From Model Systems To Real Catalysts: Bridging The Pressure And Materials Gaps

For decades a fundamental understanding of heterogeneous catalysts has been pursued for rational catalyst design using model systems under ultrahigh vacuum (UHV) conditions; however, there exist stark differences between the simplified models investigated under UHV and the industrial catalysts used at high pressures. To bridge these gaps, it becomes essential to utilize progressively more complex materials and to correlate their surface structure and activity using incrementally higher pressure techniques. In this work, both model Pt-Re catalysts and powdered metal-organic frameworks (MOFs) were studied using a suite of traditional UHV surface science techniques in addition to ambient pressure X-ray photoelectron spectroscopy (APXPS) and UHV-coupled ambient pressure cells. CO oxidation and methanol oxidation were investigated by APXPS on Pt(111), Re films on Pt(111), and on Pt−Re alloy model surfaces. Pt-Re alloy surfaces were found to dissociate oxygen more readily than Pt surfaces, and CO was found to desorb at lower temperatures from Pt−Re alloy surfaces than from Pt. Pt and Pt-Re surfaces were found to have similar product formation with Pt-Re alloys having higher activity and maintaining greater selectivity than Pt to CO2 formation. Model Pt-Re systems were also studied for methanol oxidation in a UHV-coupled microreactor where products were determined via GC-TCD, and pre- and post-reaction surfaces were characterized by XPS without exposure to air. The Pt-Re alloy surface initially showed less activity than Pt; but over extended time periods, the alloy maintained higher activity than Pt, which deactivated due to accumulation of atomic carbon. Re films were unstable since they form volatile Re2O7, but alloying Re with Pt made it less susceptible to sublimation. Water-gas shift was also performed in the microreactor on TiO2(110)-supported Pt, Re, and Pt-Re bimetallic clusters. Surface ReOx appears to block Pt active sites, but Re underneath Pt shows higher activity than Pt alone as Re modifies Pt. A separate UHV XPS-coupled high pressure cell was used to study the generation of mixed valence Cu+1/+2 sites in a powdered MOF before and after extensive heating and exposure to H2, O2, CO, and air, which corresponded to changes in the valence band, indicating tunability of the MOF’s electronic properties

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Scleroderma and related disorders: 223. Long Term Outcome in a Contemporary Systemic Sclerosis Cohort

Background: We have previously compared outcome in two groups of systemic sclerosis (SSc) patients with disease onset a decade apart and we reported data on 5 year survival and cumulative incidence of organ disease in a contemporary SSc cohort. The present study examines longer term outcome in an additional cohort of SSc followed for 10 years. Methods: We have examined patients with disease onset between years 1995 and 1999 allowing for at least 10 years of follow-up in a group that has characteristics representative for the patients we see in contemporary clinical practice. Results: Of the 398 patients included in the study, 252 (63.3%) had limited cutaneous (lc) SSc and 146 (36.7%) had diffuse cutaneous (dc) SSc. The proportion of male patients was higher among the dcSSc group (17.1% v 9.9%, p = 0.037) while the mean age of onset was significantly higher among lcSSc patients (50 ± 13 v 46 ± 13 years ± SD, p = 0.003). During a 10 year follow-up from disease onset, 45% of the dcSSc and 21% of the lcSSc subjects developed clinically significant pulmonary fibrosis, p < 0.001. Among them approximately half reached the endpoint within the first 3 years (23% of dcSSc and 10% of lcSSc) and over three quarters within the first 5 years (34% and 16% respectively). There was a similar incidence of pulmonary hypertension (PH) in the two subsets with a steady rate of increase over time. At 10 years 13% of dcSSc and 15% of lcSSc subjects had developed PH (p=0.558), with the earliest cases observed within the first 2 years of disease. Comparison between subjects who developed PH in the first and second 5 years from disease onset demonstrated no difference in demographic or clinical characteristics, but 5-year survival from PH onset was better among those who developed this complication later in their disease (49% v 24%), with a strong trend towards statistical significance (p = 0.058). Incidence of SSc renal crisis (SRC) was significantly higher among the dcSSc patients (12% v 4% in lcSSc, p = 0.002). As previously observed, the rate of development of SRC was highest in the first 3 years of disease- 10% in dcSSc and 3% in lcSSc. All incidences of clinically important cardiac disease developed in the first 5 years from disease onset (7% in dcSSc v 1% in lcSSc, p < 0.001) and remained unchanged at 10 years. As expected, 10-year survival among lcSSc subjects was significantly higher (81%) compared to that of dcSSc patients (70%, p = 0.006). Interestingly, although over the first 5 years the death rate was much higher in the dcSSc cohort (16% v 6% in lcSSc), over the following years it became very similar for both subsets (14% and 13% between years 5 and 10, and 18% and 17% between years 10 and 15 for dcSSc and lcSSc respectively). Conclusions: Even though dcSSc patients have higher incidence for most organ complications compared to lcSSc subjects, the worse survival among them is mainly due to higher early mortality rate. Mortality rate after first 5 years of disease becomes comparable in the two disease subsets. Disclosure statement: The authors have declared no conflicts of interes

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

<i>In Situ</i> Studies of Carbon Monoxide Oxidation on Platinum and Platinum–Rhenium Alloy Surfaces

