First-principles analysis of the structural,electronic, and elastic properties of cubic organic-inorganic perovskite HC(NH_2)_2PbI_3

The structural, electronic, and elastic properties of cubic HC(NH_2)_2PbI_3 perovskite are investigated by density functional theory using the Tkatchenko–Scheffler pairwise dispersion scheme. Our relaxed lattice parameters are in agreement with experimental data. The hydrogen bonding between NH_2 and I ions is found to have a crucial role in FAPbI_3 stability. The first calculated band structure shows that HC(NH_2)_2PbI_3 has a direct bandgap(1.02 eV) at R-point, lower than the bandgap(1.53 eV) of CH_3NH_3PbI_3. The calculated density of states reveals that the strong hybridization of s(Pb)–p(I) orbital in valence band maximum plays an important role in the structural stability. The photo-generated effective electron mass and hole mass at R-point along the R–Γ and R–M directions are estimated to be smaller: m_e~*= 0.06 m0 and m_h~*= 0.08 m0 respectively, which are consistent with the values experimentally observed from long range photocarrier transport. The elastic properties are also investigated for the first time, which shows that HC(NH_2)_2PbI_3 is mechanically stable and ductile and has weaker strength of the average chemical bond. This work sheds light on the understanding of applications of HC(NH_2)_2PbI_3 as the perovskite in a planar-heterojunction solar cell light absorber fabricated on flexible polymer substrates.     

Oxygen vacancies and V co-doped Co_3O_4 prepared by ion implantation boosts oxygen evolution catalysis

Introducing heteroatoms and defects is a significant strategy to improve oxygen evolution reaction(OER) performance of electrocatalysts. However, the synergistic interaction of the heteroatom and defect still needs further investigations. Herein, we demonstrated an oxygen vacancy-rich vanadium-doped Co_3O_4(V–O_v–Co_3O_4), fabricated by V-ion implantation, could be used for high-efficient OER catalysis. X-ray photoelectron spectra(XPS) and density functional theory(DFT) calculations show that the charge density of Co atom increased, and the reaction barrier of reaction pathway from O*to HOO*decreased. V–O_v–Co_3O_4 catalyst shows a low overpotential of 329 mV to maintain current density of 10 m A·cm~(-2), and a small Tafel slope of 74.5 m V·dec~(-1). This modification provides us with valuable perception for future design of heteroatom-doped and defect-based electrocatalysts.     

Theoretical investigation of CoTa2O6/graphene heterojunctions for oxygen evolution reaction

Water electrolysis is to split water into hydrogen and oxygen using electricity as the driving force. To obtain low-cost hydrogen in a large scale, it is critical to develop electrocatalysts based on earth abundant elements with a high efficiency. This computational work started with Cobalt on CoTa₂O₆ surface as the active site, CoTa₂O₆/Graphene heterojunctions have been explored as potential oxygen evolution reaction (OER) catalysts through density functional theory (DFT). We demonstrated that the electron transfer (δ) from CoTa₂O₆ to graphene substrate can be utilized to boost the reactivity of Co-site, leading to an OER overpotential as low as 0.30 V when N-doped graphene is employed. Our findings offer novel design of heterojunctions as high performance OER catalysts.     

Enhancing the photo-luminescence stability of CH3NH3PbI3 film with ionic liquids

The methylammonium lead triiodide (CH₃NH₃PbI₃)-based perovskite shows a great alluring prospect in areas of solar cells, lasers, photodetectors, and light emitting diodes owing to their excellent optical and electrical advantages. However, it is very sensitive to the surrounding oxygen and moisture, which limits its development seriously. It is urgent to spare no effort to enhance its optical and electrical stability for further application. In this paper, we synthesize the MAPbI₃ perovskite film on the glass substrate with/without the ionic liquid (IL) of 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) by a simple two-step sequential solution method. The additive of BMIMBF₄ can improve the quality of crystal structure. Moreover, the photo-luminescence (PL) intensity of MAPbI₃ film with BMIMBF₄ is much stronger than the pure MAPbI₃ film after a week in the air, which is almost ten-fold of the pure one. Meanwhile, under the illumination of 405-nm continuous wave (CW) laser, the fluorescent duration of the MAPbI₃ film with BMIMBF₄ is approximately 2.75 min, while the pure MAPbI₃ film is only about 6 s. In fact, ionic liquid of BMIMBF₄ in the perovskite film plays a role of passivation, which prevents the dissolution of MAPbI₃ into CH₃NH₃ and PbI₂ and thus enhances the stability of environment. In addition, the ionic liquid of BMIMBF₄ possesses high ionic conductivity, which accelerates the electron transport, so it is beneficial for the perovskite film in the areas of solar cells, photodetectors, and lasers. This interesting experiment provides a promising way to develop the perovskite's further application.     

