Urea oxidation, a key process in energy and environmental science, faces challenges because of the insu cient understanding of its mechanism and the lack of e cient catalysts. Here we demonstrate that nickel ferrocyanide (Ni 2 Fe(CN) 6 ) molecular catalyst supported on Ni form can drive urea oxidation reaction (UOR) with the record electrochemical activity and stability among all supported catalysts reported so far. A combination of kinetics data, in-situ spectroscopic measurements and energy computations suggests a new UOR pathway that delivers such outstanding performance. Different from most studied Ni-based catalysts with NiOOH derivative as a real catalytically active site for UOR, Ni 2 Fe(CN) 6 appears to be a next-generation catalyst able to directly facilitate a two-step reaction pathway involving a critical reaction of intermediate ammonia's production (on Ni site) and oxidation (on Fe site).Due to the alternative rate-determining step with a more favorable thermal energetics, Ni 2 Fe(CN) 6 broke the limiting activity of the reported so far UOR catalysts. As a result, the UOR process on Ni 2 Fe(CN) 6 can replace conventional water oxidation process in various energy-saving systems for hydrogen and hydrogen peroxide production.
Supplemental Table 1. Detailed results from the mixed-effected models with interaction terms between the treatment effect and time Outcomes Variables Coefficient (95%CI) P Value 6MWD (m) Intervention 52.7 (22.9 to 82.6) 0.001
The
construction of stable active site in nanocatalysts is of great
importance but is a challenge in heterogeneous catalysis. Unexpectedly,
coordination-unsaturated and atomically dispersed copper species were
constructed and stabilized in a sintered copper–ceria catalyst
through air-calcination at 800 °C. This sintered copper–ceria
catalyst showed a very high activity for CO oxidation with a CO consumption
rate of 6100 μmolCO·gCu
–1·s–1 at 120 °C, which was at least 20
times that of other reported copper catalysts. Additionally, the excellent
long-term stability was unbroken under the harsh cycled reaction conditions.
Based on a comprehensive structural characterization and mechanistic
study, the copper atoms with unsaturated coordination in the form
of Cu1O3 were identified to be the sole active
site, at which both CO and O2 molecules were activated,
thus inducing remarkable CO oxidation activity with a very low copper
loading (1 wt %).
The most direct route to the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in combustion and thermal processes is the gas-phase reaction of chemical precursors such as chlorinated phenols. Detailed insight into the mechanism and kinetics properties is a prerequisite for understanding the formation of PCDD/Fs. In this paper, we carried out molecular orbital theory calculations for the homogeneous gas-phase formation of PCDD/Fs from 2-chlorophenol (2-CP). The profiles of the potential energy surface were constructed, and the possible formation pathways are discussed. The single-point energy calculation was carried out at the MPWB1K/ 6-311+G(3f,2p) level. Several energetically favorable formation pathways were revealed for the first time. The rate constants of crucial elementary steps were deduced over a wide temperature range of 600 approximately 1200 K using canonical variational transition-state theory (CVT) with small curvature tunneling contribution (SCT). The rate-temperature formulas were fitted. The ratio of PCDD to PCDF formed shows strong dependency on the reaction temperature and chlorophenoxy radicals (CPRs) concentration.
nanostructures of trigonal selenium (t-Se) were synthesized by the reduction of H 2 SeO 3 in different solvents with a sonochemical method. The 1D structure of t-Se was formed by the anisotropic growth of selenium crystalline, and the morphology of the products highly depends on the reaction conditions including ultrasonic mode (e.g., frequency, power, and time), aging time, and solvent. Single crystalline trigonal selenium nanotubes with diameters of less than 200 nm and nanowires with diameters of 20-50 nm have been synthesized. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy-dispersive spectrometry (EDS), and Raman spectra were used to characterize the products. The formation process of t-Se nanotubes and nanowires were investigated. A sonication-induced directional growth mechanism was proposed for the formation of nanotubes. The further aging of tubes in solution leads to the collapse of the tubular structure and the formation of nanowires.
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