Tunable nano-distribution of Pt on TiO2 nanotubes by atomic compression control for high-efficient oxygen reduction reaction

Achieving cost-competitive catalysts with low Pt utilization and improving the durability caused by the corrosion of supports in the catalysts must be solved for the high activity in the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Here, we show an innovative technique to synthesize unique nanotube supports for the ORR catalysts based on the combination of experimental and theoretical studies. The method precisely controls the atomic morphology of TiO2 nanotubes by a small amount of atomic substitution, maximizing their efficiency as catalyst supports. The spontaneous change in the size and dispersibility of the Pt nanoparticles appears by only small lattice contraction on the metal-doped TiO2 (M-TiO2) nanotubes. To study this phenomenon, various dopants such as V, Nb, and Cr were added to the M-TiO2 nanotubes. The compression arising out of each metal-support interaction resulted in the diverse shape of the nanoparticles on similar supports, which is revealed based on the X-ray absorption fine structure (XAFS) and the density-functional-theory (DFT) calculations. Based on a comprehensive understanding of inter-and intracrystal interactions in the small substitution doping process, we can control the size and dispersibility of the Pt nanoparticles, catalytic activity, and durability of catalysts for ORR.11Nsciescopu

Engineering electrocatalyst nanosurfaces to enrich the activity by inducing lattice strain

Electrocatalysis undeniably offers noteworthy improvements to future energy conversion and storage technologies, such as fuel cells, water electrolyzers, and metal-air batteries. The molecular interaction between catalytic surfaces and chemical reactants produces a trade-off between catalyst activity and effectiveness, and hence requires optimization. When enhancing electrocatalysis, atomic surface structure tuning is of primary importance in simultaneously meeting demands for electrocatalytic activity and stability. The impact of lattice strain on catalytic activity tuning is experimentally revealed in de-alloyed bimetallic nanoparticles, in which surface distortion makes essential contributions to the activities of state-of-the-art electrocatalysts that vary over distinct sizes, surface defect concentrations, shapes, and atomic compositions under the studied environments. Further, metal-rich shells show compressive strain in core-shell catalyst nanoparticles, yielding shifts in metal electronic band structure features, weakened chemisorption of oxygenated species, and changes in the mechanisms governing catalyst activity. Our study evaluates the practical and fundamental effects of surface distortion and defects on interfacial electrocatalysis, namely in the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). This is accomplished via an understanding of strain from theory, establishing reactivity-strain relationships that inform the tuning and enhancement of electrocatalytic activity and stability.11Nsciescopu

Effective Screening Route for Highly Active and Selective Metal−Nitrogen‐Doped Carbon Catalysts in CO2 Electrochemical Reduction

To identify high-efficiency metal—nitrogen-doped (M—N—C) electrocatalysts for the electrochemical CO2-to-CO reduction reaction (CO2RR), a method that uses density functional theory calculation is presented to evaluate their selectivity, activity, and structural stability. Twenty-three M—N4—C catalysts are evaluated, and three of them (M = Fe, Co, or Ni) are identified as promising candidates. They are synthesized and tested as proof-of-concept catalysts for CO2-to-CO conversion. Different key descriptors, including the maximum reaction energy, differences of the *H and *CO binding energy (ΔG*H−ΔG*CO), and *CO desorption energy (ΔG*CO→CO(g)), are used to clarify the reaction mechanism. These computational descriptors effectively predict the experimental observations in the entire range of electrochemical potential. The findings provide a guideline for rational design of heterogeneous CO2RR electrocatalysts.11Nsciescopu

Role of invasive mediastinal nodal staging in survival outcomes of patients with non-small cell lung cancer and without radiologic lymph node metastasis: a retrospective cohort studyResearch in context

Summary: Background: Lung cancer diagnostic guidelines advocate for invasive mediastinal nodal staging (IMNS), but the survival benefits of this approach in patients with non-small cell lung cancer (NSCLC) without radiologic evidence of lymph node metastasis (rN0) remain uncertain. We aimed to investigate the impact of IMNS in patients with rN0 NSCLC by comparing the long-term survival between patients who underwent IMNS and those who did not (non-IMNS). Methods: In this retrospective cohort study, we included patients with NSCLC but without radiologic evidence of lymph node metastasis from the Registry for Thoracic Cancer Surgery and the clinical data warehouse at the Samsung Medical Centre, Republic of Korea between January 2, 2008 and December 31, 2016. We compared the 5-year overall survival (OS) rate as the primary outcome after propensity score matching between the IMNS and non-IMNS groups. The age, sex, performance statue, tumor size, centrality, solidity, lung function, FDG uptake in PET-CT, and histological examination of the tumor before surgery were matched. Findings: A total of 4545 patients (887 in the IMNS group and 3658 in the non-IMNS group) who received curative treatment for NSCLC were included in this study. By the mediastinal node dissection, the overall incidence of unforeseen mediastinal node metastasis (N2) was 7.2% (317/4378 patients). Despite the IMNS, 67% of pathological N2 was missed (61/91 patients with unforeseen N2). Based on propensity score matching, 866 patients each for the IMNS and non-IMNS groups were assigned. There was no significant difference in 5-year OS and recurrence-free survival (RFS) between two groups: 5-year OS was 73.9% (95% confidence interval, CI: 71%–77%) for IMNS and 71.7% (95% CI: 68.6%–74.9%; p = 0.23), for non-IMNS (hazard ratio, HR 0.90, 95% CI: 0.77–1.07), while 5-year RFS was 64.7% (95% CI: 61.5%–68.2%) and 67.5% (95% CI: 64.3%–70.9%; p = 0.35 (HR 1.08, 95% CI: 0.92–1.27), respectively. Moreover, the timing and locations of recurrence were similar in both groups. Interpretation: IMNS might not be required before surgery for patients with NSCLC without LN suspicious of metastasis. Further randomised trials are required to validate the findings of the present study. Funding: None