Combined EXAFS, XRD, DRIFTS, and DFT Study of Nano Copper Based Catalysts for CO2 Hydrogenation

Highly monodispersed CuO nanoparticles (NPs) were synthesized via continuous hydrothermal flow synthesis (CHFS) and then tested as catalysts for CO2 hydrogenation. The catalytic behavior of unsupported 11 nm sized nanoparticles from the same batch was characterized by diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), extended X-ray absorption fine structure (EXAFS), X-ray diffraction (XRD), and catalytic testing, under CO2/H2 in the temperature range 25–500 °C in consistent experimental conditions. This was done to highlight the relationship among structural evolution, surface products, and reaction yields; the experimental results were compared with modeling predictions based on density functional theory (DFT) simulations of the CuO system. In situ DRIFTS revealed the formation of surface formate species at temperatures as low as 70 °C. DFT calculations of CO2 hydrogenation on the CuO surface suggested that hydrogenation reduced the CuO surface to Cu2O, which facilitated the formation of formate. In situ EXAFS supported a strong correlation between the Cu2O phase fraction and the formate peak intensity, with the maxima corresponding to where Cu2O was the only detectable phase at 170 °C, before the onset of reduction to Cu at 190 °C. The concurrent phase and crystallite size evolution were monitored by in situ XRD, which suggested that the CuO NPs were stable in size before the onset of reduction, with smaller Cu2O crystallites being observed from 130 °C. Further reduction to Cu from 190 °C was followed by a rapid decrease of surface formate and the detection of adsorbed CO from 250 °C; these results are in agreement with heterogeneous catalytic tests where surface CO was observed over the same temperature range. Furthermore, CH4 was detected in correspondence with the decomposition of formate and formation of the Cu phase, with a maximum conversion rate of 2.8% measured at 470 °C (on completely reduced copper), supporting the indication of independent reaction pathways for the conversion of CO2 to CH4 and CO that was suggested by catalytic tests. The resulting Cu NPs had a final crystallite size of ca. 44 nm at 500 °C and retained a significantly active surface

Complex Pediatric Elbow Injury: An Uncommon Case

BACKGROUND: There is paucity of literature describing complex elbow trauma in the pediatric population. We described a case of an uncommon pediatric elbow injury comprised of lateral condyle fracture associated with posterolateral dislocation of elbow. CASE PRESENTATION: A 12-year-old boy sustained a direct elbow trauma and presented with Milch type II lateral condyle fracture associated with posterolateral dislocation of elbow. Elbow dislocation was managed by closed reduction. The elbow stability was assessed under general anaesthesia, followed by open K-wiring for the lateral condylar fracture fixation. The patient had an uneventful recovery with an excellent outcome at 39 months follow-up. CONCLUSION: Complex pediatric elbow injuries are quite unusual to encounter, the management of such fractures can be technically demanding. Concomitant elbow dislocation should be managed by closed reduction followed by open reduction and internal fixation (K-wires or cannulated screws) of the lateral condyle fracture