氨硼烷释氢纳米金属催化剂的研究

化学储氢材料要求具有高的氢存储容量。氨硼烷（NH₃BH₃,AB）的氢含量高达19.6 wt%,是一种具有潜在应用前景的氢存储介质。AB的水解释氢容量高达7.8 wt %,热解释氢则可释放出19.6 wt %的氢,显示出其在化学储氢方面的巨大潜力。在AB释氢研究中,催化剂是研究的核心技术和重要方向。由于纳米催化剂在AB释氢中所表现出的优良催化性能,本文将对氨硼烷释氢纳米金属催化剂及其性能的研究进行全面的总结和展望。     

Rh/N-GMCs纳米催化剂的制备及其催化氨硼烷水解产氢性能研究

本实验通过高温焙烧三聚氰胺和葡萄糖混合物制备出具有独特层状结构的氮掺杂石墨相炭材料(N-GMCs)。再以N-GMCs为载体采用浸渍-还原法将金属Rh负载到载体表面,最终制得Rh/N-GMCs催化剂。结果表明,Rh与NGMCs之间存在强的金属-载体相互作用,Rh的负载量为0.4%时,反应转化频率(TOF)值达到峰值,此时0.4%Rh/NGMCs催化剂的TOF为645.3 min^–1,该催化剂上氨硼烷水解的活化能(E_a)为54.0 k J/mol,氨硼烷脱氢速率随氨硼烷浓度和催化剂浓度呈现正相关,该催化剂循环10次之后,催化活性未明显下降,表明该催化剂具有较好的循环稳定性。     

石墨型氮化碳对氨硼烷放氢性能的影响

利用石墨型氮化碳(C₃N₄)和氨硼烷(NH₃BH₃,AB)球磨制备了AB-C₃N₄体系,发现C₃N₄的加入使AB放氢反应温度明显降低,但是副产物氨气浓度有所升高. 因此,利用LiBH₄改性的C₃N₄(LC₃N₄)同AB球磨合成出了AB-LC₃N₄体系,并采用X射线衍射、程序升温脱附-质谱联用、热重-差热分析及核磁共振等技术考察了该体系的脱氢性能. 结果表明,由于LC₃N₄的加入,AB的放氢反应温度明显降低,放氢反应速率加快,放氢诱导期缩短,同时抑制了副产物无机苯的生成. 另外,C₃N₄的化学修饰也降低了AB-LC₃N₄放氢过程中生成氨气的浓度. 动力学分析和核磁共振结果表明,AB-LC₃N₄分解过程依然遵循NH₃BH₂NH₃BH₄诱导的氨硼烷自分解机理.     

催化氨硼烷水解制氢研究进展

当前,世界范围内的能源利用面临着巨大的挑战,开发绿色洁净能源十分重要。通过水解氨硼烷制备清洁可再生的氢气是解决能源问题的有效途径之一。选择合适的催化剂有效提高制氢效率是氨硼烷水解制氢的关键,开发高效安全的催化剂一直是该领域研究的重点和热点。本文从影响氨硼烷水解制氢反应中催化剂催化性能的因素出发,综述了活性金属组分和载体在催化剂制备过程中以及催化氨硼烷制氢反应中的作用。最后,对催化氨硼烷水解制氢过程所存在的问题以及今后的发展进行了总结和展望。     

氨硼烷催化水解制氢

氢气作为全球公认的清洁能源载体,备受关注。寻找安全高效的储氢材料以转型到氢能社会是当前氢能应用面临最大的挑战之一。氨硼烷(NH₃BH₃,AB)具有非常高的储氢质量分数(19.6 wt%)和体积储氢密度(0.145 kgH₂/L),因其在储氢和放氢性能方面的显著优势,被认为是一种颇具应用潜力的化学储氢材料。氨硼烷能够通过热解、醇解和水解放出氢气。其中,氨硼烷水解制氢可以通过催化剂进行可控放氢,且具有反应条件温和、不产生CO(易使催化剂中毒)等优点,被认为是一种安全高效和实用性强的制氢技术。本文简要介绍了氨硼烷的性质和合成,阐述了氨硼烷水解制氢的机理,综述了近年来氨硼烷水解制氢催化剂的研究进展,分析了碱对氨硼烷水解制氢的促进作用,并讨论了水解产物回收利用问题。     