蓝宝石R面上ZnO薄膜的NH3掺杂研究

以NH₃为掺杂源,利用金属有机化学气相沉积(MOCVD)系统在蓝宝石R面上生长出掺氮ZnO薄膜。通过XRD,SEM测量优化了其生长参数,在610℃和在80sccm的NH₃流量下生长出了〈1120〉单一取向的ZnO薄膜。经Hall电阻率测量,得知该薄膜呈现弱p型或高电阻率,并对其光电子能谱进行了研究。     

Device simulation of lead-free CH_3NH_3SnI_3 perovskite solar cells with high efficiency

The lead-free perovskite solar cells(PSCs) have drawn a great deal of research interest due to the Pb toxicity of the lead halide perovskite.CH_3NH_3SnI_3 is a viable alternative to CH_3NH_3PbX_3,because it has a narrower band gap of 1.3 eV and a wider visible absorption spectrum than the lead halide perovskite.The progress of fabricating tin iodide PSCs with good stability has stimulated the studies of these CH_3NH_3SnI_3 based cells greatly.In the paper,we study the influences of various parameters on the solar cell performance through theoretical analysis and device simulation.It is found in the simulation that the solar cell performance can be improved to some extent by adjusting the doping concentration of the perovskite absorption layer and the electron affinity of the buffer and HTM,while the reduction of the defect density of the perovskite absorption layer significantly improves the cell performance.By further optimizing the parameters of the doping concentration(1.3 × 10~(16) cm~3) and the defect density(1 × 10~(15) cm~3) of perovskite absorption layer,and the electron affinity of buffer(4.0 eV) and HTM(2.6 eV),we finally obtain some encouraging results of the J_(sc) of 31.59 mA/cm~2,V_(oc) of 0.92 V,FF of 79.99%,and PCE of 23.36%.The results show that the lead-free CH_3NH_3SnI_3 PSC is a potential environmentally friendly solar cell with high efficiency.Improving the Sn~(2+) stability and reducing the defect density of CH_3NH_3SnI_3 are key issues for the future research,which can be solved by improving the fabrication and encapsulation process of the cell.     

纳米CeO2-xNx固溶体的光谱特征对其催化性能影响研究

二氧化铈(CeO₂)具有储量丰富，价格低廉，催化性能优异等特性而得到广泛应用。通过在其晶格中掺杂其他离子制得CeO₂固溶体，可以进一步调控CeO₂的晶格大小，增加晶格缺陷浓度，从而有效提高催化性能。目前研究较多的掺杂离子多为金属阳离子，而对非金属阴离子掺杂的研究尚有待深入探索。本文以CO(NH₂)₂为N源，采用水热法合成不同N掺杂浓度的纳米CeO_2-xN_x固溶体(x=0.00，0.05，0.10，0.15，0.20)，系统对固溶体的微观结构及光谱特征进行表征。X射线衍射(XRD)结果表明，所有掺杂浓度的CeO_2-xN_x固溶体均呈萤石立方单相结构。与纯CeO₂相比，N含量为0.05时样品的晶胞参数显著增大，而随掺杂浓度的进一步增加，晶胞参数又呈现出逐渐减小的趋势。拉曼(Raman)测试表明，N掺杂样品的F_2g振动模式峰向高波数移动，其原因是由于当N3-取代部分O2-后，Ce4+周围出现Ce—N键，Ce—N键长因静电引力变强而缩短，从而引起峰位的移动。通过紫外可见吸收光谱(UV-Vis)分析掺杂所引起样品电子跃迁状态的改变，发现N元素的掺杂使CeO₂在可见光区域具有了吸光性能，CeO_2-xN_x固溶体的能隙明显减小，这是由于N(2p)与O(2p)的电子轨道发生交互作用而形成中间能级，使得电子跃迁所需能量降低，从而引起能隙的红移。荧光光谱(PL)测试表明，发射峰强度随N掺杂浓度的增大而增大，其原因一方面是由于N掺杂会引起晶格缺陷及氧空位比例的提升，发生带间跃迁的几率变大，进而提高发射峰的相对强度；另一方面，N的掺杂在价带O(2p)与导带Ce(4f)间形成中间能带，同样会导致发射峰变强。为表征纳米固溶体的催化特性，分别选取N掺杂量最小的CeO_1.95N_0.05与N掺杂量最高的CeO_1.80N_0.20以及纯CeO₂作为典型催化剂，采用球磨法制备Mg₂Ni/Ni/CeO_2-xN_x复合材料，系统分析了复合材料电极的储氢动力学性能。交流阻抗(EIS)测试发现，催化剂可以有效提高储氢合金的表面电荷转移活性，N掺杂量越高，CeO₂基固溶体的催化活性越强；动电位极化曲线测试表明，掺杂催化剂也能显著提高H原子在合金内部的扩散速率，且CeO_1.95N_0.05较CeO_1.80N_0.20具有更好的催化活性。催化机理主要从催化剂的微观结构及光谱特征进行分析，如前所述，随着N含量的提高，CeO₂固溶体晶格中的氧空位比例增大，晶格畸变程度提高，N的掺杂还使固溶体的电子跃迁能隙降低，从而有利于电子在合金表面的迁移；同时，纳米材料的晶粒尺寸越小，表明晶粒表面缺陷比例越大，说明催化剂的活性增强，因此表现为N掺杂浓度越高，复合材料电极交流阻抗弧半径的越小，即CeO_1.80N_0.20可以更加有效提高复合材料的表面活性；另一方面，若催化剂的晶胞体积增大，可使H原子在穿过材料表面的传输过程中具有更大的空间，由于CeO_1.95N_0.05的晶胞参数大于CeO_1.80N_0.20催化剂，故H原子通过催化剂进入合金内部的传输更加容易。H原子在合金内部的扩散速率与催化剂的晶胞参数或晶胞体积的大小密切相关。     

