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Lattice, Magnetism, and Transport in SrRuO3 Co-doped with La and Mn

Fu Shuai,Tan Yiyu,Sun Xiaofan,Tang Zheng,Jiao Shulin,Cai H. L.,Zhang F. M.,Zhang A. M.,Wu X. S.

Here, equal numbers of La and Mn ions are successfully introduced simultaneously in SrRuO3. With increasing La/Mn doping, all compositions crystallize in Pnma with the lattice constant, together with the RuO 6 octahedral distortion, decreases. Ferromagnetism-to-spin glass magnetic behavior is observed at x  ≥ 0.23. A metal–insulator transition (MIT) occurs at lower temperatures, resulting from the disordering of the metal mixture in the lattice. The retraction of the RuO 6 octahedron increases the overlap of the Ru t 2g –O 2p orbitals and broadens the Ru 4d bandwidth, leading to weaker electron–electron interactions, which may decrease the electronic and thermal conductivity.

Mn-doped perovskite quantum dots with thermal stability synthesized at room temperature

Wenzhi Wang,Liwei Wang,Shuo Song,Xinxin Guo,Hongyu Liu,Guangqiang Liu

All inorganic perovskite quantum dots (PQDs) have been studied extensively because of their excellent photoelectric properties. However, its poor stability and lead toxicity limit its practical application. At the same time, the complex synthesis conditions of the hot injection method also limited the preparation of large quantities. Here, we have successfully synthesized Mn-doped CsPb(Cl/Br) 3 PQDs with excellent thermal stability at room temperature by a simple supersaturation crystallization method. The synthesized Mn-doped CsPb(Cl/Br) 3 PQDs has good homogeneity and crystallinity. Meanwhile, Mn-doped CsPb(Cl/Br) 3 PQDs maintains the same crystal structure as CsPb(Cl/Br) 3 PQDs. Importantly, it was found that the activation energy of CsPb(Cl/Br) 3 PQDs after manganese doping increased from 65.1 meV to 222.8 meV through the high and low temperature PL test of 80 K–500 K. The crystal structure of CsPb(Cl/Br) 3 PQDs is more stable due to the introduction of manganese ion, and the thermal stability is significantly improved. In this study, manganese doped CsPb(Cl/Br) 3 PQDs with good crystallinity and thermal stability was rapidly synthesized by a simple supersaturation crystallization method at room temperature, which opened up a new way to improve the stability of PQDs and explore other non-toxic metal elements to replace Pb 2+ .

Reproducible mechanical-to-optical energy conversion in Mn (II) doped sphalerite ZnS

Ronghua Ma,Xiaoyan Wei,Chunfeng Wang,Shaohui Mao,Bing Chen,Yonghong Shao,Yu Fu,Keyu Yan,Dengfeng Peng

Mechanoluminescenece (ML) is a dynamic luminescence phenomenon of materials under various mechanical stimulation. Impurity doped ZnS shows high ML repeatability without any needs for extra excitation sources, thus making it very promising in applications like stress sensing and battery-free new light source . Lots of progress has been made in the last decades, however, the reproducible ML (RML) mechanism is still unclear to explain some basic phenomena like how the electron is excited to conduction band when undergoing mechanical actions or how the excitation energy is transferred to the dopants so efficiently. Based on comparative study of photoluminescence (PL) and ML in Mn 2+ doped ZnS prepared via melt-salt method, the RML energy routes in sphalerite ZnS: Mn 2+ is proposed herein, and further, a general mechanism is supposed which could apply to other RML systems. The excitation of RML is possibly generated by electron transfer during bond rebuilding in plastic deformation while the highly efficient energy transfer is realized through hole and electron capture by the dopant. According to this mechanism, we provide some prospects for further optimization of RML performance as well as discovery of new RML materials.

Investigating the luminescence mechanism of Mn-doped CsPb(Br/Cl)3 nanocrystals

Jinjin Ma,Qianting Yao,John A. McLeod,Lo-Yueh Chang,Chih-Wen Pao,Jiatang Chen,Tsun-Kong Sham,Lijia Liu

Inorganic lead halide perovskite CsPbX3 (X = Cl, Br, or I) nanocrystals are promising candidate materials for light-emitting devices and optoelectronics. Mn-Doped CsPbX3 is of particular interest, as the Mn-doping introduces an additional emission band, making this material a promising white-light emitter. In this study, Mn-doped CsPb(Br/Cl)3 nanocrystals are prepared at room-temperature and ambient pressure. The chemical environment of Mn, and the luminescence of these nanocrystals are analyzed in detail using X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL). Although the introduction of Mn does not alter the long-range order of the CsPbX3 crystal, it leads to a local lattice contraction with the bond length of Mn–X much shorter than Pb–X. We also find excitation energy-dependence in both the intensity and wavelength of the perovskite excitonic emission band, while only in intensity of the Mn emission band. Detailed fitting of the XEOL reveals that the perovskite emission band is dual-channel, and it is the excitation energy-dependent intensity variation of these two channels that drives the observed red-shift of the combined emission band. Our findings also confirm that the Mn emission band is driven by exciton-Mn energy transfer and clarify the Mn chemical environment and the luminescence mechanism in Mn-doped CsPb(Br/Cl)3 nanocrystals.

