Improvement effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)on hydrogen storage performance of MgH_(2)

The hydrogen absorption/desorption kinetic properties of MgH_(2)can be effectively enhanced by doping specific catalysts.In this work,MOFs-derived NiCu@C nanoparticles(~15 nm)with regular core-shell structure were successfully prepared and introduced into MgH_(2)(denoted as MgH_(2)-NiCu@C).The onset and peak temperatures of hydrogen desorption of MgH_(2)-11 wt.%NiCu@C are 175.0℃and282.2℃,respectively.The apparent activation energy of dehydrogenated reaction is 77.2±4.5 kJ/mol for MgH_(2)-11 wt.%NiCu@C,which is lower than half of that of the as-milled MgH_(2).Moreover,MgH_(2)-11 wt.%NiCu@C displays great cyclic stability.The strengthening"hydrogen pumping"effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)is proposed to explain the remarkable improvement in hydrogen absorption/desorption kinetic properties of MgH_(2).This work offers a novel perspective for the design of bimetallic nanoparticles and beyond for application in hydrogen storage and other energy related fields.

Magnesium nickel hydride monocrystalline nanoparticles for reversible hydrogen storage

Although Mg-based hydrides are extensively considered as a prospective material for solid-state hydrogen storage and clean energy carriers,their high operating temperature and slow kinetics are the main challenges for practical application.Here,a Mg-Ni based hydride,Mg_(2)NiH_(4) nanoparticles(~100 nm),with dual modification strategies of nanosizing and alloying is successfully prepared via a gas-solid preparation process.It is demonstrated that Mg_(2)NiH_(4) nanoparticles form a unique chain-like structure by oriented stacking and exhibit impressive hydrogen storage performance:it starts to release H2 at~170℃ and completes below 230℃ with a saturated capacity of 3.32 wt%and desorbs 3.14 wt% H_(2) within 1800 s at 200℃.The systematic characterizations of Mg_(2)NiH_(4) nanoparticles at different states reveal the dehydrogenation behavior and demonstrate the excellent structural and hydrogen storage stabilities during the de/hydrogenated process.This research is believed to provide new insights for optimizing the kinetic performance of metal hydrides and novel perspectives for designing highly active and stable hydrogen storage alloys.

Facet-dependent catalytic activity of two-dimensional Ti_(3)C_(2)T_(x) MXene on hydrogen storage performance of MgH_(2)

Two-dimensional Ti_(3)C_(2)T_(x) MXenes exposing different active facets are introduced into MgH_(2), and their catalytic effects are systematically investigated in depth through experimental and theoretical approaches. Excluding factors such as interlayer space, surface functional groups and experimental contingency, the exposed facets is considered to be the dominant factor for catalytic activity of Ti_(3)C_(2)T_(x) towards MgH_(2).More exposed edge facets of Ti_(3)C_(2)T_(x) displays higher catalytic activity than that with more exposed basal facets, which also leads to different rate-controlling steps of MgH_(2) in the de/hydrogenation process. The low work function, strong hydrogen affinity and high content of in situ metallic Ti for the edge facet contribute the high catalytic activity. This work will give insights into the structural design of two-dimensional Ti_(3)C_(2)T_(x) MXene used for enhancing the catalytic activity in various fields.

Suppressed oxygen extraction and degradation of LiNixMnyCo2O2 cathodes at high charge cut-off voltages

The capacity degradation mechanism in lithium nickel-manganese-cobalt oxide （NMC） cathodes （LiNi1/3Mn1/3Co1/3O2 （NMC333） and LiNi0.4Mn0.4Co0.2O2 （NMC442）） during high-voltage （cut-off of 4.8 V） operation has been investigated. In contrast to NMC442, NMC333 exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure, as well as interfacial degradation during high-voltage cycling, leading to a rapid increase of the electrode resistance and fast capacity decline. The fundamental reason behind the poor structural and interracial stability of NMC333 was found to be correlated to its high Co content and the significant overlap between the Co3＋/4＋ t2g and O2- 2p bands, resulting in oxygen removal and consequent structural changes at high voltages. In addition, oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species, which then attack the electrode surface and form highly resistive LiF. These findings highlight that both the structural and interfacial stability should be taken into account when tailoring cathode materials for high voltage battery systems.

