CO and O2 Interaction with Kinked Pt Surfaces.

We investigate the chemical interaction of carbon monoxide (CO) and oxygen (O2) with kink atoms on steps of platinum crystal surfaces using a specially designed Pt curved sample. We aim at describing the fundamental stages of the CO oxidation reaction, i.e., CO-covered/poisoned stage and O-covered/active stage, at the poorly known kinked Pt facets by probing CO uptake/saturation and O2 saturation, respectively. Based on the systematic analysis that the curved surface allows, and using high-resolution X-ray photoemission, a diversity of terrace and step/kink species are straightforwardly identified and accurately quantified, defining a smooth structural and chemical variation across different crystal planes. In the CO-saturated case, we observe a preferential adsorption at step edges, where the CO coverage reaches a CO molecule per step Pt atom, significantly higher than their close-packed analogous steps with straight terrace termination. For the O-saturated surface, a significantly higher O coverage is observed in kinked planes compared to the Pt(111) surface. While the strong adsorption of CO at the kinked edges points toward a higher ignition temperature of the CO oxidation at kinks as compared to terraces, the large O coverage at steps may lead to an increased reactivity of kinked surfaces during the active stage of the CO oxidation.

Multi-spectroscopic study of electrochemically-formed oxide-derived gold electrodes.

Oxide-derived metals are produced by reducing an oxide precursor. These materials, including gold, have shown improved catalytic performance over many native metals. The origin of this improvement for gold is not yet understood. In this study, operando non-resonant sum frequency generation (SFG) and ex situ high-pressure X-ray photoelectron spectroscopy (HP-XPS) have been employed to investigate electrochemically-formed oxide-derived gold (OD-Au) from polycrystalline gold surfaces. A range of different oxidizing conditions were used to form OD-Au in acidic aqueous medium (H3PO4, pH = 1). Our electrochemical data after OD-Au is generated suggest that the surface is metallic gold, however SFG signal variations indicate the presence of subsurface gold oxide remnants between the metallic gold surface layer and bulk gold. The HP-XPS results suggest that this subsurface gold oxide could be in the form of Au2O3 or Au(OH)3. Furthermore, the SFG measurements show that with reducing electrochemical treatments the original gold metallic state can be restored, meaning the subsurface gold oxide is released. This work demonstrates that remnants of gold oxide persist beneath the topmost gold layer when the OD-Au is created, potentially facilitating the understanding of the improved catalytic properties of OD-Au.

Operando probing of the surface chemistry during the Haber-Bosch process.

The large-scale conversion of N2 and H2 into NH3 (refs. 1,2) over Fe and Ru catalysts3 for fertilizer production occurs through the Haber-Bosch process, which has been considered the most important scientific invention of the twentieth century4. The active component of the catalyst enabling the conversion was variously considered to be the oxide5, nitride2, metallic phase or surface nitride6, and the rate-limiting step has been associated with N2 dissociation7-9, reaction of the adsorbed nitrogen10 and also NH3 desorption11. 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 calculations12. Here we use X-ray photoelectron spectroscopy-capable of revealing the chemical state of catalytic surfaces and recently adapted to operando investigations13 of methanol14 and Fischer-Tropsch synthesis15-to determine the surface composition of Fe and Ru catalysts during NH3 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 (NHx) coverages on the stepped surfaces. These observations indicate that the rate-limiting step on Ru is always N2 dissociation. On Fe catalysts, by contrast and as predicted by theory16, hydrogenation of adsorbed N atoms is less efficient to the extent that the rate-limiting step switches following temperature lowering from N2 dissociation to the hydrogenation of surface species.

Demonstrating Pressure Jumping as a Tool to Address the Pressure Gap in High Pressure Photoelectron Spectroscopy of CO and CO2 Hydrogenation on Rh(211).

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 CO2 and the CO hydrogenation reaction over Rh(211). In the CO2 hydrogenation reaction, the remnant surface of a 2 bar pressure shows an adsorbate distribution which favors chemisorbed CHx 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 CHx accumulated faster during the 275 mbar low pressure regime, and different hypotheses are presented regarding this observation.

Tratamiento percutáneo del cáncer infiltrante de mama en estado clínico I/II mediante crioablación en pacientes sin indicación de cirugía axilar / Percutaneous cryoablation of clinical stage I/II breast cancer in patients without indication for axillary surgery

