In situ formation of multiple catalysts for enhancing the hydrogen storage of MgH_(2) by adding porous Ni_(3)ZnC_(0.7)/Ni loaded carbon nanotubes microspheres

MgH_(2) is considered one of the most promising hydrogen storage materials because of its safety,high efficiency,high hydrogen storage quantity and low cost characteristics.But some shortcomings are still existed:high operating temperature and poor hydrogen absorption dynamics,which limit its application.Porous Ni_(3)ZnC_(0.7)/Ni loaded carbon nanotubes microspheres(NZC/Ni@CNT)is prepared by facile filtration and calcination method.Then the different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%)is added to the MgH_(2) by ball milling.Among the three samples with different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%),the MgH_(2)-5 wt%NZC/Ni@CNT composite exhibits the best hydrogen storage performances.After testing,the MgH_(2)-5 wt%NZC/Ni@CNT begins to release hydrogen at around 110℃ and hydrogen absorption capacity reaches 2.34 wt%H_(2) at 80℃ within 60 min.Moreover,the composite can release about 5.36 wt%H_(2) at 300℃.In addition,hydrogen absorption and desorption activation energies of the MgH_(2)-5 wt%NZC/Ni@CNT composite are reduced to 37.28 and 84.22 KJ/mol H_(2),respectively.The in situ generated Mg_(2)NiH_(4)/Mg_(2)Ni can serve as a"hydrogen pump"that plays the main role in providing more activation sites and hydrogen diffusion channels which promotes H_(2) dissociation during hydrogen absorption process.In addition,the evenly dispersed Zn and MgZn2 in Mg and MgH_(2) could provide sites for Mg/MgH_(2) nucleation and hydrogen diffusion channel.This attempt clearly proved that the bimetallic carbide Ni_(3)ZnC_(0.7) is a effective additive for the hydrogen storage performances modification of MgH_(2),and the facile synthesis of the Ni_(3)ZnC_(0.7)/Ni@CNT can provide directions of better designing high performance carbide catalysts for improving MgH_(2).

Defect engineering of high-loading single-atom catalysts for electrochemical carbon dioxide reduction

Electrochemical carbon dioxide reduction reaction(CO_(2)RR)provides an attractive approach to carbon capture and utilization for the production high-value-added products.However,CO_(2)RR still suffers from poor selectivity and low current density due to its sluggish kinetics and multitudinous reaction pathways.Single-atom catalysts(SACs)demonstrate outstanding activity,excellent selectivity,and remarkable atom utilization efficiency,which give impetus to the search for electrocatalytic processes aiming at high selectivity.There appears significant activity in the development of efficient SACs for CO_(2)RR,while the density of the atomic sites remains a considerable barrier to be overcome.To construct high-metal-loading SACs,aggregation must be prevented,and thus novel strategies are required.The key to creating high-density atomically dispersed sites is designing enough anchoring sites,normally defects,to stabilize the highly mobile separated metal atoms.In this review,we summarized the advances in developing high-loading SACs through defect engineering,with a focus on the synthesis strategies to achieve high atomic site loading.Finally,the future opportunities and challenges for CO_(2)RR in the area of high-loading single-atom electrocatalysts are also discussed.

Synthesis of glycerin triacetate over molding zirconia-loaded sulfuric acid catalyst

Zirconia-loaded sulfuric acid （SO2-/ZrO2） catalysts were prepared by impregnation method, molded by punch tablet machine and characterized by X-ray diffraction. SO4^2-/ZrO2 catalyst was used to obtain glycerol triacetate （GTA） directly from glycerin. The effect of some factors, such as different temperatures of calcination and catalysts molded or not, on the reusable times of catalysts and the yield of GTA were investigated. The optimum reaction conditions were shown as follows： the reaction temperature was 403 K; the reaction time continued for 8 h; the amount of molded catalysts was 5 wt% of glycerin and the molar ratio of glycerin to acetic acid was 1 ： 8. The yield of GTA was 97.93% under the optimum condition.

Effect of Sr loading on oxydehydrogenation of propane to propylene over Al_2O_3-supported V-Mo catalysts

Incorporation of strontium into V-Mo alumina-supported catalyst enhanced its performance (increased conversion and selectivity,decreased reducibility and improved stability) in propane oxydehydrogenation to propylene.12.5% Sr loading was shown to be the optimum content to the V-Mo catalyst.The results were supported by various characterization techniques,namely,BET,XRD,SEM,FTIR and TPD.