Demonstration of electrocatalytic oxygen evolution activity of V4AlC3 (Mn+1AXnPhase) bulk powders

Haiyun Tong,Shuai Lin,Hanlu Zhang,Xin Wang,Yanan Huang,Bangchuan Zhao,Xuebin Zhu,Yuping Sun

The present work reports oxygen evolution reaction (OER) activity in metallic V 4 AlC 3 bulk powders prepared by solid-state reactions for the first time. An ultralow overpotential of 253 mV at the current density of 10 mA cm −2 and an excellent stability are observed, demonstrating that V 4 AlC 3 bulk powder can be used as an excellent new type of OER catalyst with low-cost for mass production.

High Catalytic Performance of Mn-Doped Ce-Zr Catalysts for Chlorobenzene Elimination

Lei Zhu,Xi Li,Zhiying Liu,Lin Yao,Peng Yu,Ping Wei,Yanhua Xu,Xingmao Jiang

Mn-Ce-Zr-O catalysts doped with varying Mn content were prepared and assessed for the catalytic combustion of chlorobenzene (CB). Nanosized MCZ-0.67 catalyst with amorphous phase exhibited a high and stable catalytic activity among the studied catalysts, achieving 90% CB conversion at 226 °C and withstanding stability tests, including time-based stability and the successive influence of various operating conditions. Meanwhile, the MCZ-0.67 catalyst used showed good recyclability by calcination in air. Characterization results suggested that Mn doping played a dominant role in improving the catalytic performance, resulting in larger surface area, better redox properties and greater amounts of surface active oxygen. In addition, the introduction of Zr was also indispensable for maintaining the good catalytic performance of catalysts. Finally, trace amounts of polychlorinated by-products during CB oxidation were monitored and the oxidation process was discussed.Keywords:MnOx-CeO2-ZrO2;catalytic combustion;chlorobenzene;active oxygen;product analysis

Silver enhanced oxidative coupling of methane over the Mn–Na2WO4/SiO2 catalyst

Yilin Zhao,Fangwei Liu,Jingbo Hu,Yang Yang,Jianzhou Wu,Shihui Zou,Jie Fan

The Mn–Na2WO4/SiO2 catalyst for oxidative coupling of methane (OCM) is highly appealing and promising but its high light-off temperature (>800 °C) hinders its industrial application. Engineering catalysts for efficient catalytic performance is attractive yet challenging. In this study, we demonstrate that the incorporation of small amounts of silver into the Mn–Na2WO4/SiO2 catalyst significantly improves its performance, achieving a C2 yield of up to 20% at 750 °C. Characterization results indicate that silver facilitates O2 activation and promotes C–H bond activation, thereby further enhancing CH4 conversion. The findings offer valuable insights into advancing the design concept of high-performance OCM catalysts.

Mn–CoP/NC bifunctional catalysts with nanocube structures for alkaline water decomposition

Yuying Li,Shengxiong Liao,Yiming Gao,Dai Dang,Yuying Zheng,Fashen Chen

Developing highly efficient non-precious metal bifunctional catalysts remains a critical challenge in electrolytic water splitting research. In this study, we prepared Mn-doped CoP coupled with nitrogen-doped carbon nanocube (Mn–CoP/NC) catalysts using an in situ growth, low temperature oxidation, and phosphatization strategy. Due to the excellent activity of the cobalt species and the effective protection provided by the carbon shell to the metal core, these Mn–CoP/NC catalysts exhibited outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances. At a current density of 10 mA cm2, the overpotentials were as low as 90 mV for the HER and 272 mV for the OER. Moreover, the Mn–CoP/NC‖Mn–CoP/NC cell achieved a current density of 10 mA cm−2 at just 1.66 V and remained highly stable after 36 hours of continuous operation. This study offers a new strategy for designing efficient bifunctional catalysts for overall water splitting.

