Efficient Ammonia Electrosynthesis from Nitrate on Strained Ruthenium Nanoclusters.

The limitations of the Haber-Bosch reaction, particularly high-temperature operation, have ignited new interests in low-temperature ammonia-synthesis scenarios. Ambient N2 electroreduction is a compelling alternative but is impeded by a low ammonia production rate (mostly <10 mmol gcat-1 h-1), a small partial current density (<1 mA cm-2), and a high-selectivity hydrogen-evolving side reaction. Herein, we report that room-temperature nitrate electroreduction catalyzed by strained ruthenium nanoclusters generates ammonia at a higher rate (5.56 mol gcat-1 h-1) than the Haber-Bosch process. The primary contributor to such performance is hydrogen radicals, which are generated by suppressing hydrogen-hydrogen dimerization during water splitting enabled by the tensile lattice strains. The radicals expedite nitrate-to-ammonia conversion by hydrogenating intermediates of the rate-limiting steps at lower kinetic barriers. The strained nanostructures can maintain nearly 100% ammonia-evolving selectivity at >120 mA cm-2 current densities for 100 h due to the robust subsurface Ru-O coordination. These findings highlight the potential of nitrate electroreduction in real-world, low-temperature ammonia synthesis.

Is propofol a friend or a foe of the pediatric intensivist? Description of propofol use in a PICU*.

OBJECTIVE: The primary objective is to describe the practice patterns of nonprocedural propofol use in a single-center referral PICU. The secondary objective is to describe the rate of concordance of propofol use with the PICU local practice of a maximum mean rate of 4 mg/kg/hr and a maximum duration of 24 hours and to assess for signs and symptoms of propofol infusion syndrome. DESIGN: Retrospective descriptive cohort study. SETTING: PICU of a tertiary care teaching hospital and referral hospital for the Western Canada. PATIENTS: Children 1 month to 17 years old who received a nonprocedural propofol infusion between January 1, 2009, and December 31, 2009. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Two hundred twenty-three infusions (representing 210 unique patients) were included in the study. The median average infusion rate (interquartile range) including boluses was 2.7 mg/kg/hr (1.9-3.6 mg/kg/hr), and the mean infusion duration (SD) was 10.3 hours (6.7 hr). Eighty-seven percent and 98% of infusions were concordant with PICU intensivists self-reported practice maximum rate and duration, respectively. No cases of propofol-related infusion syndrome or deaths associated with propofol infusions were identified. CONCLUSIONS: The use of propofol infusions was in concordance with PICU local practice, and propofol infusion syndrome did not developed in patients. In agreement with previous recommendations, propofol infusions in the PICU appear to be safe when limiting doses to 4 mg/kg/hr and for less than 24 hours; however, appropriate monitoring of adverse effects is still warranted due to absence of robust evidence.