High-loading Pt-alloy catalysts for boosted oxygen reduction reaction performance

To improve performance of membrane electrode assembly(MEA)at large current density region,efficient mass transfer at the cathode is desired,for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon.But the high loading may induce unwanted par-ticle aggregation.In this work,H-PtNi/C with 33%(mass)Pt loading on carbon and monodisperse distri-bution of 3.55 nm PtNi nanoparticles,was prepared by a bimodal-pore route.In electrocatalytic oxygen reduction reaction(ORR),H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C(13.3%(mass))in the half-cell.While in H_(2)-0_(2) MEA,H-PtNi/C delivers the peak power density of 1.51 W·cm^(-2) and the mass transfer limiting current density of 4.4 A·cm^(-2),being 21%and 16%higher than those of L-PtNi/C(1.25 W·cm^(-2),3.8 A·cm^(-2))respectively,which can be ascribed to enhanced mass trans-fer brought by the thinner catalyst layer in the former.In addition,the same method can be used to pre-pare PtFe alloy catalyst with a high-Pt loading of 36%(mass).This work may lead to a range of catalyst materials for the large current density applications,such as fuel cell vehicles.

Study on Relationship between Microstructure of Active Phase and HDS Performance of Sulfided Ni-Mo Catalysts: Effect of Metal Loading

Six Ni-Mo catalysts with different metal contents were prepared and characterized by N2 adsorption and X-ray diffractometry. The active phase microstructure of these catalysts was examined by the Raman spectroscopy, temperatureprogrammed reduction(TPR), X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Hydrodesulfurization(HDS) activity of catalyst samples were analyzed in a flow fixed-bed microreactor. The sulfidation degree of Mo and the length of the MoS2 slab slightly increased with the amount of metal loaded following sulfidation. This small change is attributed to polymolybdate species observed in all the oxidized catalysts. Weak metal-support interactions, as determined by the TPR technique, increased the NiSx sulfidation phase and MoS2 slab stacking. The HDS activity of the catalyst samples increased with the number of active sites. For high metal loading catalysts, their HDS activity was nearly identical because the sulfur atoms cannot easily approach active sites. This change is caused by the large number of stacked layers in the MoS2 slabs as well as the decrease in the specific surface area and pore volume of the catalyst samples with an increasing metal loading.

High-performance proton exchange membrane fuel cell with ultra-low loading Pt on vertically aligned carbon nanotubes as integrated catalyst layer

Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.

Electrochemically Grown Ultrathin Platinum Nanosheet Electrodes with Ultralow Loadings for Energy-Saving and Industrial-Level Hydrogen Evolution

Nanostructured catalyst-integrated electrodes with remarkably reduced catalyst loadings,high catalyst utilization and facile fabrication are urgently needed to enable cost-effective,green hydrogen production via proton exchange membrane electrolyzer cells(PEMECs).Herein,benefitting from a thin seeding layer,bottom-up grown ultrathin Pt nanosheets(Pt-NSs)were first deposited on thin Ti substrates for PEMECs via a fast,template-and surfactant-free electrochemical growth process at room temperature,showing highly uniform Pt surface coverage with ultralow loadings and vertically well-aligned nanosheet morphologies.Combined with an anode-only Nafion 117 catalyst-coated membrane(CCM),the Pt-NS electrode with an ultralow loading of 0.015 mgPt cm−2 demonstrates superior cell performance to the commercial CCM(3.0 mgPt cm^(−2)),achieving 99.5%catalyst savings and more than 237-fold higher catalyst utilization.The remarkable performance with high catalyst utilization is mainly due to the vertically well-aligned ultrathin nanosheets with good surface coverage exposing abundant active sites for the electrochemical reaction.Overall,this study not only paves a new way for optimizing the catalyst uniformity and surface coverage with ultralow loadings but also provides new insights into nanostructured electrode design and facile fabrication for highly efficient and low-cost PEMECs and other energy storage/conversion devices.

