Resolving the Reaction Mechanism for H₂ Formation from High-Temperature Water–Gas Shift by Chromium–Iron Oxide Catalysts

The reaction mechanism of the high-temperature water–gas shift (HT-WGS) reaction catalyzed by chromium–iron oxide catalysts for H₂ production has been studied for 100 years with two reaction mechanisms proposed: redox and associative (involving surface HCOO*). Direct experimental support for either mechanism, however, is still lacking, which hinders a thorough understanding of catalytic roles of each elements and the rational design of Cr-free catalysts. The current study demonstrates, with temperature-programmed surface reaction (TPSR) spectroscopy (CO-TPSR, CO+H₂O-TPSR, and HCOOH-TPSR), for the first time that the HT-WGS reaction follows the redox mechanism and that the associative mechanism does not take place

Determining Number of Active Sites and TOF for the High-Temperature Water Gas Shift Reaction by Iron Oxide-Based Catalysts

This study demonstrates, with C¹⁶O₂/C¹⁸O₂ isotope switch and H₂-TPR experiments, for the first time that (<i>i</i>) the high-temperature water–gas shift (HT-WGS) reaction by copper–chromium-iron oxide catalysts follows a redox mechanism dominated by the surface layer, (<i>ii</i>) the number of catalytic active sites can be quantified by the isotopic switch, and (<i>iii</i>) the turnover frequency (TOF) can be determined from knowledge of the number of sites. The quantitative TOF values reveal that chromium is only a textural promoter, whereas copper is a chemical promoter

Acetic Acid Enhanced Narrow Band Imaging for the Diagnosis of Gastric Intestinal Metaplasia

<div><p>Gastric intestinal metaplasia (GIM) is a precancerous lesion of the stomach. The detection of GIM using conventional white-light endoscopy (WLE) is difficult. In this study, we determined whether acetic acid-enhanced narrow band imaging (AA-NBI) improves the detection of GIM. A consecutive cohort of 132 individuals aged 40 years or older was subjected to upper gastrointestinal endoscopy using WLE, NBI and AA-NBI. The ability of the three methods to diagnose GIM in patients was compared. Histological assessment (per-patient and per-biopsy) was used for the accuracy assessment. Sixty-six (50.0%) out of the 132 individuals examined were found to have GIM, of which 44 (66.7%) were diagnosed correctly by NBI (sensitivity 66.7% and specificity 68.2%) and 58 (87.9%) were correctly identified by AA–NBI (sensitivity 87.9% and specificity 68.2%), as compared to only 22 (33.3%) by WLE (sensitivity 33.3% and specificity 28.8%). Therefore, the sensitivity of AA–NBI in the diagnosis of GIM was significantly higher than NBI (p<0.05) and WLE (p < 0.001). Our study indicates that AA-NBI can improve the accuracy of endoscopy-targeted biopsies for GIM.</p></div

The demographics of the study samples.

<p>The demographics of the study samples.</p

Appearance of the GIM with the lens closing to the lesions.

<p>A, the lesion shows bluish-whitish areas with a regular mucosal pattern in the NBI model. B, the lesion shows whitish patches with a regular mucosal pattern in the AA-NBI model.</p

Elucidating the Reactivity and Mechanism of CO₂ Electroreduction at Highly Dispersed Cobalt Phthalocyanine

Transforming carbon dioxide to carbon monoxide with electrochemical methods allows for small-scale, modular conversion of point sources of carbon dioxide. In this work, through the preparation of a well-dispersed cobalt phthalocyanine model catalyst immobilized on carbon paper, we revealed high turnover frequencies for reducing carbon dioxide at low catalyst loadings, which are obscured at higher loadings due to aggregation. The low catalyst loadings have also enabled mechanistic studies that provide a detailed understanding of the molecular-level picture of how cobalt phthalocyanine facilitates proton and electron transfers in the rate-limiting step. We are able to tune the rate-limiting step from electron transfer to concerted proton–electron transfer, enabling higher rates of carbon dioxide reduction. Our results highlight the significance of dispersion for understanding the intrinsic catalytic performance of metal phthalocyanines for electroreduction of CO₂

Patients with histologically confirmed diagnosis of GIM.

<p>Patients with histologically confirmed diagnosis of GIM.</p

Clinical characteristics of the study samples.

<p>Clinical characteristics of the study samples.</p

Appearance of intestinal metaplasia in the antrum of the same patient under three different endoscopic models.

<p>A, Endoscopic image in WLE shows antrum mucosa is normal. B, After being switched to the NBI model, no obvious bluish-whitish areas appear. C, The whitish patches are observed after sprinkling with acetic acid in the AA-NBI model. D, Targeted biopsy shows intestinal metaplasia of the stomach.</p

Diagnostic accuracy of endoscopy in patients with GIM by WLE, NBI and AA-NBI.

<p>Diagnostic accuracy of endoscopy in patients with GIM by WLE, NBI and AA-NBI.</p