Towards the preparation of realistic model Ziegler-Natta catalysts: XPS study of the MgCl2/TiCl4 interaction with flat SiO2/Si(1 0 0)

Despite of the wide use of supported Ti based Ziegler-Natta catalysts in the olefin polymerization industry, questions concerning the role of each one of the catalyst components in the polymerization process, have not found a satisfactory answer yet. This is mainly because of the high sensitivity of these systems to oxygen and atmospheric moisture that makes their study in an atomic level rather complicated. Realistic surface science models of the pre-activated SiO₂ supported MgCl₂/TiCl₄ and TiCl₄ Ziegler-Natta catalysts were prepared by spin coating on flat conductive SiO₂/Si(1 0 0) supports under inert atmosphere. This preparation technique resembles the wet chemical impregnation which is the industrial method of the catalyst preparation. XPS analysis showed that the catalyst precursor anchors on the silica surface through bonding of the Ti atoms with surface silanes or siloxanes, while Mg is attached to the Ti through chlorine bridges. Thermal treatment of the catalysts at 723 K leads to total Cl desorption when MgCl₂ is not present while a significant amount of the Ti atoms is reduced to the Ti³⁺ state.     

Bi_xBa_(1-x)TiO_3电子及能带结构的第一性原理研究

采用基于第一性原理的赝势平面波方法,研究了ABO_3钙钛矿复合氧化物BaTiO_3中A位离子被Bi原子取代后对其构型、电子及能带结构的影响.计算结果表明,Bi取代Ba之后会降低BaTiO_3的对称性,空间点群随着取代量的变化而变化,结合能逐渐降低.通过能带结构的计算发现Bi_xBa_(1-x)TiO_3为直接带隙型半导体.Bi的取代可调节Bi_xBa_(1-x)TiO_3的禁带宽度,从x=0.125到x=0.625时,Bi的取代量越大,其带隙越宽,吸收光谱蓝移.x0.625时,禁带宽度又逐渐减小,吸收光谱红移.由态密度图可看出,其价带顶主要是O-2p与Bi-6s态杂化而成,导带底主要由Ti-3d态构成.     

