Atmospheric CO_(2) capture and photofixation to near-unity CO by Ti^(3+)-V_(o)-Ti^(3+) sites confined in TiO_(2) ultrathin layers

To realize efficient atmospheric CO_(2) chemisorption and activation,abundant Ti^(3+) sites and oxygen vacancies in TiO_(2) ultrathin layers were designed.Positron annihilation lifetime spectroscopy and theoretical calculations first unveil each oxygen vacancy is associated with the formation of two Ti^(3+)sites,giving a Ti^(3+)-V_(o)-Ti^(3+) configuration.The Ti^(3+)-V_(o)-Ti^(3+) sites could bond with CO_(2) molecules to form a stable configuration,which converted the endoergic chemisorption step to an exoergic process,verified by in-situ Fourier-transform infrared spectra and theoretical calculations.Also,the adjacent Ti^(3+)sites not only favor CO_(2) activation into COOH*via forming a stable Ti^(3+)–C–O–Ti^(3+) configuration,but also facilitate the rate-limiting COOH^(*)scission to CO^(*)by reducing the energy barrier from 0.75 to 0.45 e V.Thus,the Ti^(3+)-V_(o)-TiO_(2) ultrathinlayers could directly capture and photofix atmospheric CO_(2) into near-unity CO,with the corresponding CO_(2)-to-CO conversion ratio of ca.20.2%.

Insights into the dual-roles of alloying elements in the growth of Sn whiskers

The growth of Sn whiskers from Ti_(2)SnC/Sn-X(X=Sn,Bi,Pb,Ga)samples was studied in this work to understand the effect of alloying elements on whiskering behaviors.The mobility of source Sn atoms relating with the formation and migration of defects was found to be the critical factor dominating the growth rate,with the gathering of which to grow whiskers on the surface acts as an effective means to lower the enthalpy.As a result,the source Sn atoms would migrate to whisker root spontaneously,making the growth of whiskers the nature of materials,and external factors like compressive stress or oxidation are no more necessary but facilitate the whiskering process by promoting the mobility of source Sn atoms.

Characteristics and time resolutions of two CeBr_(3) gamma-ray spectrometers

Purpose The purpose of this work is to study the pulse shape,energy resolution,non-proportionality of energy response for gamma-rays,and time characteristics of CeBr_(3) detector.Method The time and energy responses of two CeBr_(3) detectors were characterized by an analog method and a digital method using a set of standardγ-ray sources.The pulse shape,energy resolution and non-proportionality(nPR)of energy response forγ-rays were characterized using the analog method.For the analog method,the high voltage applied to PMTs,parameters of walk and external delay of constant fraction discriminator were optimized.For the digital method,a CEAN 1729A digitizer with sampling frequency of 2 GS/s and resolution of 11 bit,and a digital constant fraction discrimination technique were used to study the time performance of the two CeBr_(3) detectors.Then,the coincidence time resolutions of the CeBr_(3) detectors for the gamma peaks of ^(22)Na and ^(60)Co were measured using the two methods.Results The t_(rise),lifetimeτ,t_(fall) for CeBr_(3)21^(#)and 22^(#)are 11.2 ns,23.8 ns,50.2 ns,and 10.4 ns,26.5 ns,58.6 ns,respectively.The measured non-proportionality of CeBr_(3)21^(#)and 22^(#)are 1.08%and 2.22%,respectively.The time resolutions of the two CeBr_(3) detectors are 244±2 ps and 248±3 ps at the energy peaks of ^(60)Co source,and 336±2 ps and 335±3 ps at 511 keV for the analog and the digital methods.Conclusions The time resolutions obtained by the analog method and the digital method are almost identical.The CeBr_(3) detector is a good option in the applications such as half-life measurements,ToF-PET and high counting rate conditions.Furthermore,it is a goodγ-ray spectrometer owing to the preferable energy resolution and non-internal activity.

Coordination-driven structure reconstruction in polymer of intrinsic microporosity membranes for efficient propylene/propane separation

Polymers of intrinsic microporosity(PIMs),integrating unique microporous structure and solution-processability,are one class of the most promising membrane materials for energy-efficient gas separations.However,the micropores generated from inefficient chain packing often exhibit wide pore size distribution,making it very challenging to achieve efficient olefin/paraffin separations.Here,we propose a coordination-driven reconstruction(CDR)strategy,where metal ions are incorporated into amidoxime-functionalized PIM-1(AO-PIM)to in situ generate coordination crosslinking networks.By varying the type and content of metal ions,the resulting crosslinking structures can be optimized,and the molecular sieving capability of PIM membranes can be dramatically enhanced.Particularly,the introduction of alkali or alkaline earth metals renders more precise micropores contributing to superior C3H6/C3H8 separation performance.K+incorporated AO-PIM membranes exhibit a high ideal C3H6/C3H8 selectivity of 50,surpassing almost all the reported polymer membranes.Moreover,the coordination crosslinking structure significantly improves the membrane stability under higher pressure as well as the plasticization resistant performance.We envision that this straightforward and generic CDR strategy could potentially unlock the potentials of PIMs for olefin/paraffin separations and many other challenging gas separations.