Structural and Reactivity Effects of Secondary Metal Doping into Iron-Nitrogen-Carbon Catalysts for Oxygen Electroreduction.

While improved activity was recently reported for bimetallic iron-metal-nitrogen-carbon (FeMNC) catalysts for the oxygen reduction reaction (ORR) in acid medium, the nature of active sites and interactions between the two metals are poorly understood. Here, FeSnNC and FeCoNC catalysts were structurally and catalytically compared to their parent FeNC and SnNC catalysts. While CO cryo-chemisorption revealed a twice lower site density of M-Nx sites for FeSnNC and FeCoNC relative to FeNC and SnNC, the mass activity of both bimetallic catalysts is 50-100% higher than that of FeNC due to a larger turnover frequency in the bimetallic catalysts. Electron microscopy and X-ray absorption spectroscopy identified the coexistence of Fe-Nx and Sn-Nx or Co-Nx sites, while no evidence was found for binuclear Fe-M-Nx sites. 57Fe Mössbauer spectroscopy revealed that the bimetallic catalysts feature a higher D1/D2 ratio of the spectral signatures assigned to two distinct Fe-Nx sites, relative to the FeNC parent catalyst. Thus, the addition of the secondary metal favored the formation of D1 sites, associated with the higher turnover frequency.

P-block single-metal-site tin/nitrogen-doped carbon fuel cell cathode catalyst for oxygen reduction reaction.

This contribution reports the discovery and analysis of a p-block Sn-based catalyst for the electroreduction of molecular oxygen in acidic conditions at fuel cell cathodes; the catalyst is free of platinum-group metals and contains single-metal-atom actives sites coordinated by nitrogen. The prepared SnNC catalysts meet and exceed state-of-the-art FeNC catalysts in terms of intrinsic catalytic turn-over frequency and hydrogen-air fuel cell power density. The SnNC-NH3 catalysts displayed a 40-50% higher current density than FeNC-NH3 at cell voltages below 0.7 V. Additional benefits include a highly favourable selectivity for the four-electron reduction pathway and a Fenton-inactive character of Sn. A range of analytical techniques combined with density functional theory calculations indicate that stannic Sn(IV)Nx single-metal sites with moderate oxygen chemisorption properties and low pyridinic N coordination numbers act as catalytically active moieties. The superior proton-exchange membrane fuel cell performance of SnNC cathode catalysts under realistic, hydrogen-air fuel cell conditions, particularly after NH3 activation treatment, makes them a promising alternative to today's state-of-the-art Fe-based catalysts.

Synthesis, characterization, and photoluminescence of Er2O3-Er2SO2 nanoparticles on reduced graphene oxide.

Thermal reduction of erbium nitrate and S-doped reduced graphene oxide (rGO) mixture resulted in the formation of small (∼3-18 nm sized) Er2O3-Er2SO2 nanoparticles with a high degree of surface coverage on the reduced GO support. The morphology, structure, and the chemical composition of the synthesized nanoparticles have been studied by scanning and transmission electron microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and by optical spectroscopies. The rGO-supported Er2O3-Er2SO2 nanoparticles (Er2O3-Er2SO2/rGO) demonstrate sufficiently strong light emission (luminescence and upconversion) in the visible and near-infrared range via intra-4f Er3+ optical transitions. The reported synthetic approach demonstrates a novel method for synthesizing Er-containing nanoparticles for sensor applications.

Anode catalysts for direct hydrazine fuel cells: from laboratory test to an electric vehicle.

Novel highly active electrocatalysts for hydrazine hydrate fuel cell application were developed, synthesized and integrated into an operation vehicle prototype. The materials show in both rotating disc electrode (RDE) and membrane electrode assembly (MEA) tests the world highest activity with peak current density of 16,000 A g(-1) (RDE) and 450 mW cm(-2) operated in air (MEA).

A challenging case of spontaneous idiopathic omental infarction in a trisomy 21 patient.

Background: Omental infarction (OI) is a rare cause of acute abdominal pain that is often missed out. Due to its non-specific presentation can mimic other commoner conditions such as acute appendicitis, acute diverticulitis, and tuberculosis abdomen. Case presentation: We present a 42-year-old gentleman with trisomy 21 presenting right iliac fossa pain. Examination revealed tenderness in the right lower quadrant and blood parameters showed leucocytosis. With an initial impression of acute appendicitis, the patient was subjected to surgery. Intraoperatively, there were abnormalities to the omentum suggestive of OI, resulting in partial omentectomy. Symptom resolution occurred immediately and the patient was discharged early. Conclusion: OI is a rare cause of acute abdomen that can mimic other abdominal pathologies. In trisomy 21 patients who present with acute abdomen, thorough assessments including preoperative imaging are advisable. Diagnostic laparoscopy is recommended as OI can be managed via minimally invasive surgery, hence ensuring good surgical outcomes.