γ-Mo_(2)N/C催化剂的合成及其甲酸脱氢性能研究

甲酸(FA)因其H含量较高(4.4%)、易产H_(2)、可经小平台化合物合成等优势受到广泛关注,而γ-Mo_(2)N/C对FA沿H_(2)和CO_(2)路径分解具有非常高的选择性,产生CO极少,显示出较高的应用价值。基于此,本研究采用对苯二胺和钼酸铵水溶液经前驱体制备γ-Mo_(2)N/C催化剂,并对其FA分解性能进行了原位评价,采用热重分析(TG)、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)等表征手段对催化剂的结构和表面官能团进行了分析,利用DFT对FA在γ-Mo_(2)N (200)晶面的吸附构型进行了计算,在此基础上,对催化剂性能及FA在其表面的分解机理进行了研究。结果表明,γ-Mo_(2)N/C在较低温度下即可表现出极高的催化活性,提高γ-Mo_(2)N在C载体上的分散性能有效改善FA转化率。对苯二胺与钼酸铵的物质的量比为4∶1时,催化性能最佳,在160℃、100 h的FA分解实验中,催化剂性能稳定、H_(2)选择性高(N_(2)40 mL/min, CO<5.0×10^(-5))。而DFT计算表明,FA中O-H键的H原子与γ-Mo_(2)N/C (200)晶面上N原子结合的可能性更大,而C=O键的O原子更有可能与γ-Mo_(2)N/C (200)晶面上Mo原子结合。上述结果有助于明确FA在γ-Mo_(2)N/C作用下的分解机理,也显示出非贵金属催化剂γ-Mo_(2)N/C在FA分解制H_(2)方面潜在的应用前景。

贵金属催化剂低温催化氧化一氧化碳研究进展

随着“双碳”政策的不断推行以及人们环保意识的不断提高,一氧化碳(CO)作为典型的大气污染物,已成为工业废气和汽车尾气排放的主要控制对象。贵金属型CO氧化催化剂具有优异的低温活性、抗中毒抗性能,是CO催化氧化处理的最为有效的手段之一。基于贵金属型CO氧化催化剂的研究现状,重点围绕Pt、Pd、Au、Ag、Rh贵金属催化剂的贵金属调控技术和载体可控技术进行综述,总结了贵金属型CO氧化催化剂的性能优化策略和发展方向,为开发高性能的CO氧化催化剂提供指导。

Effect of catalyst diesel particulate filter aging and catalyst loadings on particulate emission characteristics from a diesel vehicle

In this study,the effect of new and used catalyzed diesel particulate filter(CDPF)with different catalyst loadings on the particulate emissions including the particle mass(PM),particle number(PN),particle size distribution(PSD)and geometric mean diameter(GMD)from a diesel vehicle were investigated based on a heavy chassis dynamometer.Results showed that more than 97.9%of the PN and 95.4%of the PM were reduced by the CDPF,and the reduction efficiency was enhanced by the catalyst loading.After using the CDPF,the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size,more nucleation mode particles were reduced compared with accumulation mode ones,but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst loading.Notably,the CDPF increased the accumulation mode particles proportion,producing a larger GMD.For the used CDPF,its reduction effect on the particulate emissions enhanced,especially for the PM in accumulation mode.The PSD returned to bimodal,but the peak at accumulation mode began to be higher than that at nucleation mode,illustrating that more nucleation mode particles was removed.The aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD,but the effect of catalyst loading on the PN and PM emission factors was weakened.The used CDPF further increased the GMD,and the effect of catalyst loading on the GMD was strengthened,a higher catalyst loading led to a reduction in the GMD.

分步负载金属法制备铁钴双金属位点高效氧还原电催化剂

过渡金属和氮掺杂的碳(M-N-C)由于优异的电催化活性以及较低的生产成本,成为铂基催化剂的替代。然而,目前的M-N-C催化剂通常涉及金属盐、含氮物质和碳载体的结合,在经过热处理和酸洗过程后得到的催化剂在活性位点密度和传质能力上性能不足。采用分步负载金属法制备了Fe、Co双金属掺杂的M-N-C催化剂。利用Zn2+和Co2+的竞争效应,成功合成了小尺寸且均匀的Zn-Co-ZIFs双金属沸石咪唑骨架。随后,在不形成金属团簇的前提下将最大量的Fe原子嵌入C-Zn-Co-ZIFs-H+前体结构中,使其在热解后能产生大量的FeCo—Nx活性位点。这种改进显著增加了FeCo-N-C-2催化剂中Fe活性位点的含量(1.9%,质量分数),并深度优化了其微孔和介孔结构(860 m^(2)·g^(-1))。该催化剂在0.1 mol·L^(-1) HClO_(4)和0.1 mol·L^(-1) KOH溶液中,氧还原反应(ORR)活性展现出了0.806 V和0.921 V的半波电位,并分别在50000、45000 s恒定电位测试后保持了91.21%和95.32%的活性。将其组装于质子交换膜燃料电池(PEMFCs)和碱性锌-空气液流电池(ZAFBs)中,峰值功率密度分别达到了746、164 mW·cm^(-2),显示出优越的性能。

Fe@CeO_(2)/CN双空腔核壳磁性载金椭球催化剂及其催化还原对硝基苯酚和染料污染物

载金催化剂可在温和条件下还原性降解环境中某些有毒有害污染物,并转化为低毒性、高附加值的物质,从而促进水体污染物化学资源转化和综合利用.本文设计制备Fe@CeO_(2)/CN双空腔核壳磁性载金椭球催化剂,用于还原降解水体中对硝基苯酚和染料污染物.该催化剂先制备Fe_(2)O_(3)@CeO_(2)梭型微粒内核,采用乙二胺介导的Stober扩展法在其表面合成SiO_(2)@RF复合物,经过碳化-水热蚀刻得到具有介孔碳氮壳层的Fe_(2)O_(3)@CeO_(2)/CN椭球;采用[Au(en)_(2)]^(3+)为金前驱体的沉积沉淀-还原气氛热处理法在上述椭球中构筑较好分散度超细纳米Au颗粒,同时Fe_(2)O_(3)转化为小体积Fe颗粒并形成内空腔,得到Fe@CeO_(2)-Au/CN双空腔核壳磁性椭球催化剂.该催化剂独特的结构特征和复合组分协同增强性效应使其在还原降解对硝基苯酚和染料污染物中均表现优越的催化反应性能和循环使用性能,重复多次使用后仍保存良好的磁分离性和较好的结构完整性.

基于分子筛的低负载金属催化剂在绿色化学中的应用

为探究有效的绿色催化剂,制备了基于分子筛的低负载金属催化剂,并在催化氢硅烷水解实验和循环实验中验证了其效用。实验结果显示,在600℃条件下制备的基于分子筛的低负载钯金属催化剂最高具有93%的产出率,再生后循环使用仍具有高至75%的产出率,是高产出的氢硅烷水解催化剂,具有良好的催化活性且可循环使用,符合绿色化学的概念。

RK-05型甲醇合成催化剂的工业应用

简单介绍了甲醇合成工艺流程,从单位体积催化剂甲醇产量、生产负荷、合成塔压差、床层温度、转化率五个方面介绍了两批RK-05型甲醇合成催化剂的工业应用情况,结果表明:RK-05型甲醇合成催化剂在使用的初期、中期阶段具有床层温度分布均匀、生产负荷稳步提升、催化剂转化率比较稳定、甲醇产量较好等特点。

CoNi nanoparticles anchored inside carbon nanotube networks by transient heating:Low loading and high activity for oxygen reduction and evolution

Transitional metal alloy and compounds have been developed as the low cost and efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).However,a high mass loading of these catalysts is commonly needed to achieve acceptable catalytic performance,which could cause such problems as battery weight gain,mass transport blocking,and catalyst loss.We report herein the preparation of fine CoNi nanoparticles(5-6 nm)anchored inside a nitrogendoped defective carbon nanotube network(CoNi@N-DCNT)by a transient Joule heating method.When utilized as an electrocatalyst for oxygen reduction and evolution in alkaline media,the CoNi@N-DCNT film catalyst with a very low mass loading of 0.06 mg cm^(-2) showed excellent bifunctional catalytic performance.For ORR,the onset potential(Eonset)and the half-wave potential(E_(1/2))were 0.92 V versus reversible hydrogen electrode(vs.RHE)and 0.83 V(vs.RHE),respectively.For OER,the potential at the current density(J)of 10 mA cm^(-2)(E_(10))was 1.53 V,resulting in an overpotential of 300 mV much lower than that of the commercial RuO_(2) catalyst(320 mV).The potential gap between E_(1/2) and E_(10) was as small as 0.7 V.Considering the low mass loading,the mass activity at E_(10) reached at 123.2 A g^(-1),much larger than that of the RuO_(2) catalyst and literature results of transitional metal-based bifunctional catalysts.Moreover,the CoNi@N-DCNT film catalyst showed very good long-term stability during the ORR and OER test.The excellent bifunctional catalytic performance could be attributed to the synergistic effect of the bimetal alloy.

Study and Commercial Application of Graded Optimization of Catalysts for Fixed Bed Residue Upgrading Unit

反的催化剂装载的 SHIFT-G 技术被用来优化在对待联合起来的残余水疗院分级的催化剂。结果，从飞行员测试和商业单位拿，证明了相当分级系统罐头的优化催化剂散布反应负担，有效地改进水疗院的性质对待的产品，延长操作周期并且支持经济好处。

Effect of catalyzed diesel particulate filter and its catalyst loading on emission characteristics of a non-road diesel engine

In this study, the effects of a diesel oxidation catalyst(DOC) coupled with a catalyzed diesel particulate filter(CDPF) with different catalyst loadings on the power, fuel consumption,gaseous and particulate emissions from a non-road diesel engine were investigated. Results showed that the after-treatment had a negligible effect on the power and fuel consumption.The reduction effect of the DOC on the CO and hydrocarbon(HC) increased with the engine load. Further reductions occurred coupling with the CDPF. Increasing the catalyst loading resulted in a more significant reduction in the HC emissions than CO emissions. The DOC could increase the NO_(2)proportion to 37.9%, and more NO_(2)was produced when coupled with the CDPF below 250℃;above 250℃, more NO_(2)was consumed. The after-treatment could reduce more than 99% of the particle number(PN) and 98% of the particle mass(PM).Further reductions in the PN and PM occurred with a higher CDPF catalyst loading. The DOC had a better reduction effect on the nucleation particles than the accumulation ones, but the trend reversed with the CDPF. The DOC shifted the particle size distribution(PSD) to larger particles with an accumulation particle proportion increasing from 13% to 20%, and the geometric mean diameter(GMD) increased from 18.2 to 26.0 nm. The trend reversed with the CDPF and the accumulation particle proportion declined to less than 10%. A lower catalyst loading on the CDPF led to a higher proportion of nucleation particles and a smaller GMD.

不同载体Pt基整体式催化剂对氢气低温反应性能的影响

以H型分子筛-5(hydrogen zeolite sieve molecular-5,HZSM-5)和氧化物(Al_(2)O_(3)、TiO_(2)和SiO_(2))涂层为载体、堇青石蜂窝陶瓷为基体、贵金属铂(Pt)为活性组分,制备了Pt/载体/堇青石整体式催化剂.利用XRD、SEM、TEM和XPS等表征手段,对催化剂的结构与性质进行了分析.探讨了在氢气体积分数为2.5%的环境中,不同载体、不同Pt负载量对氢气低温催化燃烧反应性能的影响.研究结果表明:以HZSM-5为载体的整体式催化剂性能最优,这与催化剂活性层黏结性良好、Pt在该载体上的分布良好及其粒径均匀有关;以SiO_(2)为载体的催化剂性能最差,测试显示这种载体上Pt 0种类含量最少,且Pt负载不牢;Pt负载量为0.01 g·L^(-1)时,Pt/HZSM-5/堇青石整体式催化剂的催化活性较好;Pt负载量为0.05 g·L^(-1)及以上时,整体式催化剂均能在室温下快速起燃,并实现氢气转化率为100%.

PEMFC阴极催化层氧传质阻力影响的研究进展

质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)阴极催化层的氧传质阻力是限制高电流密度下低Pt载量膜电极极化性能的主要瓶颈。研究如何降低阴极催化层氧传质阻力对于提高PEMFC的性能、加快其商业化应用至关重要。本文首先分析了催化层氧传质阻力产生的根源及构成,指出氧气穿越气相、离聚物、Pt纳米粒子三相接触界面时产生的局部氧传质阻力是其重要部分;接着从Pt纳米粒子、离聚物、碳载体和水这四方面阐述了各因素对氧传质阻力特别是局部氧传质阻力的影响,归纳总结了降低氧传质阻力的方法;最后对低Pt载量PEMFC阴极催化层设计进行了展望,提出从构建适宜的载体孔结构、合理分布孔道内外Pt粒子数量、控制离聚物厚度及分布,以及强化水转移等方面着手,以降低氧传质阻力,提高电池在高电流密度下的功率输出。