Objetivo: revisar la eficacia del tratamiento percutáneo del cáncer infiltrante de mama (CM) mediante crioablación guiada con ecografía en pacientes con estadio clínico I/II en las que se desestima la cirugía axilar. Métodos: se recogieron de nuestros archivos las pacientes con CM en estadio clínico I/II que fueron tratadas mediante crioablación guiada con ecografía en las que se desestimó la cirugía axilar. Se seleccionaron las pacientes que tuvieron un seguimiento mínimo de 12 meses. Las revisiones fueron ecográficas: la primera entre 1 y 2 meses (para valorar lesiones residuales por tratamiento incompleto) y posteriormente semestrales (para valorar las recidivas). Las lesiones residuales y las recidivas se confirmaron con BAG y en todos los casos se valoró el tratamiento con nueva crioablación (de rescate). Se analizó la eficacia del procedimiento en función del control local en la mama. Resultados: desde marzo de 2019 hasta septiembre de 2022 fueron tratadas mediante crioablación guiada con ecografía 84 pacientes con 92 CM en estadio clínico I/II en las que la cirugía axilar fue desestimada. Se estudiaron retrospectivamente las 43 pacientes (58-96 años, media 83, DE ±7,64) con 48 CM (entre 5 y 60 mm, media 17, DE ±13,75) que tuvieron un seguimiento mínimo de 12 meses (entre 12 y 40 meses, media 20). Hubo 2 pacientes con tratamiento incompleto en la primera ecografía y 5 pacientes recidivaron (entre 9 y 27 meses, media 17). Todas se trataron con crioablaciones de rescate. El control local a los 12 meses fue del 90,5% (probabilidad 0,905 error estándar 0,045) y en el 95% de las pacientes (41/43) se consiguió controlar localmente el CM. Fallecieron 6 pacientes, 3 por evolución del CM y 3 por otras causas. Todos los procedimientos fueron bien tolerados y no hubo complicaciones graves. (AU)

Objective: To review the efficacy of percutaneous treatment of infiltrating breast cancer (BC) by ultrasound-guided cryoablation in patients with clinical stage I/II without indication for axillary surgery Methods: Patients with clinical stage I/II BC who were treated by ultrasound-guided cryoablation in whom axillary surgery was ruled out were collected from our files. Patients who had a minimum follow-up of 12 months were selected. The ultrasound follow up were: the first between 1-2 months (to assess residual lesions due to incomplete treatment) and subsequently every six months (to assess recurrences). Residual lesions and recurrences were confirmed with CNB and in all cases treatment with new (salvage) cryoablation was considered. The efficacy of the procedure was assessed on local control in the breast. Results: Between March 2019 and September 2022, 84 patients with 92 BC in clinical stage I/II were treated with ultrasound-guided cryoablation without indication for axillary surgery. The inclusion criteria of the retrospective study were met by 43 patients (58-96 years, mean 83, SD ±7,64) with 48 BC (between 5-60mm, mean 17, SD ±13,75) who were reviewed during a mean period of 20 months (between 12-40 months). There were two patients with incomplete treatment at the first ultrasound and five patients relapsed (between 9-27 months, mean 17). All were treated with salvage cryoablation. Local control at 12 months was 90.5% (probability 0.905 standard error 0.045) and in 95% of patients (41/43) the BC was locally controlled. Six patients died, three due to progression of the BC and three due to other causes. All procedures were well tolerated and there were no serious complications. (AU)

Structure Matters: Asymmetric CO Oxidation at Rh Steps with Different Atomic Packing.

Curved crystals are a simple but powerful approach to bridge the gap between single crystal surfaces and nanoparticle catalysts, by allowing a rational assessment of the role of active step sites in gas-surface reactions. Using a curved Rh(111) crystal, here, we investigate the effect of A-type (square geometry) and B-type (triangular geometry) atomic packing of steps on the catalytic CO oxidation on Rh at millibar pressures. Imaging the crystal during reaction ignition with laser-induced CO2 fluorescence demonstrates a two-step process, where B-steps ignite at lower temperature than A-steps. Such fundamental dissimilarity is explained in ambient pressure X-ray photoemission (AP-XPS) experiments, which reveal partial CO desorption and oxygen buildup only at B-steps. AP-XPS also proves that A-B step asymmetries extend to the active stage: at A-steps, low-active O-Rh-O trilayers buildup immediately after ignition, while highly active chemisorbed O is the dominant species on B-type steps. We conclude that B-steps are more efficient than A-steps for the CO oxidation.

Reduced Carbon Monoxide Saturation Coverage on Vicinal Palladium Surfaces: the Importance of the Adsorption Site.

Steps at metal surfaces may influence energetics and kinetics of catalytic reactions in unexpected ways. Here, we report a significant reduction of the CO saturation coverage in Pd vicinal surfaces, which in turn is relevant for the light-off of the CO oxidation reaction. The study is based on a systematic investigation of CO adsorption on vicinal Pd(111) surfaces making use of a curved Pd crystal. A combined X-ray Photoelectron Spectroscopy and DFT analysis allows us to demonstrate that an entire row of atomic sites under Pd steps remains free of CO upon saturation at 300 K, leading to a step-density-dependent reduction of CO coverage that correlates with the observed decrease of the light-off temperature during CO oxidation in vicinal Pd surfaces.

Catalytic Oxidation of CO on a Curved Pt(111) Surface: Simultaneous Ignition at All Facets through a Transient CO-O Complex*.

The catalytic oxidation of CO on transition metals, such as Pt, is commonly viewed as a sharp transition from the CO-inhibited surface to the active metal, covered with O. However, we find that minor amounts of O are present in the CO-poisoned layer that explain why, surprisingly, CO desorbs at stepped and flat Pt crystal planes at once, regardless of the reaction conditions. Using near-ambient pressure X-ray photoemission and a curved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. Analysis of C and O core levels across the curved crystal reveals that, right before light-off, subsurface O builds up within (111) terraces. This is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces: a CO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps, leading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature.