用于电催化硝酸盐还原的铜基催化剂

近年来,电催化硝酸盐还原(ENitRR)在常温常压合成氨中受到广泛关注,与传统的Haber-Bosch合成氨工艺相比,ENit RR的能耗更低,反应条件更温和。ENitRR电催化剂的合理设计和优化对于硝酸盐脱氧和加氢至关重要。铜基催化材料凭借其特殊结构、低成本和优异的催化性能,通过各种形态和电子结构的调节策略,近年来成为极具前景的电催化剂。为了进一步探索这一领域的新可能性,本文以铜基电催化剂的合理调控为典型实例,总结了有效提高ENit RR产氨率和转化效率的设计策略。在介绍ENit RR反应机理的基础上,总结了改变Cu基电催化剂的结构和性能的6种策略,即形貌调制、合金工程、晶面调控、单原子结构、铜化合物和其他材料复合的构建,并讨论了催化剂调制与相应ENit RR性能之间的关系。最后,提出了基于铜基电催化剂的ENitRR面临的挑战和未来应该关注的研究方向,以期为从事水体硝酸盐电化学处理的研究人员提供一定的参考和启发。

TiO_(2) nanorods based self-supported electrode of 1T/2H MoS_(2) nanosheets decorated by Ag nano-particles for efficient hydrogen evolution reaction

Molybdenum disulfide(MoS_(2))has shown significant promise as an economic hydrogen evolution reaction(HER)catalyst for hydrogen generation,but its catalytic performance is still lower than noble metalbased catalysists.Herein,a silver nanoparticles(Ag NPs)-decorated 1T/2H phase layered MoS_(2) electrocatalyst grown on titanium dioxide nanorod arrays(Ag NPs/1T(2H)MoS_(2)/TNRs)was prepared through acid-tunable ammonium ion intercalation.Taking advantage of MoS_(2) layered structure and crystal phase controllability,as-prepared Ag NPs/1T(2H)MoS_(2)/TNRs exhibited ultrahigh HER activity.As-proposed strategy combines facile hydrogen desorption(Ag NPs)with efficient hydrogen adsorption(1T/2H MoS_(2))effectively circumventes the kinetic limitation of hydrogen desorption by 1T/2H MoS_(2).The as-prepared Ag NPs/1T(2H)MoS_(2)/TNRs electrocatalyst exhibited excellent HER activity in 0.5 mol/L H2SO4 with low overpotential(118 mV vs.reversible hydrogen electrode(RHE))and small Tafel slope(38.61 mV/dec).The overpotential exhibts no obvious attenuation after 10 h of constant current flow.First-principles calculation demonstrates that as-prepared 1T/2H MoS_(2) exhibit a large capacity to store protons.These protons can be subsequently transferred to Ag NPs,which significantly increases the hydrogen coverage on the surface of Ag NPs in HER process and thus change the rate-determining step of HER on Ag NPs from water dissociation to hydrogen recombination.This study provides a unique strategy to improve the catalytic activity and stability for MoS_(2)-based electrocatalyst.

Dynamical model of encapsulated gas microbubble under ultrasound based on elastic mechanics

Based on the theory of elastic mechanics, a dynamical model of an encapsulated gas microbubble under ultrasound is presented.The dynamical motion of the microbubble is divided into three states: buckled, elastic, and ruptured. The model describes the compression-only behavior appropriately and derives the transient variation of the resonance frequency of the damped oscillation and the relation between the critical rupture radius and initial outer radius. The normal stress in the tangential direction plays the principal role in the rupture and buckling of the encapsulating shell, resulting in likely rupture for a larger microbubble and resistance to rupture for a thicker-shell microbubble. Comparison of proposed dynamical model with Marmottant's model has been given. The dynamical model can be employed in ultrasound medical diagnostics and therapy of drug incorporation or extravasation through further understanding the influence of the encapsulating shell.

Dual-functional sites for synergistic adsorption of Cr(Ⅵ)and Sb(Ⅴ)by polyaniline-TiO_(2) hydrate:Adsorption behaviors,sites and mechanisms

Removal of chromium(Cr)and antimony(Sb)from aquatic environments is crucial due to their bioaccumulation,high mobility and strong toxicity.In this work,a composite adsorbent consisting of Ti(OH)n(4–n)+and polyaniline(PANI)was designed and successfully synthesized by a simple and eco-friendly method for the uptake of Cr(VI)and Sb(V).The synthetic PANI/TiO_(2)composites exhibited excellent adsorption capacities for Cr(VI)and Sb(V)(394.43 mg/g for Cr(VI)and 48.54 mg/g for Sb(V)),wide pH applicability and remarkable reusability.The adsorption of Cr(VI)oxyanions mainly involved electrostatic attraction,hydrogen bonding and anion-πinteractions.Based on X-ray photoelectron spectroscopy and FT-IR analysis,the adsorption sites were shown to be hydroxyl groups,amino/imino groups and benzene rings.Sb(V)was adsorbed mainly through hydrogen bonds and surface complexation to form Ti-O-Sb complexes.The formation of Cr-O-Sb in the dual system demonstrated the synergistic adsorption of Cr(VI)and Sb(V).More importantly,because of the different adsorption sites,the adsorption of Cr(VI)and Sb(V)occurred independently and was enhanced to some extent in the dual system.The results suggested that PANI/TiO_(2)is a promising prospect for practical wastewater treatment in the removal of Cr(VI)and Sb(V)from wastewater owing to its availability,wide applicability and great reusability.

Insight into the effect of surface carboxyl and amino groups on the adsorption of titanium dioxide for acid red G

In this study,TiO_(2)functionalized with organic groups were prepared to study the effect of carboxyl and amino groups on the adsorption behavior of TiO_(2)for the removal of acid red G(ARG)as an anionic dye from aqueous solution.TiO_(2)was successfully modified with carboxyl and amino groups by using the hydrolysis method with oxalic acid(OAD,with two carboxyl groups),ethylenediamine(EDA,with two amino groups)and DL-alanine(DLA,with one carboxyl group and one amino group)at low temperature(65℃)and labeled as OAD-TiO_(2),EDA-TiO_(2)and DLA-TiO_(2),respectively.The ARG uptake by the functionalized TiO_(2)samples was largely dependent on the functional groups.The interaction between ARG and the functional organic groups on the TiO_(2)samples plays an important role in the adsorption process,which leads to the excellent adsorption performance(higher capacity and faster adsorption rate)of the functionalized TiO_(2)samples than that of P25(commercial TiO_(2)without modification).Furthermore,there is no obvious loss of the adsorption capacity for the functionalized TiO_(2)even after 5 adsorption-desorption cycles,which indicated the good reusability of the modified TiO_(2)samples for anionic dye removal from aqueous solution.