Efficient solar fuel production enabled by an iodide oxidation reaction on atomic layer deposited MoS_(2)

Oxygen evolution reaction(OER)as a half-anodic reaction of water splitting hinders the overall reaction efficiency owing to its thermodynamic and kinetic limitations.Iodide oxidation reaction(IOR)with low thermodynamic barrier and rapid reaction kinetics is a promising alternative to the OER.Herein,we present a molybdenum disulfide(MoS_(2))electrocatalyst for a high-efficiency and remarkably durable anode enabling IOR.MoS_(2)nanosheets deposited on a porous carbon paper via atomic layer deposition show an IOR current density of 10 mA cm^(–2)at an anodic potential of 0.63 V with respect to the reversible hydrogen electrode owing to the porous substrate as well as the intrinsic iodide oxidation capability of MoS_(2)as confirmed by theoretical calculations.The lower positive potential applied to the MoS_(2)-based heterostructure during IOR electrocatalysis prevents deterioration of the active sites on MoS_(2),resulting in exceptional durability of 200 h.Subsequently,we fabricate a two-electrode system comprising a MoS_(2)anode for IOR combined with a commercial Pt@C catalyst cathode for hydrogen evolution reaction.Moreover,the photovoltaic–electrochemical hydrogen production device comprising this electrolyzer and a single perovskite photovoltaic cell shows a record-high current density of 21 mA cm^(–2)at 1 sun under unbiased conditions.

Interfacial Electronic Modulation of Dual-Monodispersed Pt–Ni_(3)S_(2) as Efficacious Bi-Functional Electrocatalysts for Concurrent H_(2) Evolution and Methanol Selective Oxidation

Constructing the efficacious and applicable bifunctional electrocatalysts and establishing out the mechanisms of organic electro-oxidation by replacing anodic oxygen evolution reaction(OER) are critical to the development of electrochemicallydriven technologies for efficient hydrogen production and avoid CO_(2) emission. Herein, the hetero-nanocrystals between monodispersed Pt(~ 2 nm) and Ni_(3)S_(2)(~ 9.6 nm) are constructed as active electrocatalysts through interfacial electronic modulation, which exhibit superior bi-functional activities for methanol selective oxidation and H_(2) generation. The experimental and theoretical studies reveal that the asymmetrical charge distribution at Pt–Ni_(3)S_(2) could be modulated by the electronic interaction at the interface of dual-monodispersed heterojunctions, which thus promote the adsorption/desorption of the chemical intermediates at the interface. As a result, the selective conversion from CH_(3)OH to formate is accomplished at very low potentials(1.45 V) to attain 100 m A cm^(-2) with high electronic utilization rate(~ 98%) and without CO_(2) emission. Meanwhile, the Pt–Ni_(3)S_(2) can simultaneously exhibit a broad potential window with outstanding stability and large current densities for hydrogen evolution reaction(HER) at the cathode. Further, the excellent bi-functional performance is also indicated in the coupled methanol oxidation reaction(MOR)//HER reactor by only requiring a cell voltage of 1.60 V to achieve a current density of 50 m A cm^(-2) with good reusability.

Study on the Mechanisms for Baeyer-Villiger Oxidation of Cyclohexanone with Hydrogen Peroxide in Different Systems

The green and effective Baeyer-Villiger oxidation reaction of cyclohexanone for preparing ε-caprolactone is of particular importance in the synthesis of new polymer materials. We have discussed here several mechanism types of Baeyer-Villiger oxidation of cyclohexanone with H2O2 in different reaction systems. Five main types have been addressed, i. e.: (1) the non-catalyzed reaction type, where the C=O of ketones is activated by H+, which is electrolytically dissociated from H2O2 and H2O, to improve the capability of C=O group for accepting the electron pairs; (2) the thermally activated radical reaction type, where the Criegee intermediate is produced via two steps of radical reaction with ·OH attack, with much more hydroxyl radicals being excited in the presence of TS-1 zeolite; (3) the Brnsted acid catalysis reaction type, where both O-O moiety and C=O group could be activated by Brnsted acid; (4) the solid Lewis acid catalyzed C=O of the substrate activation reaction type through enhancing the donor-acceptor interaction between the antibonding π*C=O orbital of cyclohexanone and HOMO of Sn-containing zeolites; and (5) the solid Lewis acid catalyzed H2O2 to form Me-OOH oxidative species by converting the highest occupied molecular orbital (HOMO) of Ti-OOH into a singly occupied molecular orbital (SOMO), making the O-O group highly electrophilic to attack the C=O of cyclohexanone during the Baeyer-Villiger oxidation process. In the end, we have also compared the different mechanisms and put forward our opinions on the development direction of catalytic materials aiming at eco-friendly Baeyer-Villiger oxidation of cyclohexanone in the years to come.

