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In this work, the single Rh atom anchored by N vacancy of C3N monolayer for CO oxidations has been studied by using first-principles calculations. The stability for a single Rh atom in N vacancy of C3N monolayer is detailed investigated. The sizeable binding energy and diffusion barrier of the Rh atom in the N vacancy and the ab initial molecule dynamic simulations at 400 K all verify that the Rh is stable at the N vacancy of the C3N monolayer. We also have examined the bi-molecule Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) and the tri-molecule LH mechanisms on the Rh @ C3N. It is found that the barriers for the rate-limiting step for bi-molecule ER and LH are so significant (1.35, 1.15 eV), while for the tri-molecule LH mechanism, the barrier of the rate-limiting step is only 0.49 eV, which means the tri-molecule LH mechanism is more likely to occur at room temperature on the Rh @ C3N. Thus, our results will shed light on the future design for low-temperature CO oxidation using single-atom catalysts. [ABSTRACT FROM AUTHOR]

Surface-deposited sediment in urban area is an essential environmental medium for assessing heavy metal contamination. A total of 10 sampling trips were conducted to collect road-deposited and roof-deposited sediments for the comparison of nickel (Ni), copper (Cu), cadmium (Cd), lead (Pb), zinc (Zn), and chromium (Cr) contamination characteristics. Results indicated that roof sediment appeared to have a finer size distribution than road sediments. Roof sediment indicated higher metal concentration and lower surface loading than road sediment. The impact of particle size on heavy metal contamination was quantified by using the developed pioneering term of finer particle effect factor; it differed according to surface types and grain size fraction. Particles in individual grain size fraction showed different contribution to the surface loading for bulk sediments. No consistent trend was found for the grain size fraction loading along with grain size for the studied heavy metals for road sediments. In contrast, an asymmetric 'W' trend was observed for the roof sediments, and it had the following results: Fraction of <63 and 250-500 μm showed higher loading, while fraction of 90-125 and >850 μm indicated the smaller loading. Findings above facilitated the appropriate management practice selection for the treatment of surface-deposited sediments. [ABSTRACT FROM AUTHOR]

The dissociation barriers of O and the adsorption energies of atomic O on the icosahedron M@Pd12, double icosahedron M2@Pd17 core-shell nanoclusters, and the M@Pd (M = Mn, Fe, Co, Ni, Cu, Pd) nanowires (NWs) are studied. It is found that the M@Pd NWs can probably serve as good catalysts for oxygen reduction reaction with both small O dissociation energy (0.10-0.23 eV) and O adsorption energy (1.19-1.28 eV). The reasons for the advantage of the M@Pd NWs are discussed in detail. [ABSTRACT FROM AUTHOR]