelectron spectroscopy-capable of revealing the chemical state of catalytic surfaces and recently adapted to operando investigations 13 of methanol 14 and Fischer-Tropsch synthesis 15 -to determine the surface composition of Fe and Ru catalysts during NH 3 production at pressures up to 1 bar and temperatures as high as 723 K. We find that, although flat and stepped Fe surfaces and Ru single-crystal surfaces all remain metallic, the latter are almost adsorbate free, whereas Fe catalysts retain a small amount of adsorbed N and develop at lower temperatures high amine (NH x ) coverages on the stepped surfaces. These observations indicate that the rate-limiting step on Ru is always N 2 dissociation. On Fe catalysts, by contrast and as predicted by theory 16 , hydrogenation of adsorbed N atoms is less efficient to the extent that the rate-limiting step switches following temperature lowering from N 2 dissociation to the hydrogenation of surface species., (© 2024. The Author(s).)

Carbide formation on iron-based catalysts is an integral and, arguably, the most important part of the Fischer-Tropsch synthesis process, converting CO and H 2 into synthetic fuels and numerous valuable chemicals. Here, we report an in situ surface-sensitive study of the effect of pressure, temperature, time, and gas feed composition on the growth dynamics of two distinct iron-carbon phases with the octahedral and trigonal prismatic coordination of carbon sites on an Fe(110) single crystal acting as a model catalyst. Using a combination of state-of-the-art X-ray photoelectron spectroscopy at an unprecedentedly high pressure, high-energy surface X-ray diffraction, mass spectrometry, and theoretical calculations, we reveal the details of iron surface carburization and product formation under semirealistic conditions. We provide a detailed insight into the state of the catalyst's surface in relation to the reaction., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO 2 /CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO 2 /CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO 2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO 2 methanol synthesis.

The CO hydrogenation reaction over the Rh(111) and (211) surfaces has been investigated operando by X-ray photoelectron spectroscopy at a pressure of 150 mbar. Observations of the resting state of the catalyst give mechanistic insight into the selectivity of Rh for generating ethanol from CO hydrogenation. This study shows that the Rh(111) surface does not dissociate all CO molecules before hydrogenation of the O and C atoms, which allows methoxy and other both oxygenated and hydrogenated species to be visible in the photoelectron spectra.

Subsurface oxygen has been proposed to be crucial in oxide-derived copper (OD-Cu) electrocatalysts for enhancing the binding of CO intermediates during CO 2 reduction reaction (CO 2 RR). However, the presence of such oxygen species under reductive conditions still remains debated. In this work, the existence of subsurface oxygen is validated by grazing incident hard X-ray photoelectron spectroscopy, where OD-Cu was prepared by reduction of Cu oxide with H 2 without exposing to air. The results suggest two types of subsurface oxygen embedded between the fully reduced metallic surface and the Cu 2 O buried beneath: (i) oxygen staying at lattice defects and/or vacancies in the surface-most region and (ii) interstitial oxygen intercalated in metal structure. This study adds convincing support to the presence of subsurface oxygen in OD-Cu, which previously has been suggested to play an important role to mitigate the σ-repulsion of Cu for CO intermediates in CO 2 RR., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Heterogeneous catalyst surfaces are dynamic entities that respond rapidly to changes in their local gas environment, and the dynamics of the response is a decisive factor for the catalysts' action and activity. Few probes are able to map catalyst structure and local gas environment simultaneously under reaction conditions at the timescales of the dynamic changes. Here we use the CO oxidation reaction and a Pd(100) model catalyst to demonstrate how such studies can be performed by time-resolved ambient pressure photoelectron spectroscopy. Central elements of the method are cyclic gas pulsing and software-based event-averaging by image recognition of spectral features. A key finding is that at 3.2 mbar total pressure a metallic, predominantly CO-covered metallic surface turns highly active for a few seconds once the O 2 :CO ratio becomes high enough to lift the CO poisoning effect before mass transport limitations triggers formation of a √5 oxide., (© 2021. The Author(s).)