Enhanced Oxidation of Xylene Using Plasma Activation of an Mn/Al2O3 Catalyst

Zuliang Wu,Weili Zhou,Zhoubin Zhu,Xiaodong Hao,Xuming Zhang

Triple-function Mn regulation of NiFe (oxy)hydroxide for oxygen evolution reaction

Hui Wan,Meng-Yuan Xie,Bo Li,Jian-Hang Nie,Tao Huang,Lei Li,Jing-Hui Shi,Ming-Hua Xian,Jia-Rong Huang,Wangyu Hu,Gui-Fang Huang,Fei Gao,Wei-Qing Huang

Transition metal (oxy)hydroxides are potential oxygen evolution reaction (OER) electrocatalysts; however, simultaneously modulating multiple factors to enhance their performance is a grand challenge. Here, we report an incorporating heteroatom strategy via one-step hydrothermal approach to adjust more than one factor of Mn-doped NiFe (oxy)hydroxide (Mn-NiFeOOH/LDH) heterojunction . Mn doping regulates heterojunction morphology (reducing nanoparticles and becoming thinner and denser nanosheets), Ni/Fe ratio and valence states (Ni 2+ , Ni 3+ , and Ni 3+Δ ) of Ni ions. The former could effectively increase surface active sites, and the latter two reduce the content of Fe in the Mn x -NiFeOOH/LDH heterojunction, enabling more Ni 2+ convert to Ni 3+/3+Δ that have higher intrinsic OER activity. As a result, the first-rank Mn-NiFeOOH/LDH with ultra-low overpotential of 185 mV@20 mA cm −2 and 296 mV@500 mA cm −2 , and the improved OER performance are outdo to those of commercial RuO 2 catalyst for OER. Moreover, the Mn-NiFeOOH/LDH affords the earliest initial potential (1.392 V vs. RHE), corresponds to a recorded low overpotential (162 mV). Based on the density functional theory (DFT), Mn dopants can alter intermediate adsorption energy and effectively decrease *OOH’s energy barrier. This research exhibits a feasible strategy to design low cost electrocatalysts and provide new possibilities for future industrialization.

Zero Voltage-Degradation of Li2MnO3 with Ultrathin Amorphous Li─Mn─O Coating

Shiqi Liu,Jie Wan,Boya Wang,Chenghan Li,Yulong Wang,Lin Wang,Haipeng Wu,Nian Zhang,Xu Zhang,Haijun Yu

Manganese-based lithium-rich layered oxides (Mn-LLOs) are promising candidate cathode materials for lithium-ion batteries, however, the severe voltage decay during cycling is the most concern for their practical applications. Herein, an Mn-based composite nanostructure constructed Li 2 MnO 3 (LMO@Li 2 MnO 3 ) is developed via an ultrathin amorphous functional oxide Li x MnO y coating at the grain surface. Due to the thin and universal LMO amorphous surface layer etched from the lithiation process by the high-concentration alkaline solution, the structural and interfacial stability of Li 2 MnO 3 are enhanced apparently, showing the significantly improved voltage maintenance, cycle stability, and energy density. In particular, the LMO@Li 2 MnO 3 cathode exhibits zero voltage decay over 200 cycles. Combining with ex situ spectroscopic and microscopic techniques, the Mn 2+/4+ coexisted behavior of the amorphous LMO is revealed, which enables the stable electrochemistry of Li 2 MnO 3 . This work provides new possible routes for suppressing the voltage decay of Mn-LLOs by modifying with the composite functional unit construction.

Enhancing Mn Emission of CsPbCl3 Perovskite Nanocrystals via Incorporation of Rubidium Ions

Jian Yang,Xi Yuan,Lin Fan,Yuzhu Zheng,Fanshu Ma,Haibo Li,Jialong Zhao,Huilian Liu

Mn doped cesium lead halide perovskite nanocrystals (NCs) have potential application for white light emitting diodes. However, the emission of doped NCs is limited to trap-mediated energy transfer. The Mn doped CsPbCl 3 NCs with corporation of rubidium (Rb + ) ions (Mn:Cs 1-x Rb x PbCl 3 NCs, x = 0, 0.1, 0.2, 0.3, and 0.4) were synthesized. The effect of the optical and structural properties of Mn:Cs 1-x Rb x PbCl 3 NCs were studied by steady-state and time-resolved photoluminescence spectroscopy. The photoluminescence quantum yields and lifetimes of Mn doped CsPbCl 3 NCs with different Rb + contents were obtained. It was found that the Mn doped CsPbCl 3 NCs with Rb + content of 0.1 exhibited the highest Mn 2+ emission quantum yield up to 63.18%. Interestingly, the temperature-dependent PL spectra demonstrated the enhanced Mn 2+ emission of Mn doped CsPbCl 3 NCs at low temperature of 80 K. The experimental result indicated the Mn 2+ emission of Mn doped CsPbCl 3 NCs was enhanced by incorporating Rb + ions.