NMR studies of stock process water and reaction pathways in hydrothermal carbonization of furfural residue

Hydrothermal carbonization(HTC) is a valuable approach to convert furfural residue(FR) into carbon material. The prepared biochars are usually characterized comprehensively, while the stock process water still remains to be studied in detail. Herein, a NMR study of the main components in stock process water generated at different HTC reaction conditions was reported. Various qualitative and quantitative NMR techniques(~1H and ^(13)C NMR,~1H-~1H COSY and ~1H-^(13)C HSQC etc.) especially 1D selective gradient total correlation spectroscopy(TOCSY NMR) were strategically applied in the analysis of HTC stock process water. Without separation and purification, it was demonstrated that the main detectable compounds are 5-hydroxymethylfurfural, formic acid, methanol, acetic acid, levulinic acid, glycerol, hydroxyacetone and acetaldehyde in this complicate mixture. Furthermore, the relationship between the concentration of major products and the reaction conditions(180-240 ℃ at 8 h, and 1-24 h at 240 ℃) was established. Finally, reasonable reaction pathways for hydrothermal conversion of FR were proposed based on this result and our previously obtained characteristics of biochars. The routine and challenging NMR methods utilized here would be an alternative other than HPLC or GC for biomass conversion research and can be extended to more studies.

Non-Monotonic Evolution of Carrier Density and Mobility under Thermal Cycling Treatments in Dirac Semimetal Cd_(3)As_(2) Microbelts

Tunable carrier density plays a key role in the investigation of novel transport properties in three-dimensional topological semimetals.We demonstrate that the carrier density,as well as the mobility,of Dirac semimetal Cd_(3)As_(2) nanoplates can be effectively tuned via in situ thermal treatment at 350 K for one hour,resulting in non-monotonic evolution by virtue of the thermal cycling treatments.The upward shift of Fermi level relative to the Dirac nodes blurs the surface Fermi-arc states,accompanied by an anomalous phase shift in the oscillations of bulk states,due to a change in the topology of the electrons.Meanwhile,the oscillation peaks of bulk longitudinal magnetoresistivity shift at high fields,due to their coupling to the oscillations of the surface Fermi-arc states.Our work provides a thermal control mechanism for the manipulation of quantum states in Dirac semimetal Cd_(3)As_(2) at high temperatures,via their carrier density.

Flexible design of gradient multilayer nanofilms coated on carbon nanofibers by atomic layer deposition for enhanced microwave absorption performance

阻抗匹配为完成高效率的微波吸收器是重要的。象纯金属和碳 nanomaterials 那样的绝缘的损失材料的高传导性通常由于在吸收器和表情之间匹配的低阻抗导致差的吸收。因为他们的吸引人的特征，碳 nanostructures 很包括低密度，高表面区域，和好稳定性为高效率的吸收正在答应候选人。此处，新策略被建议改进作为一个例子用 electrospun 碳 nanofibers 绝缘的损失材料匹配的阻抗。碳 nanofibers 与明确地设计的坡度是涂的有逐渐地增加 electroconductibility 的多层的 nanofilms 由与不同艾尔 2 O 3 内容(偶氮) 旁边原子层免职。也就是，坡度 nanofilms 由绝缘的电影的五层组成纯艾尔 2 O 3, 偶氮(5:1，到艾尔 2 O 3), 纯 ZnO，偶氮(10:1 ) ，并且偶氮(20:1 ) 。万用的坡度电影用作中间的层调节在空气和碳 nanofiber 表面之间匹配的阻抗。因此，与讲道理地选择的厚度的电影显著地展出的坡度涂的碳 nanofibers 提高了微波吸收性能，和最佳的思考损失活动范围在有仅仅 1.8 公里的厚度的 16.2 GHz 的 58.5 dB。这个工作能进一步帮助理解阻抗匹配到微波吸收的贡献。我们的策略是一般的并且能被使用在新窗户中在另外的 fields.Open

Activating interfacial S sites of MoS_(2) boosts hydrogen evolution electrocatalysis

The hydrogen evolution reaction(HER)of molybdenum disulfide(MoS_(2))is limited in alkaline and acid solution because the active sites are on the finite edge with extended basal plane remaining inert.Herein,we activated the interfacial S sites by coupling with Ru nanoparticles on the inert basal plane of MoS_(2)nanosheets.The density functional theory(DFT)calculation and experimental results show that the interfacial S electronic structure was modulated.And the results of∆G H*demonstrate that the adsorption of H on the MoS_(2)was also optimized.With the advantage of interfacial S sites activation,the Ru-MoS_(2)needs only overpotential of 110 and 98 mV to achieve 10 mA·cm^(–2)in both 0.5 M H_(2)SO_(4)and ^(1) M KOH solution,respectively.This strategy paves a new way for activating the basal plane of other transition metal sulfide electrocatalysts for improving the HER performance.

Engineering defects and adjusting electronic structure on S doped MoO2 nanosheets toward highly active hydrogen evolution reaction

The electrocatalytic hydrogen evolution reaction(HER)is one of the most promising ways for low-cost hydrogen production in the future.In this work,hetero S atoms were introduced into the MoO2 to enhance the catalytic activity by simultaneously adjusting electron structure,engineering lattice defect,and increasing oxygen vacancies.And the S doped MoO2 nanosheets with proper S doping amount show the enhanced performance for HER.The optimized catalyst shows a small onset overpotential as low as 120 mV,a low overpotential of 176 mV at the current density of 10 mA/cm^2 which is decreased 166 mV compared to that of the pristine MoO2 nanosheets,a low Tafel slope of 57 mV/decade,and a high turnover frequency of 0.13 H2/s per active site at 150 mV.This finding proposes an effective strategy to prepare nonprecious metal oxide catalyst for enhancing HER performance by rationally doping hetero atoms.