RESUMO
The introduction of high-valence state elements and highly active species is promisingly desired to design superior electrocatalysts for water electrolysis. Exploring scalable synthetic strategies is necessary for an in-depth understanding of the mechanism of improving electrocatalytic performance. But it remains challenging. Herein, several electrocatalysts through element doping are prepared. The obtained Mo-CoP3 -2@FeOOH samples show the overpotentials (OER) of 232 mV (alkaline seawater) and 262 mV (KOH electrolyte). As HER catalyst, it also presents an excellent electrocatalytic performance. The above electrocatalysts are utilized as anode/cathode to assemble devices for alkaline seawater/water electrolysis, which delivers a cell voltage of 1.58 V and durability of 350 h. Density functional theory calculations reveal that Mo ion doping and FeOOH significantly enhance the density states of the Fermi level and tune the position of the d-band center. It expedites the charge transfer and decreases the adsorption energy of intermediates. It demonstrates that transition-metal phosphides coated with highly active FeOOH offer an effective route to fabricate high-performance and durable catalysts for seawater/water electrolysis.
RESUMO
As a paradigm of exploiting electronic-structure engineering on semiconductor superlattices to develop advanced dielectric film materials with high electrical energy storage, the n*AlN/n*ScN superlattices are systematically investigated by first-principles calculations of structural stability, band structure and dielectric polarizability. Electrical energy storage density is evaluated by dielectric permittivity under a high electric field approaching the uppermost critical value determined by a superlattice band gap, which hinges on the constituent layer thickness and crystallographic orientation of superlattices. It is demonstrated that the constituent layer thickness as indicated by larger n and superlattice orientations as in (111) crystallographic plane can be effectively exploited to modify dielectric permittivity and band gap, respectively, and thus promote energy density of electric capacitors. Simultaneously increasing the thicknesses of individual constituent layers maintains adequate band gaps while slightly reducing dielectric polarizability from electronic localization of valence band-edge in ScN constituent layers. The AlN/ScN superlattices oriented in the wurtzite (111) plane acquire higher dielectric energy density due to the significant improvement in electronic band gaps. The present study renders a framework for modifying the band gap and dielectric properties to acquire high energy storage in semiconductor superlattices.
RESUMO
The psbA-trnH regions of Dendrobium species of Fengdous were sequenced by our research group. The psbA-trnH sequences of fifteen Dendrobium species were analyzed with software MEGA 4.0. The results showed that the lengths of sequences varied from 721 to 767 bp. The variable sites were 42 while the informative sites were 11. Genetic distances were calculated using the Kimura 2-parameter model. Genetic distances varied from 0.0013-0.0183 among fifteen species while the average genetic distance was 0.0148. The interspecies differences of psbA-trnH regions were demonstrated. Six indels happened in this fragment, which led to the great difference of sequence lengths among fifteen species. We found that there were no population differences in the psbA-trnH region of various species of Fengdous so far. By using the database of various Dendrobium species of Fengdous and two genetics software, the botanical origin of the inspected species of Fengdous was authenticated successfully by sequencing the psbA-trnH regions. The psbA-trnH region of cpDNA can be used as a candidate marker for authentication of Dendrobium species of Fengdous.