催化前驱体亚硝酰硝酸钌中杂质元素的质谱分析

钌催化前驱体是影响负载型钌催化剂催化性能最重要因素。前驱体中的部分杂质会对催化性能产生抑制作用，尤其是S，P，Cl，As等杂质元素含量过高会降低催化剂的活性，严重时会造成催化剂中毒；因此，必须严格控制催化前驱体中杂质元素的含量。建立了快速准确测定催化前驱体亚硝酰硝酸钌（Ru(NO)(NO₃)₃）中杂质元素的分析方法。Ru(NO)(NO₃)₃经稀硝酸溶解后采用电感耦合等离子体串联质谱（ICP-MS/MS）直接测定其中的8个杂质元素（P，S，Ti，V，Cr，Mn，Fe，As）。为防止Ru(NO)(NO₃)₃溶液水解形成Ru(NO)(NO₃)x(OH)_3-x，采用稀硝酸介质有效维持了样品溶液的稳定性。在MS/MS模式下，通过一级四极杆质量过滤器（Q₁）控制进入碰撞/反应池（CRC）的离子，仅允许与待测元素具有相同质荷比（m/z）的离子进入CRC，从而将来自样品基质和等离子气Ar所形成的干扰离子阻止在CRC外，消除了大量质谱干扰。通过向CRC内通入O₂为反应气，目标离子P+，S+，Ti+，V+，As+与O₂的反应为放热过程（31P++O₂→31P16O++O，ΔH_r=-3.17 eV；32S++O₂→32S16O++O，ΔH_r=-0.34 eV；48Ti++O₂→48Ti16O++O，ΔH_r=-1.63 eV；51V++O₂→51V16O++O，ΔH_r=-0.85 eV；75As++O₂→75As16O++O，ΔH_r=-0.63 eV），能自发反应生成氧化物离子；目标离子Cr+，Mn+与O₂的反应为吸热过程（52Cr++ O₂→52Cr16O++O，ΔH_r=+1.38 eV；55Mn++O₂→55Mn16O++O，ΔH_r=+2.15 eV）。为促进Cr+，Mn+与O₂发生反应，通过调整CRC的工作参数，设置八极杆偏置电压为较大的负电压，使Cr+和Mn+在与O₂反应前被加速，提高Cr+和Mn+的动能，促进了反应的发生，通过吸热反应生成氧化物离子；而P+，S+，Ti+，V+，Cr+，Mn+，As+干扰离子在CRC内不能与O₂发生反应，仍然保持原始的m/z。通过二级四极杆质量过滤器（Q₂）将这些干扰离子阻止在外，仅允许所形成的氧化物离子进入检测器，几乎完全消除了元素P，S，Ti，V，Cr，Mn，As的所有质谱干扰。NH₃因含一对孤对电子而具有高反应活性，能与很多金属离子反应形成团簇离子。通过向CRC内通入NH₃/He为反应气，目标离子Fe+与NH₃发生质量转移反应，在所形成多个团簇离子中，Fe(NH₃)+₂的丰度最高且无干扰，通过NH₃质量转移法消除干扰。结果显示，8个元素在0～500 μg·L-1范围内具有良好的线性关系，线性相关系数≥0.999 8。方法的检出限为0.29～485 ng·L-1，按所建立的方法分析了实际样品中8个杂质元素的含量，各元素的加标回收率为93.2%～107.5%，相对标准偏差（RSD）≤3.9%。方法具有样品处理简单、分析速度快和精密度高的特点，适合催化前驱体亚硝酰硝酸钌中多个杂质元素的准确测定，为制备负载型钌催化剂提供了质量保障。     

Interactions of NH3, coadsorbed with PF3, on Ru(001)

NH₃, coadsorbed with PF₃, on Ru(001) has been studied by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). HREELS shows that the P---F stretching frequency decreases by 60–90 cm⁻¹ in the presence of NH₃. This is explained by the enhancement, in the presence of NH₃, of backdonation of electrons from the metal to the antibonding orbital of the PF₃. The PF₃ bending frequency does not change in the presence of NH₃. This indicates that the σ donation of electrons from PF₃ to the metal substrate is not influenced by coadsorbed NH₃. The intensity of the PF₃ vibrational bands, particularly the PF₃ bending mode, decreases drastically in the presence of NH₃. We interpret this in terms of electric field shielding created by the coadsorbed NH₃ and/or the result of direct interactions between NH₃ and PF₃.     

Tetrakis(diethylamido) titanium (TDEAT) interactions with SiO2 and Cu substrates

X-ray photoelectron spectroscopy (XPS) is used to characterize the chemical interactions of tetrakis(diethylamido) titanium (TDEAT) with SiO₂ and Cu surfaces under ultrahigh vacuum (UHV) conditions. XPS studies show that TDEAT dissociatively chemisorbs on SiO₂ at room temperature or above, resulting in Ti---N bond scission, and Ti---O bond formation. No Ti carbide or Si carbide formation is observed. In the presence of co-adsorbed NH₃, Ti---N bond formation is enhanced and is stable at temperature up to 900 K in UHV. Continuous exposures of TDEAT on SiO₂ at 500 K produce both Ti oxides and nitride formation. The presence of an overpressure of NH₃ enhances Ti nitride formation. In contrast, TDEAT physisorbed on Cu at 120 K and annealed to 500 K results in desorption of Ti-containing species from the surface. Successive exposures of TDEAT on Cu at 500 K yield a Ti-alkyl reaction product. The presence of NH₃ does not significantly alter TDEAT interaction with Cu.     