Performing fundamental operando catalysis studies under realistic conditions is a key to further develop and increase the efficiency of industrial catalysts. Operando X-ray photoelectron spectroscopy (XPS) experiments have been limited to pressures, and the relevance for industrial applications has been questioned. Herein, we report on the CO oxidation experiment on Pd(100) performed at a total pressure of 1 bar using XPS. We investigate the light-off regime and the surface chemical composition at the atomistic level in the highly active phase. Furthermore, the observed gas-phase photoemission peaks of CO 2 , CO, and O 2 indicate that the kinetics of the reaction during the light-off regime can be followed operando , and by studying the reaction rate of the reaction, the activation energy is calculated. The reaction was preceded by an in situ oxidation study in 7% O 2 in He and a total pressure of 70 mbar to confirm the surface sensitivity and assignment of the oxygen-induced photoemission peaks. However, oxygen-induced photoemission peaks were not observed during the reaction studies, but instead, a metallic Pd phase is present in the highly active regime under the conditions applied. The novel XPS setup utilizes hard X-rays to enable high-pressure studies, combined with a grazing incident angle to increase the surface sensitivity of the measurement. Our findings demonstrate the possibilities of achieving chemical information of the catalyst, operando , on an atomistic level, under industrially relevant conditions., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Using grazing incidence X-rays and X-ray photoelectron spectroscopy during the mass transfer limited catalytic oxidation of CO, the long-range surface structure of Pd(100) was investigated. Under the reaction conditions of 50:4 O 2 to CO, 300 mbar pressure, and temperatures between 200 and 450 °C, the surface structure resulting from oxidation and the subsequent oxide reduction was elucidated. The reduction cycle was halted, and while under reaction conditions, angle-dependent X-ray photoelectron spectroscopy close to the critical angle of Pd and modeling of the data was performed. Two proposed models for the system were compared. The suggestion with the metallic islands formed on top of the oxide island was shown to be consistent with the data.

We present a new method to maintain constant gas pressure over a sample during in situ measurements. The example shown here is a differentially pumped high-pressure X-ray photoelectron spectroscopy system, but this technique could be applied to many in situ instruments. By using the pressure of the differential stage as a feedback source to change the sample position, a new level of consistency has been achieved. Depending on the absolute value of the sample-to-aperture distance, this technique allows one to maintain the distance within several hundred nanometers, which is below the limit of typical optical microscopy systems. We show that this method is well suited to compensate for thermal drift. Thus, X-ray photoelectron spectroscopy data can be acquired continuously while the sample is heated and maintaining constant pressure over the sample. By implementing a precise manipulator feedback system, pressure variations of less than 5% were reached while the temperature was varied by 400 ℃. The system is also shown to be highly stable under significant changes in gas flow. After changing the flow by a factor of two, the pressure returned to the set value within 60 s.

This article revisits the notorious trial of William Windham, a wealthy young man accused of lunacy. The trial in 1861-2 saw the country's foremost experts on psychological medicine very publicly debate the concepts, symptoms and diagnosis of insanity. I begin by surveying the trial and the testimonies of medical experts. Their disparate assessments of Windham evoked heated reactions in the press and Parliament; these reactions are the focus of the second section. I then proceed to examine criticism of psychiatry in the newspapers more generally in the 1860s, outlining the political resistance to psychiatry and the responses of some leading psychiatrists. In conclusion, I consider what this says about the politics of medicalization at the time.

Interest in the political relevance of the emotions is growing rapidly. In light of this, Hannah Arendt's claim that the emotions are apolitical has come under renewed fire. But many critics have misunderstood her views on the relationship between individuals, emotions and the political. This paper addresses this issue by reconstructing the conceptual framework through which Arendt understands the emotions. Arendt often describes the heart - where the emotions reside - as a place of darkness. I begin by tracing this metaphor through her work to demonstrate that it is meant to convey the inherently uncertain nature of emotions rather than a devaluation of them. I proceed to challenge the notion that Arendt adopts the Enlightenment dichotomy between reason and emotion. In fact, she rejects both as a basis for politics. However, she does identify some constructive roles for the emotions. I argue that fear is intrinsically connected to courage - the principal political virtue - in Arendt's philosophy. In light of my discussion, I then reinterpret the role of compassion and pity in On Revolution , concluding that Arendt's insights can help us avoid the potential pitfalls of the contemporary project to recuperate the emotions in politics., Competing Interests: Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

This paper illustrates how concepts of mental disorder have been deployed to medicalize negative emotions and, thereby, weaken the political agency of some individuals. First, I theorise the link between political agency and emotions, arguing that effective political action entails the transformation of emotions into public issues. Using the British referendum on membership in the EU as a case study, I then examine how medically loaded terms and rhetoric were used to describe suffering after the vote. Finally, I argue that this generated conditions that interrupted or even reversed the transformation of subjective experiences into politically meaningful issues.