Genomic analysis,trajectory tracking,and field surveys reveal sources and long-distance dispersal routes of wheat stripe rust pathogen in China

Identifying sources of phytopathogen inoculum and determining their contributions to disease outbreaks are essential for predicting disease development and establishing control strategies.Puccinia striiformis f.sp.tritici(Pst),the causal agent of wheat stripe rust,is an airborne fungal pathogen with rapid virulence variation that threatens wheat production through its long-distance migration.Because of wide variation in geographic features,climatic conditions,and wheat production systems,Pst sources and related dispersal routes in China are largely unclear.In the present study,we performed genomic analyses of 154 Pst isolates from all major wheat-growing regions in China to determine Pst population structure and diversity.Through trajectory tracking,historical migration studies,genetic introgression analyses,and field surveys,we investigated Pst sources and their contributions to wheat stripe rust epidemics.We identified Longnan,the Himalayan region,and the Guizhou Plateau,which contain the highest population genetic diversities,as the Pst sources in China.Pst from Longnan disseminates mainly to eastern Liupan Mountain,the Sichuan Basin,and eastern Qinghai;that from the Himalayan region spreads mainly to the Sichuan Basin and eastern Qinghai;and that from the Guizhou Plateau migrates mainly to the Sichuan Basin and the Central Plain.These findings improve our current understanding of wheat stripe rust epidemics in China and emphasize the need for managing stripe rust on a national scale.

Air-stable magnesium nickel hydride with autocatalytic and self-protective effect for reversible hydrogen storage

Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In this work,a novel method,namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure,was proposed to synthesize air stable and autocatalytic magnesium nickel hydride(Mg2NiH4),which shows excellent hydrogen absorption/desorption kinetics,capacity retention and oxidation resistance.The short-term-milled Mg2NiH4 can desorb 2.97 wt.%hydrogen within 500 s at 230℃.Even after exposure under air atmosphere for 67 days,it can still desorb 2.88 wt.%hydrogen within 500 s at 230℃.The experimental and theoretical results both indicated that the surface of as-milled Mg2NiH4 was easy to be oxidized under air atmosphere.However,the in-situ formed Ni during air exposure of Mg2NiH4 improved the hydrogen desorption kinetics,and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning,which we called autocatalytic and self-protective effect.Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg2NiH4.Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.

Assisting Ni catalysis by CeO_(2) with oxygen vacancy to optimize the hydrogen storage properties of MgH_(2)

Although MgH_(2) has been widely regarded as a promising material for solid-state hydrogen storage,its high operating temperature and slow kinetics pose a major bottleneck to its practical application.Here,a nanocomposite catalyst with interfacial coupling and oxygen defects,Ni/CeO_(2),is fabricated to promote H_(2) desorption and absorption properties of MgH_(2).The interface of Ni/CeO_(2) contributes to both strong mechanical coupling towards stabilizing partial Ni and electronic coupling towards inducing a high con-centration of oxygen vacancies in CeO_(2).Theoretical calculations evidence that CeO_(2) with oxygen vacancy assist Ni in weakening the energy of Mg-H bond as well as enhancing the adsorption energy of Ni upon hydrogen atoms,and the extent of this assistance surprisingly increases with increasing oxygen vacancies concentration.As a result,an impressive performance is achieved by MgH_(2)-5 wt.%Ni/CeO_(2) with onset desorption temperature of only 165°C,and it absorbs approximately 80%hydrogen in just 800 s at 125°C.The generation mechanism of intermediate active species concerning Ni/CeO_(2) in different states has been analyzed for the first time,and the relationship between interfacial coupling and phase evolution has been elucidated.Therefore,a mechanism of the catalysis-assisting effect regarding oxygen defects is proposed.It is believed that this work provides a unique perspective on the mechanism of interfacial coupling and the generation of defects in composite catalysts.

Reviewing the impact of halides on electrochemical CO_(2) reduction

Electrochemical CO_(2) reduction reaction(CO_(2)RR)is a promising technology for mitigating global warming and storing renewable energy.Designing low-cost and efficient electrocatalysts with high selectivity is a priority to facilitate CO_(2) conversion.Halide ion(F^(-),Cl^(-),Br^(-),I^(-))modified electrocatalysts is a potential strategy to promote CO_(2) reduction and suppress the competitive hydrogen evolution reaction(HER).Therefore,a comprehensive review of the role and mechanism of halide ions in the CO_(2)RR process can help better guide the future design of efficient electrocatalysts.In this review,we first discuss the role of halide ions on the structure and morphology of electrocatalysts.Secondly,the relationship between the halide ions and the valence states of the active sites on the catalyst surface is further elaborated on.Thirdly,the mechanisms of halide in enhancing CO_(2) conversion efficiency are also summarized,including the involvement of halide ions in electron transfer and their influence on the reaction pathway.Finally,we conclude with a summary and future outlook.