高纯钼粉中超痕量杂质的质谱分析

建立高纯钼粉中超痕量杂质测定的分析方法。采用电感耦合等离子体串联质谱(ICP-MS/MS)的MS/MS模式,选择H₂为反应气,利用H₂原位质量法测定Si和Ca;选择O₂为反应气,利用O₂原位质量法测定Cd,利用O₂质量转移法测定P,As,Se,Ta,Sn,Sb,Ba和W;选择NH₃/He作为反应气,利用原位质量法测定Na,Mg,Al,K和V,利用质量转移法测定Ti,Cr,Mn,Fe,Co,Ni,Cu,Zn;采用单四极杆(SQ)无气模式测定Pb,Bi,Th和U。与传统的带碰撞/反应池(CRC)电感耦合等离子体质谱(ICP-MS)相比,各元素的背景等效浓度(BEC)和检出限更低,消除质谱干扰更加彻底。在优化的工作条件下,28种元素的线性相关系数(R2)≥0.999 7,线性关系良好,检出限为0.04～50.1 ng·L-1,加标回收率为92.2%～107.4%,相对标准偏差(RSD)≤4.3%,表明所建立的分析方法具有极好的准确性和精密度。实际样品的分析结果显示,方法可用于纯度为5N(≥99.999%)高纯钼粉中28个杂质元素的测定。     

Insights into the adsorption of water and oxygen on the cubic CsPbBr3 surfaces: A first-principles study

The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear. In this paper, water and oxygen molecule adsorptions on the all-inorganic perovskite (CsPbBr₃) surface are studied by density-functional theory calculations. In terms of the adsorption energy, the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr₃ surface. The water molecules can be adsorbed on both the CsBr- and PbBr-terminated surfaces, but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference. While the adsorbed water molecules only contribute deep states, the oxygen molecules introduce interfacial states inside the bandgap of the perovskite, which would significantly impact the chemical and transport properties of the perovskite. Therefore, special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr₃-based devices.     

ScF3，NaScF4，(NH4)2NaScF6的可控合成与上转换发光性能的研究

钪基氟化物化学性质稳定、声子能量低、无辐射弛豫概率较低,是一种新型高效的基质材料,并且Sc3+半径较小,能与多种氨羧络合剂形成稳定的螯合物,因而具有更加奇特的物理和化学性质,近年来,成为许多科学家研究的热点。以聚乙烯二胺(PEI)作为表面活性剂,采用水热法在反应温度为200 ℃时成功制备了ScF₃∶Yb3+/Er3+,NaScF₄∶Yb3+/Er3+,(NH₄)₂NaScF₆∶Yb3+/Er3+纳米上转换发光材料。通过X射线衍射仪(XRD)、透射电镜(TEM)、扫描电镜(SEM)和荧光光谱仪对所制备样品的晶相、形貌和发光特性进行了研究,结果显示：通过改变反应物NH₄F和Ln3+的比例(NH₄F/Ln3+=1∶1,2∶1,2.5∶1,3∶1,4∶1,6∶1,10∶1,20∶1,30∶1,40∶1,50∶1)实现了对样品产物、晶相、形貌的控制。当NH₄F/Ln3+为2.5∶1时,生成了纯立方相的ScF₃;在NH₄F/Ln3+为4∶1时,生成了六角相的NaScF₄;在NH₄F/Ln3+为40∶1时,生成了一种纯立方相的新型基质材料(NH₄)₂NaScF₆,样品结晶度高,形貌均一,有正方形片状和足球状多面体;在980 nm红外激光的激发下,不同NH₄F/Ln3+比例生成的样品发光呈现桔黄→桔红→绿→黄绿等多种颜色的变化。实验表明仅改变NH₄F一种原料的用量,就可以生成ScF₃∶Yb3+/Er3+,NaScF₄∶Yb3+/Er3+和(NH₄)₂NaScF₆∶Yb3+/Er3+ 三种不同的产物,说明NH₄F的用量对产物的生成有决定性的作用,对晶相的转换、颜色的调控亦有重要影响。     

The preparation and properties of highly conductive nonstoichiometric oxide catalysts

Inter-oxide compounds of rare earth and transition metal oxides can be made highly nonstoichiometric by the partial substitution of divalent ions, such as strontium, for the rare earth element. These compounds become highly conductive when suitably treated in oxygen at high temperatures, and have been found to function as efficient oxidation catalysts at low temperatures between 100–300°C. The thermodynamics, transport properties and catalytic behavior for CO and CH₄ oxidation of some systems having the perovskite or the K₂NiF₄ structure are discussed, e.g. La_1−xSr_xMO_3−δ(M=Cr,Mn,Fe,Co,Y) and La_2−xSr_xCuO_4−δ. The catalytic behavior is similar for the Cr,Mn,Fe and Co perovskites, but the solid electrolyte La_0.8Sr_0.2YO_2.9 has no effect in CO oxidation but the greatest activity for CH₄ oxidation.     

Nitridation of thin SiO2 films in N2 and NH3 plasmas

A low-temperature (700°C) plasma-enhanced nitridation process which improves the dielectric breakdown of thin silicon dioxide (SiO₂) layers is presented. It uses a new, production compatible, parallel plate plasma reactor working at low RF frequencies. Nitrided oxides produce less charge trapping under high field stress, higher breakdown charge and a tighter distribution of breakdown fields than pure SiO₂. More nitrogen is incorporated in films treated in a NH₃ plasma than in a N₂ plasma. However, the latter present better electrical properties.     

有机无机杂化固态太阳能电池的研究进展

近年来, 由于钙钛矿材料优良的光学吸收和电荷传导特性, 有机无机杂化固态太阳能电池取得了突破性的进展. 自2009年首次报道了光电转换效率为3.8%的钙钛矿太阳能电池以来, 该类电池的效率不断突破. 基于介孔薄膜的电池已取得了超过16.7%的认证光电转换效率, 基于平板异质结结构电池光电转换效率达到19.3%, 已接近传统硅基太阳能电池的光电转换效率. 本文将介绍有机无机杂化钙钛矿作为光电材料的光学物理结构特性, 以及在固态太阳能电池中的应用. 基于固态钙钛矿太阳能电池结构上的差异, 分别介绍其在多孔结构、平板异质结结构、柔性结构以及无空穴传导材料结构电池工作特性和各自优势, 以及影响电池特性的主要影响因素, 特别是钙钛矿成膜控制等. 并阐述对钙钛矿电池的理解和进一步提高固态钙钛矿电池光电转换效率需要关注的重点以及展望.     

铜纳米阵列高效电解水产氧催化剂的制备

本文报道了一种利用简单的两步牺牲模板法,在泡沫铜基底表面完成了三维氧化铜纳米晶阵列的生长. 氧化铜纳米晶阵列具有良好的导电性,稳定性,在碱性溶液中有着优秀的电解水产氧催化性能. 氧化铜纳米晶阵列催化水的电化学氧化只需400 mV的过电势即可达到100 mA/cm²的电流密度,与其它铜基电解水产氧催化剂以及贵金属IrO₂相比都有着明显的优势. 氧化铜纳米晶阵列在270 mA/cm²左右的工作电流下连续工作10 h依然可以保持良好的稳定性,是相同的工作电压下IrO₂工作电流的10倍(约25 mA/cm²).     

Possible ferrimagnetism and ferroelectricity of half-substituted rare-earth titanate: A first-principles study on Y0.5La0.5TiO3

Titanates with the perovskite structure, including ferroelectrics (e.g., BaTiO₃) and ferromagnetic ones (e.g., YTiO₃), are important functional materials. Recent theoretical studies predicted multiferroic states in strained EuTiO₃ and titanate superlattices, the former of which has already been experimental confirmed. Here, a first-principles calculation is performed to investigate the structural, magnetic, and electronic properties of Y half-substituted LaTiO₃. Our results reveal that the magnetism of Y_0.5La_0.5TiO₃ sensitively depends on its structural details because of the inherent phase competition. The lowest energy state is the ferromagnetic state, resulting in 0.25 μB/Ti. Furthermore, some configurations of Y_0.5La_0.5TiO₃ exhibit hybrid improper polarizations, which can be significantly affected by magnetism, resulting in the multiferroic properties. Because of the quenching disorder of substitution, the real Y_0.5La_0.5TiO₃ material with random A-site ions may exhibit interesting relaxor behaviors.