快速合成廉价CuMo纳米粒子高效催化氨硼烷水解产氢

Noble-metal-free CuMo nanoparticles (NPs) without surfactant or support have been facilely prepared using NaBH₄ as a reducing agent. The as-prepared CuMo nanocatalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area measurements, and used as catalysts for the hydrolysis of ammonia borane (AB, NH₃BH₃) at room temperature. The as-synthesized Cu_0.9Mo_0.1 NPs exhibited a high activity towards the hydrolysis of AB with a turnover frequency (TOF) of 14.9 min^-1, a higher value than that reported for Cu catalysts. Our synthesis is not limited to CuMo NPs alone, but can easily be extended to CuW (3.6 min^-1), CuCr (2 min^-1), NiMo (55.6 min^-1), and CoMo (21.7 min^-1) NPs, providing a general approach to Cu-M (M = Mo, W, Cr) and TM-Mo (TM = Cu, Ni, Co) NPs as a series of novel catalysts for the hydrolysis of AB. The enhanced activity of bimetallic NPs may be attributed to the synergistic effects of the Cu-M NPs induced by the strain and ligand effects.     

离子液体调控合成Pt-Pd双金属纳米材料及其催化氨硼烷水解释氢

在离子液体溴化1-十四烷基-3-甲基咪唑([C₁₄mim]Br)的调控下,以聚乙烯吡咯烷酮(PVP)为稳定剂,在90℃水溶液中一步制备出双金属Pt-Pd纳米材料。通过透射电子显微镜(TEM)、扫描电子显微镜(SEM)、高角度环形暗场扫描透射电镜(HAADF-STEM)、X射线能谱(EDS)、X射线衍射仪(XRD)和X射线光电子能谱(XPS)等对产物的形貌、结构、组成和价态等进行了详细的表征分析。结果表明,除了纯Pd样品,其它比例的Pt-Pd纳米材料均具有多孔结构。离子液体对多孔Pt-Pd纳米材料的调控起到了重要作用,对于[C_nmim]Br离子液体,当烷基侧链长≥C12时,有利于形成多孔的Pd@Pt核壳球形结构。在氨硼烷水解释氢实验中,不同比例的Pt-Pd双金属纳米材料均表现出优于商用Pd/C的催化活性。其中,Pt₃Pd₇纳米材料具有最优的催化性能,催化过程在6 min内完成,产氢率高达100%。氨硼烷水解释氢的活化能(E_a)为36.15 kJ/mol,周转频率(TOF)为35....     

金属-有机骨架材料在催化氨硼烷水解释氢中的研究进展

当前,化石燃料的大量消耗和对能源日益增长的需求推动了可再生和高效能源材料的开发。氢因丰富的来源以及清洁的特性而被视为潜在的能源载体。通过水解氨硼烷制备清洁可再生的氢气是解决能源问题的有效途径之一。开发高效安全的催化剂一直是该领域研究的重点和热点。金属-有机骨架材料（MOFs）因其独特的结构、组成和特性,在氨硼烷水解制氢中有广泛的应用。本文以MOFs材料在催化剂设计制备中的作用为侧重点,综述了不同MOFs材料在催化氨硼烷水解制氢反应中的作用,对其在催化氨硼烷水解制氢应用过程中所存在的问题和今后的发展进行了总结和展望。     

多孔碳负载镍纳米颗粒的制备及催化氨硼烷水解制氢

合成了蜂窝状的分级多孔碳,并以多孔碳为载体通过浸渍-化学还原法制备碳载镍(Ni/C)作为催化氨硼烷水解制氢的催化剂。采用XRD、BET、SEM、Raman、TEM等手段对样品进行了表征并研究了Ni/C室温催化性能。结果显示,多孔碳比表面积高达737 m2·g-1,具有部分石墨化结构;负载的非晶态镍纳米颗粒平均粒径约为10 nm,均匀分布在碳基材。碳载镍对氨硼烷水解反应具有良好的催化活性,镍负载量为30wt%时催化性能最佳,298 K温度下放氢速率达到1 304.67 m L·min-1·g-1,活化能为29.1 k J·mol-1,并且具备一定的催化稳定性,表明Ni/C可作为一种廉价高效的催化剂应用于催化氨硼烷水解制氢。     

多孔碳负载镍纳米颗粒的制备及催化氨硼烷水解制氢

合成了蜂窝状的分级多孔碳,并以多孔碳为载体通过浸渍-化学还原法制备碳载镍(Ni/C)作为催化氨硼烷水解制氢的催化剂。采用XRD、BET、SEM、Raman、TEM等手段对样品进行了表征并研究了Ni/C室温催化性能。结果显示,多孔碳比表面积高达737 m²·g^-1,具有部分石墨化结构;负载的非晶态镍纳米颗粒平均粒径约为10 nm,均匀分布在碳基材。碳载镍对氨硼烷水解反应具有良好的催化活性,镍负载量为30wt%时催化性能最佳,298 K温度下放氢速率达到1 304.67 mL·min^-1·g^-1,活化能为29.1 kJ·mol^-1,并且具备一定的催化稳定性,表明Ni/C可作为一种廉价高效的催化剂应用于催化氨硼烷水解制氢。     

Production of Dihydrogen Using Ammonia Borane as Reagent and Pyrazole as Catalyst

Theoretical chemistry (DLPNO-CCSD(T)/def2-TZVP//M06-2x/aug-cc-pVDZ) was used to design a system based on ammonia boranes catalyzed by pyrazoles with the aim of producing dihydrogen, nowadays of high interest as clean fuel. The reactivity of ammonia borane and cyclotriborazane were investigated, including catalytic activation through 1H-pyrazole, 4-methoxy-1H-pyrazole, and 4-nitro-1H-pyrazole. The results point toward a catalytic cycle by which, at the same time, ammonia borane can initially store and then, through catalysis, produce dihydrogen and amino borane. Subsequently, amino borane can trimerize to form cyclotriborazane that, in presence of the same catalyst, can also produce dihydrogen. This study proposes therefore a consistent progress in using environmentally sustainable (metal free) catalysts to efficiently extract dihydrogen from small B−N bonded molecules.     

Theoretical Study of Hydrogen Production from Ammonia Borane Catalyzed by Metal and Non-Metal Diatom-Doped Cobalt Phosphide

The decomposition of ammonia borane (NH₃BH₃) to produce hydrogen has developed a promising technology to alleviate the energy crisis. In this paper, metal and non-metal diatom-doped CoP as catalyst was applied to study hydrogen evolution from NH₃BH₃ by density functional theory (DFT) calculations. Herein, five catalysts were investigated in detail: pristine CoP, Ni- and N-doped CoP (CoP_Ni-N), Ga- and N-doped CoP (CoP_Ga-N), Ni- and S-doped CoP (CoP_Ni-S), and Zn- and S-doped CoP (CoP_Zn-S). Firstly, the stable adsorption structure and adsorption energy of NH₃BH₃ on each catalytic slab were obtained. Additionally, the charge density differences (CDD) between NH₃BH₃ and the five different catalysts were calculated, which revealed the interaction between the NH₃BH₃ and the catalytic slab. Then, four different reaction pathways were designed for the five catalysts to discuss the catalytic mechanism of hydrogen evolution. By calculating the activation energies of the control steps of the four reaction pathways, the optimal reaction pathways of each catalyst were found. For the five catalysts, the optimal reaction pathways and activation energies are different from each other. Compared with undoped CoP, it can be seen that CoP_Ga-N, CoP_Ni-S, and CoP_Zn-S can better contribute hydrogen evolution from NH₃BH₃. Finally, the band structures and density of states of the five catalysts were obtained, which manifests that CoP_Ga-N, CoP_Ni-S, and CoP_Zn-S have high-achieving catalytic activity and further verifies our conclusions. These results can provide theoretical references for the future study of highly active CoP catalytic materials.     

纳米晶态硼化钴的合成及其催化氨硼烷高效制氢

采用简单的煅烧工艺合成了纳米硼化钴(CoB)晶体,并首次研究了纳米CoB晶体在氨硼烷溶液水解制氢过程中的催化活性。研究发现,纳米CoB晶体具有较高的催化活性,在室温条件下其转换频率(TOF)为35.3 mol_H2·mol_cat^-1·min^-1,优于同等条件下贵金属Pt催化剂(TOF=29.3 mol_H2·mol_cat^-1·min^-1)。此外,循环测试8次后纳米硼化物晶体的催化制氢性能没有发生衰减。进一步研究发现CoB表面的Co⁰物种是催化制氢的活性位点,而表面的B物种位点能够有效辅助Co⁰位点实现协同催化氨硼烷制氢。     

纳米晶态硼化钴的合成及其催化氨硼烷高效制氢

采用简单的煅烧工艺合成了纳米硼化钴(CoB)晶体,并首次研究了纳米CoB晶体在氨硼烷溶液水解制氢过程中的催化活性。研究发现,纳米CoB晶体具有较高的催化活性,在室温条件下其转换频率(TOF)为35.3mol_H2·mol_cat^-1·min^-1,优于同等条件下贵金属Pt催化剂(TOF=29.3mol_H2·mol_cat^-1·min^-1)。此外,循环测试8次后纳米硼化物晶体的催化制氢性能没有发生衰减。进一步研究发现CoB表面的Co⁰物种是催化制氢的活性位点,而表面的B物种位点能够有效辅助Co⁰位点实现协同催化氨硼烷制氢。     

Synthesis of Ammonia Borane Nanoparticles and the Diammoniate of Diborane by Direct Combination of Diborane and Ammonia

Pure nanoparticle ammonia borane (NH₃BH₃, AB) was first prepared through a solvent‐free, ambient‐temperature gas‐phase combination of B₂H₆ with NH₃. The prepared AB nanoparticle exhibits improved dehydrogenation behavior giving 13.6 wt. % H₂ at the temperature range of 80–175 °C without severe foaming. Ammonia diborane (NH₃BH₂(μ‐H)BH₃, AaDB) is proposed as the intermediate in the reaction of B₂H₆ with NH₃ based on theoretical studies. This method can also be used to prepare pure diammoniate of diborane ([H₂B(NH₃)₂][BH₄], DADB) by adjusting the ratio and concentration of B₂H₆ to NH₃.     

CuCo/BNNSs纳米催化剂对固态储氢材料氨硼烷水解的催化性能

采用共还原法将CuCo双金属负载到通过聚乙烯吡咯烷酮(PVP)辅助离子插层法制备的少层氮化硼纳米片(BNNSs)上,获得了平均粒径为2.7 nm且高度分散的铜钴/氮化硼纳米片(CuCo/BNNSs)纳米催化剂。通过原子力显微镜(AFM)、X射线衍射(XRD)、傅里叶转换红外光谱(FTIR)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和高分辨率透射电镜(HRTEM)对载体及催化剂的结构及形貌进行表征,并研究了CuCo/BNNSs的催化性能。研究发现,由于Cu、Co、BNNSs和OH-之间高效的四重效应协同使得Cu0.5Co0.5/BNNSs纳米催化剂在室温、pH=14条件下对氨硼烷(AB,NH3BH3)水解释氢具有极高的催化活性。转化频率(TOF)值达到104.52 molH2·molmetal^-1·min^-1,且CuCo/BNNSs纳米催化剂具有良好的稳定性,6次循环利用后仍保持较高催化活性。