Progress and prospect of Pt-based catalysts for electrocatalytic hydrogen oxidation reactions

To achieve the goals of the peak carbon dioxide emissions and carbon neutral,the development and utilization of sustainable clean energy are extremely important.Hydrogen fuel cells are an important system for converting hydrogen energy into electrical energy.However,the slow hydrogen oxidation reaction(HOR)kinetics under alkaline conditions has limited its development.Therefore,elucidating the catalytic mechanism of HOR in acidic and alkaline media is of great significance for the construction of highly active and stable catalysts.In terms of practicality,Pt is still the primary choice for commercialization of fuel cells.On the above basis,we first introduced the hydrogen binding energy theory and bifunctional theory used to describe the HOR activity,as well as the pH dependence.After that,the rational design strategies of Pt-based HOR catalysts were systematically classified and summarized from the perspective of activity descriptors.In addition,we further emphasized the importance of theoretical simulations and in situ characterization in revealing the HOR mechanism,which is crucial for the rational design of catalysts.Moreover,the practical application of Pt-based HOR catalysts in fuel cells was also presented.In closing,the current challenges and future development directions of HOR catalysts were discussed.This review will provide a deep understanding for exploring the mechanism of highly efficient HOR catalysts and the development of fuel cells.

A quantum chemistry study on reaction mechanisms of SO_2 with O_3 and H_2O_2

反应机制那么有 O 3 和 H 22> O 2 用量化学 ab initio 方法被调查。所有反应物，产品，和转变状态的结构在 B3LYP/6-311G+(3df,2p ) 水平被优化，并且精力计算在 G2M 水平被做。那么有 O 3 和 H 22 反应 > O 2 由 O 抽象和哦抽象发生了由那么2,分别地，最后那么形成3+O2( 3Σ g −)和 H 2那么4。为那么 2+O3 反应障碍高度被预言是有 3.61 × 1 的一个率常数的 9.68 kcal/mol 在 300 K 的 0 −23 厘米 3/(molecule · s) ，它在试验性的上面的限制下面。率常数为这预言反应与那在 250 ∼500 K 为标准和技术(NIST ) 由国家研究所提供了一致很好。为那么 2+H2 O 2 反应障碍高度被预言是有 2.48 × 1 的一个率常数的 62.39 kcal/mol 在 300 K 的 0 −61 厘米 3/(molecule · s) 。

电催化两电子水氧化制备过氧化氢的研究进展

过氧化氢(H_(2)O_(2))是一种环境友好的化学氧化剂,广泛应用于水处理、医疗消毒、化学合成等工业领域。电催化两电子水氧化反应(2e^(-)WOR)是一种可以在温和条件下直接从水中生产H_(2)O_(2)的方法。然而,受限于反应机理认识和催化材料设计的不足,2e^(-)WOR的催化选择性和活性仍然较低。本文综述了近年来通过2e^(-)WOR反应路径电合成H_(2)O_(2)的研究进展,首先介绍了2e^(-)WOR的催化机理和研究方法,强调了理论计算加速高选择性、高活性和高稳定性催化剂研究的作用,并讨论了电合成H_(2)O_(2)的不同定量方法和原位表征手段;然后详细总结了高性能2e^(-)WOR电催化剂的调控策略,包括缺陷、掺杂、晶面和界面工程,同时指出了反应器创新设计的重要性;最后展望了电合成H_(2)O_(2)的研究挑战和机遇。

CuMn_(2)O_(4)催化剂臭氧催化甲苯:反应条件和机理分析

为减少目前工业生产排放大量的挥发性有机污染物(VOCs)对环境的影响,采用共沉淀法制备CuMn_(2)O_(4)尖晶石催化剂,将CuMn_(2)O_(4)催化剂结合臭氧(O_(3))催化氧化VOCs具有良好的效果,考察了反应条件对甲苯处理效果的影响,分析CuMn_(2)O_(4)臭氧催化氧化甲苯的反应机理。结果表明,CuMn_(2)O_(4)在臭氧的体积分数为2.1×10^(-3)、反应温度为100℃以及干空气条件下对甲苯的去除率达73%。通过催化表征和原位反应过程分析,证实适当温度和高体积分数的O_(3)可促进活性氧物种(ROS)产生,O_(3)在Mn-O或Cu-O_(v)-Mn分解并生成ROS,而Cu_(0)与Cu^(+)质量分数比w(Cu~0)/w(Cu^(+))可作为甲苯吸附锚点,在反应初期吸附甲苯并促使甲苯在活性位点(Cu-O_(v)-Mn)氧化成苯甲酸,甚至CO_(2)、H_(2)O等小分子物质。

Density Functional Theory Studies on the Mechanism of Activation Formic Acid Catalyzed by Transition Metal Oxide MoO

This paper systematically studies the reaction mechanisms of formic acid catalyzed by transition metal oxide MoO. Three different reaction pathways of Routes I, Ⅱ and Ⅲ were found through studying the reaction mechanism of transition metal oxide MoO catalyzing the formic acid. The transition metal oxide MoO interacts with the C=O double bond to form chiral chain compounds（Routes I and Ⅱ） and metallic compound MoOH2（Route Ⅲ）. In this paper, we have studied the mechanisms of two addition reaction pathways and hydrogen abstraction reaction pathway. Routes I and Ⅱ are both addition reactions, and their products are two different chiral compounds MoO3CH2, which are enantiomeric to each other. In Route Ⅲ, metal compounds MoOH2 and CO2 are obtained from the hydrogen abstraction reaction. Among them, the hydrogen abstraction reaction occurring in Route Ⅲ is more likely to occur than the others. By comparing the results of previous studies on the reaction of MxOy-＋ ROH（M= Mo,W; R = Me, Et）, we found that the hydrogen abstraction mechanism is completely different from the mechanism of oxygen-containing organic compound catalyzed by MxOy.

Efficiency and mechanism of degradation of alachlor in water by O_3/H_2O_2 catalyst system

Alachlor is used widely as a herbicide,but is an environmental endocrine disruptor. O 3/H 2O 2 system is used as catalyst to delve on the degradation efficiency of alachlor. The amount of the catalyst H 2O 2,the pH value of the soluble, the temperature and quality of water sample are changed to investigate the effect of these factors on the degradation of alachlor. The degradation of alachlor is qualitatively analyzed through their GS MS spectra and the possible mechanism of the degradation of alachlor is discussed as well.

Theoretical study of propene oxidation on Bi_2O_3 surfaces

The role of bismuth in the selective oxidation of propene has long been debated. We performed density functional calculations to study the dehydrogenation reaction of propene on Bi2O3 surfaces. Our calculated thermodynamic data reveal that the first dehydrogenation of propene on the most stable(010) surface and the(100) surface are difficult. Our calculations indicate that the barrier of the first hydrogen abstraction on the high Miller index surface(211) is much lower than those on the(100) and(010) surfaces, and is close to the experimental one. Further dehydrogenation is shown to be difficult and production of 1,5-hexadiene through dimerization of allyl is likely, in agreement with the experimental observations.

Antimony oxides-protected ultrathin Ir-Sb nanowires as bifunctional hydrogen electrocatalysts

Developing electrocatalysts with fast kinetics and long-term stability for alkaline hydrogen oxidation reaction(HOR)and hydrogen evolution reaction(HER)is of considerable importance for the industrial production of green and sustainable energy.Here,an ultrathin Ir-Sb nanowires(Ir-Sb NWs)protected by antimony oxides(SbO_(x))was synthesized as an efficient bifunctional catalyst for both HOR and HER under alkaline media.Except from the much higher mass activities of Ir-Sb nanowires than those of Ir nanowires(Ir NWs)and commercial Pt/C,the SbO_(x) protective layer also contributes to the maintenance of morphology and anti-CO poisoning ability,leading to the long-term cycling performance in the presence of CO.Specifically,the Ir-Sb NW/SbO_(x) exhibits the highest catalytic activities,which are about 3.5 and 4.8 times to those of Ir NW/C and commercial Pt/C toward HOR,respectively.This work provides that the ultrathin morphology and H_(2)O-occupied Sb sites can exert the intrinsic high activity of Ir and effectively optimize the absorption of OH*both in alkaline HER/HOR electrolysis.

过渡金属基材料的可控制备及其电催化醇类氧化研究

氢能作为一种来源丰富、绿色、应用广泛的二次能源,可实现化学能与电能的相互转换,是实现多领域深度清洁脱碳的重要路径,将成为能源转型发展中不可或缺的载体。电解水制氢技术因反应高效、简单易控、无污染等特点而成为研究热点。然而,阳极析氧反应(OER)所需过电位高,反应动力学迟缓,严重制约了电解水制氢的整体效率,因此,使用更易氧化的有机小分子作为阳极添加剂辅助水分解制氢,如电催化醇氧化,不仅可以显著降低水分解制氢的过电势,还能合成绿色高附加值产品。基于此,结合本课题组的研究工作,综述了近年来国内外关于醇类氧化辅助水分解制氢的研究进展,重点探讨了过渡金属催化醇类氧化的反应机理及反应性能、产物选择性和构效关系,并对醇类氧化辅助水分解制氢催化剂所面临的挑战和发展进行展望,旨在为高效的醇类电化学氧化辅助水分解制氢催化剂的合理设计提供指导思想。

金属氧化物半导体一维材料H_(2)S传感器研究进展

金属氧化物半导体具有较好的气敏性,基于金属氧化物半导体H_(2)S气体传感特性得到了广泛研究.然而,随着气体检测精细程度的增加,需要设计具有更优性能的纳米材料,来实现气体传感器检测下限和灵敏度的提高.同其他维度纳米材料相比,一维结构纳米材料由于具有良好的结晶度、较大的比表面积和独特的电子输运特性,在H_(2)S气敏性能提升上有明显优势.因此,本文主要以H_(2)S气体为主体,综述了基于金属氧化物半导体不同一维结构纳米材料的特点和一维结构纳米材料H_(2)S气体传感器的研究进展.讨论了金属氧化物半导体基一维结构纳米材料对H_(2)S气体传感的影响和气敏机理.最后,对金属氧化物半导体基一维结构纳米材料H_(2)S气体传感器的性能改进和未来应用前景进行了展望.

O_3/H_2O_2去除水中硝基苯效果与机理

以硝基苯为目标反应物,对O3/H2O2体系氧化去除水中硝基苯的效果和机理进行了研究,考察了pH值、H2O2剂量、自由基抑制剂或促进剂对硝基苯的去除效果的影响.研究发现,在pH≤7时,H2O2促进臭氧化去除硝基苯的效果较为明显,当H2O2投加量从1.0 mg/L增加到4.0 mg/L时,在氧化5 min内,硝基苯的去除率明显的升高,但当H2O2投加量由4.0 mg/L提高到20 mg/L时,硝基苯的去除率呈下降趋势;同时发现单独臭氧化硝基苯的过程中能明显产生H2O2;几种有机物的加入,不同程度都降低了硝基苯的去除率.无论单独臭氧化还是催化臭氧化都很难将体系TOC大幅度降低,硝基脱出后几乎完全以NO-3形式存在,反应体系pH随氧化时间的增加而明显的降低.LC-MS和GC-MS的分析表明,硝基苯主要的臭氧化产物为酚类和羧酸类物质.对O3/H2O2与硝基苯反应历程进行推导,认为硝基苯的臭氧化降解分为2个阶段,首先是羟基自由基进攻使苯环羟基化,然后是羟基化的芳环发生开裂,生成各种脂肪族化合物或进一步矿化.

超重力反应强化技术最新进展

由于可数量级强化传质和分子混合过程,超重力技术成为最受关注的化工过程强化技术之一。综述了北京化工大学教育部超重力工程研究中心近几年在超重力反应器基础研究及超重力反应强化技术在硫化氢脱除、氧化、卤化等方面的研究进展及工业应用情况,并对超重力反应强化技术的发展趋势进行了展望。

臭氧氧化脱除硫化氢的动力学

本文探讨了臭氧氧化法脱除硫化氢,构建了详细的臭氧氧化硫化氢的反应机理,包含24个物种和74个基元反应.通过臭氧热分解和臭氧低温氧化硫化氢的实验结果进一步验证了本反应机理的可靠性.实验发现,在温度为25℃,物质的量之比为3时,硫化氢的脱除效率达到93%.由模拟结果看出,在停留时间为2s,物质的量之比为1时,氧化最佳温度为150℃—200℃.反应温度为25℃,物质的量之比为1时,把反应时间延长到20s,H2S的脱除率能达到90.9%.

NO_x与NMHC的变化对O_3生成量的影响

利用ＬＬＡ － Ｃ 光化学反应机制， 在 ＮＯｘ 体积分数 φ变化范围很广（１ ．７５ ～３５０ ．０ ，单位为１０ － ９ ，以下同） 的条件下，选择１８ 种ＮＭＨＣ 与ＮＯｘ 的体积分数比（２ ．０ ～２００ ．０） 模拟分析在什么条件下ＮＭＨＣ 的改变对臭氧生成量不大敏感而主要依赖于ＮＯｘ 的大小，同时给出相应条件下ＯＨ 模拟值的变化。结果表明，ＯＨ 峰值均出现在φ（ＮＭＨＣ／ＮＯｘ） ≈８ ．０ 。所找条件是φ（ ＮＯｘ） ≤５０ ．０ 时要求φ（ ＮＭＨＣ／ＮＯｘ） ≥６０ ．０ ； φ（ＮＯｘ） ＞ ５０ ．０ 时需要８ ．０ ≤φ（ＮＭＨＣ／ＮＯｘ） ≤２８ ．０ 。相应Ｏ３ 生成量的最大误差小于２０ ％ 。该条件正适合我国典型污染城市当前φ（ＮＯｘ） 水平和φ（ ＮＭＨＣ／ ＮＯｘ） 范围，可用于我国区域尺度空气质量模拟。与实测资料的对比还有待进一步开展。

脉冲电晕放电处理低浓度硫化氢气体

采用线筒式脉冲电晕反应器对硫化氢气体进行去除,考察了影响硫化氢去除率的主要参数。当气体的停留时间为17s、硫化氢的初始质量浓度约为100mg/m3、峰值电压为48kV时,对硫化氢的去除率接近96%,且增加峰值电压、气体停留时间或气体中的氧气含量可提高硫化氢的去除率。对放电作用下硫化氢的去除动力学进行了研究,并对硫化氢的分解产物进行了初步分析。

常温下硫化氢腐蚀产物的自燃历程

含硫原油加工过程中,H2S腐蚀产物具有很高的自燃性,可以引起火灾和爆炸。根据H2S腐蚀产物的氧化反应产物中单质硫的含量及氧化尾气组成,结合差热-热重分析结果,按氧化程度可以将H2S腐蚀产物氧化自燃过程分为初级、中级和完全氧化3个阶段。在初级氧化阶段,H2S腐蚀产物发生不完全氧化反应,氧化反应温度低于70℃,没有SO2生成;在中级氧化阶段,部分H2S腐蚀产物发生完全氧化反应,氧化反应温度在70～190℃之间,有SO2生成,随着氧化反应温度的升高,发生完全氧化的H2S腐蚀产物的量增加;在完全氧化阶段,H2S腐蚀产物发生完全氧化反应,反应系统内的单质硫被氧化为SO2,氧化反应温度超过190℃。结合氧化反应产物的XRD分析,给出了H2S腐蚀产物在不同氧化自燃阶段发生的化学反应。

硫化氢腐蚀丁腈橡胶的机理

探讨了硫化氢气体及其饱和水溶液对丁腈橡胶性能的影响,采用吉布斯函数验证了硫化氢对丁腈橡胶中残留氧化锌腐蚀的可能性,并通过红外光谱定性和定量分析了硫化氢对丁腈橡胶大分子的腐蚀行为。结果表明,硫化氢的腐蚀会降低丁腈橡胶的物理机械性能;硫化氢气体并不能腐蚀丁腈橡胶中的氧化锌,只有在发生水解后反应才能自发进行;硫化氢气体及其饱和水溶液均能与丁腈橡胶主链中的碳碳双键及侧基氰基发生反应,在硫化氢气体中以双键腐蚀为主,在硫化氢饱和水溶液中则以氰基腐蚀为主,其中腐蚀氰基时为一次加成和二次加成反应。