CO oxidation has been investigated by near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) on Pt(111), Re films on Pt(111), and a Pt–Re alloy surface. The Pt–Re alloy surface was prepared by annealing Re films on Pt(111) to 1000 K; scanning tunneling microscopy, low energy ion scattering, and X-ray photoelectron spectroscopy studies indicate that this treatment resulted in the diffusion of Re into the Pt(111) surface. Under CO oxidation conditions of 500 mTorr O₂/50 mTorr CO, CO remains on the Pt(111) surface at 450 K, whereas CO desorbs from the Pt–Re alloy surface at lower temperatures. Furthermore, the Pt–Re alloy dissociates oxygen more readily than Pt(111) despite the fact that all of the Re atoms are initially in the subsurface region. Mass spectrometer studies show that the Pt–Re alloy, Re film on Pt, and Pt(111) all have similar activities for CO oxidation, with the Pt–Re alloy producing ∼10% more CO₂ than Pt(111). The Re film is not stable under CO oxidation conditions at temperatures ≥450 K due to the formation and subsequent sublimation of volatile Re₂O₇. However, the Pt–Re alloy surface is more resistant to oxidation and therefore also more stable against Re sublimation

Nucleation, Growth, and Adsorbate-Induced Changes in Composition for Co–Au Bimetallic Clusters on TiO₂

The nucleation, growth, and CO-induced changes in composition for Co–Au bimetallic clusters deposited on TiO₂(110) have been studied by scanning tunneling microscopy (STM), low energy ion scattering (LEIS), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. STM experiments show that the mobility of Co atoms on TiO₂(110) is significantly lower than of Au atoms; for equivalent or lower coverages of Co, the number of clusters is higher and the average cluster height is smaller than for Au deposition. Consequently, bimetallic clusters are formed by first depositing the less mobile Co atoms, followed by the addition of the more mobile Au atoms. Furthermore, the reverse deposition of Au followed by Co results in clusters of pure Co coexisting with clusters that are Au-rich. For clusters with a total coverage of 0.25 ML, the cluster density increases and average cluster height decreases as the fraction of Co is increased. Annealing to 800 K results in cluster sintering and an increase of ∼3–5 Å in average height for all compositions. LEIS experiments indicate that the surfaces of the bimetallic clusters are 80–100% Au for bulk Au fractions greater than 50%, but Co and Au coexist at the surfaces when there are not enough Au atoms available to completely cover the surfaces of the clusters. After heating to 800 K, pure Co clusters become partially encapsulated by titania, and for bimetallic clusters, the Co is selectively encapsulated at the cluster surface. The desorption of CO from the bimetallic clusters demonstrates that the presence of the CO adsorbate induces diffusion of Co to the cluster surface, but the extent of this diffusion is less than what is observed in the Ni–Au and Pt–Au systems. Density functional theory calculations confirm that for a 50% Co/50% Au bimetallic structure: the surface is predominantly Au in the absence of CO; CO induces diffusion of Co to the cluster surface; and this CO-induced diffusion is less extensive on Co–Au than on the Ni–Au and Pt–Au surfaces

<i>In Situ</i> Ambient Pressure X‑ray Photoelectron Spectroscopy Studies of Methanol Oxidation on Pt(111) and Pt–Re Alloys

For methanol oxidation reactions, Pt–Re alloy surfaces are found to have better selectivity for CO₂ production and less accumulation of surface carbon compared to pure Pt surfaces. The unique activity of the Pt–Re surface is attributed to the increased ability of Re to dissociate oxygen compared to Pt and the ability of Re to diffuse gradually to the surface under reaction conditions. In this work, the oxidation of methanol was studied by ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and mass spectrometry on Pt(111), a Pt–Re surface alloy, and a Re film on Pt(111) as well as Pt(111) and Pt–Re alloy surfaces that were preoxidized before reaction. Methanol oxidation conditions consisted of 200 mTorr of O₂/100 mTorr of methanol at temperatures ranging from 300 to 550 K. The activities of all of the surfaces studied are similar in that CO₂ and H₂O are the main oxidation products, along with formaldehyde, which is produced below 450 K. For reaction on Pt(111), there is a change in selectivity that favors CO and H₂ over CO₂ at 500 K and above. This shift in selectivity is not as pronounced on the Pt–Re alloy surface and is completely absent on the oxidized Pt–Re alloy surfaces and oxidized Re film. AP-XPS results demonstrate that Pt(111) is more susceptible to poisoning by carbonaceous surface species than any of the Re-containing surfaces. Oxygen-induced diffusion of Re to the surface is believed to occur at elevated temperatures under reaction conditions, based on the increase in the Re/Pt ratio upon heating; density function theory (DFT) calculations confirm that there is a thermodynamic driving force for Re atoms to diffuse to the surface in the presence of oxygen. Furthermore, Re diffuses to the surface when the Pt–Re alloy is exposed to O₂ at 450 K before methanol oxidation, and consequently this surface has the highest CO₂ production at temperatures below that required for Re diffusion during methanol reaction. Although the oxidized Re film also exhibits high selectivity for CO₂ production and minimal carbon deposition, this surface is unstable due to the sublimation of Re₂O₇; in contrast, the Pt–Re alloy is more resistant to Re sublimation since the majority of Re resides in the subsurface region

Active Sites in Copper-Based Metal–Organic Frameworks: Understanding Substrate Dynamics, Redox Processes, and Valence-Band Structure

We have developed an integrated approach that combines synthesis, X-ray photoelectron spectroscopy (XPS) studies, and theoretical calculations for the investigation of active unsaturated metal sites (UMS) in copper-based metal–organic frameworks (MOFs). Specifically, extensive reduction of Cu⁺² to Cu⁺¹ at the MOF metal nodes was achieved. Introduction of mixed valence copper sites resulted in significant changes in the valence band structure and an increased density of states near the Fermi edge, thereby altering the electronic properties of the copper-based framework. The development of mixed-valence MOFs also allowed tuning of selective adsorbate binding as a function of the UMS oxidation state. The presented studies could significantly impact the use of MOFs for heterogeneous catalysis and gas purification as well as foreshadow a new avenue for controlling the conductivity of typically insulating MOF materials