As a clean and sustainable energy source, hydrogen is widely considered as an engine fuel by top researchers. In view of the fact that the uneven fuel mixture of diesel fuel deteriorated the combustion and emissions process, it is expected to adopt diesel and hydrogen dual-fuel combustion technology to optimize combustion and heat release of diesel engine. In this study, experiments are carried out on a diesel engine and the combustion characteristics of the engine with different hydrogen ratios (RH) are compared. It has been found that hydrogen addition is conducive to accelerate the heat release rate and improve the thermal efficiency. Specifically, compared with pure diesel conditions, the peak pressure increased by 7.7% and the cumulative heat release rate increased by 3.7% under the condition of RH of 20%. Moreover, although the effect on the ignition delay period is not clear, the higher RH brings about earlier heat release center and more cumulative heat release while enhancing the heat release of premixed combustion reducing the diffusion combustion and post-combustion.
(+)‐Tartaric acid‐catalyzed aminobromination of α,β‐unsaturated ketones, α,β‐unsaturated esters and simple olefins utilizing TsNH2/NBS as the nitrogen/halogen sources at room temperature without protection of inert gases achieved good yields (up to 92% yield) of vicinal haloamino products with excellent regio‐ and stereoselectivity, even just 10% of (+)‐tartaric acid was used as catalyst. The regio‐ and stereochemistry was unambiguously confirmed by X‐ray structural analysis of products 2b and 12c . The electron‐rich and deficient olefins show significant differences in activity to the aminobromination reaction and give the opposite regioselectivities. The 21 cases have been investigated which indicated that our protocol has the advantage of a large scope of olefins. Additionally, tartaric acid as catalyst has the advantage of avoiding any hazardous metals retained in products. 相似文献
Directly splitting water into H2 and O2 with solar light is extremely important; however, the overall efficiency of water splitting still remains extremely low. Two types of ultrathin semiconductor layers with the same elements and the same thicknesses were designed to uncover how different atomic arrangements influence water‐splitting efficiency thermodynamically and kinetically. As an example, tetrahedrally coordinated blende and octahedrally coordinated rocksalt CoO atomic layers with nearly the same thicknesses were synthesized for the first time. The blende CoO atomic layers have a smaller Eg and abundant d–d internal transition features relative to the rocksalt CoO atomic layers, which ensure enhanced visible‐light harvesting ability. Density functional theory calculations reveal that the Bader charge for Co atoms in blende CoO atomic layers is larger than that of the rocksalt CoO atomic layers, which facilitates photocarrier transfer kinetics, as verified by photoluminescence spectra and time‐resolved fluorescence emission decay spectra. In situ FTIR spectra and energy calculations reveal that the *OOH dissociation step is the rate‐limiting step, where the blende CoO atomic layers possess a smaller *OOH dissociation energy thanks to their higher Bader charge and stronger steric effect, as confirmed by the elongated Co?OOH bonds. The blende CoO atomic layers exhibit visible‐light‐driven H2 and O2 formation rates of 4.43 and 2.63 μmol g?1 h?1, roughly 3.7 times higher than those of the rocksalt CoO atomic layers. 相似文献
On-surface synthesis of high-quality nanoporous graphene (NPG) for application in nanotechnology and nanodevices remains challenging. Rational design of molecular precursors and proper kinetic control over the reaction process are the two key factors to tune the synthesis. Herein, we report a detailed study of the coupling reactions of a planar halogen-substituted nanographene molecular precursor, hexaiodo-peri-hexabenzocoronene (I6-HBC), on the Au(111) surface in the synthesis of NPG. The influence of three basic kinetic processes – molecular adsorption, migration, and coupling – on the synthesis was investigated. The results show that the HBC molecules deposited at low temperature predominantly desorb from the Au(111) surface during the annealing process, whereas depositing the precursor molecules onto a hot surface (700 K) can lead to the formation of NPG. However, at such a high surface temperature, simultaneous intermolecular dehydrogenative coupling between HBC monomers can hinder the ordered growth of NPG through Ullmann coupling. Moreover, the deposition rate of the precursors greatly influences the growth morphology of the NPG nanostructures. 相似文献