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Air-stability is one of the most important considerations for the practical application of electrode materials in energy-harvesting/storage devices, ranging from solar cells to rechargeable batteries. The promising P2-layered sodium transition metal oxides (P2-Na x TmO 2 ) often suffer from structural/chemical transformations when contacted with moist air. However, these elaborate transitions and the evaluation rules towards air-stable P2-Na x TmO 2 have not yet been clearly elucidated. Herein, taking P2-Na 0.67 MnO 2 and P2-Na 0.67 Ni 0.33 Mn 0.67 O 2 as key examples, we unveil the comprehensive structural/chemical degradation mechanisms of P2-Na x TmO 2 in different ambient atmospheres by using various microscopic/spectroscopic characterizations and first-principle calculations. The extent of bulk structural/chemical transformation of P2-Na x TmO 2 is determined by the amount of extracted Na + , which is mainly compensated by Na + /H + exchange. By expanding our study to a series of Mn-based oxides, we reveal that the air-stability of P2-Na x TmO 2 is highly related to their oxidation features in the first charge process and further propose a practical evaluating rule associated with redox couples for air-stable Na x TmO 2 cathodes.

Renewable energy-driven methanol synthesis from CO2 and green hydrogen is a viable and key process in both the “methanol economy” and “liquid sunshine” visions. Recently, In2O3-based catalysts have shown great promise in overcoming the disadvantages of traditional Cu-based catalysts. Here, we report a successful case of theory-guided rational design of a much higher performance In2O3 nanocatalyst. Density functional theory calculations of CO2 hydrogenation pathways over stable facets of cubic and hexagonal In2O3 predict the hexagonal In2O3(104) surface to have far superior catalytic performance. This promotes the synthesis and evaluation of In2O3 in pure phases with different morphologies. Confirming our theoretical prediction, a novel hexagonal In2O3 nanomaterial with high proportion of the exposed {104} surface exhibits the highest activity and methanol selectivity with high catalytic stability. The synergy between theory and experiment proves highly effective in the rational design and experimental realization of oxide catalysts for industry-relevant reactions.

Sodium-ion batteries are promising alternatives to lithium-ion batteries for large-scale applications. However, the low capacity and poor rate capability of existing anodes for sodium-ion batteries are bottlenecks for future developments. Here, we report a high performance nanostructured anode material for sodium-ion batteries that is fabricated by high energy ball milling to form black phosphorus/Ketjenblack-multiwalled carbon nanotubes (BPC) composite. With this strategy, the BPC composite with a high phosphorus content (70 wt %) could deliver a very high initial Coulombic efficiency (>90%) and high specific capacity with excellent cyclability at high rate of charge/discharge (∼1700 mAh g(-1) after 100 cycles at 1.3 A g(-1) based on the mass of P). In situ electrochemical impedance spectroscopy, synchrotron high energy X-ray diffraction, ex situ small/wide-angle X-ray scattering, high resolution transmission electronic microscopy, and nuclear magnetic resonance were further used to unravel its superior sodium storage performance. The scientific findings gained in this work are expected to serve as a guide for future design on high performance anode material for sodium-ion batteries.

Direct synthesis of aromatics from syngas is a great challenge because of severe operating conditions and low yield of aromatics. Making this process more competitive than the MTA (methanol to aromatics) process will require high energy efficiency and low CO 2 emission. A combination of Na-Zn-Fe 5 C 2 and hierarchical HZSM-5 with uniform mesopores dramatically changed the product distribution of Fischer-Tropsch synthesis, leading to 51% aromatic selectivity under the stable stage with CO conversion >85%. C 12+ heavy hydrocarbons almost disappeared, and the catalyst showed good stability. The hierarchical zeolitic structure and Brønsted acidity of HZSM-5 could be precisely tuned by controlling the alkali treatment conditions and the degree of ion exchange. The appropriate density and strength of the Brønsted acid sites and the hierarchical pore structure of HZSM-5 endowed the catalyst with an unprecedented aromatic yield. This work shows a broad area for development for syngas conversion.Recently, a high-performance catalyst, Na-Zn-Fe 5 C 2 (termed as FeZnNa), was developed by the co-precipitation method (Figures S1-S3). 22 The molar weight ratio of

Due to their high specific capacities beyond 250 mAh g-1, lithium-rich oxides have been considered as promising cathodes for the next generation power batteries, bridging the capacity gap between traditional...

The full potential energy surface of the catalytic conversion of furfural to 2-methylfuran on the Cu(111) surface has been systematically computed on the basis of density functional theory, including dispersion and zero-point energy corrections. For furfuryl alcohol formation, the more favorable step is the first H addition to the carbon atom of the CO group, forming an alkoxyl intermediate (F-CHO +H → F-CH2O); the second H atom addition, leading to furfuryl alcohol formation (F-CH2O + H → F-CH2OH), is the rate-determining step. For 2-methylfuran formation from furfuryl alcohol dissociation into surface alkyl (F-CH2) and OH groups, H2O formation is the rate-determining step (OH + H → H2O). Our results explain perfectly the experimentally observed selective formation of furfuryl alcohol and the equilibrium of furfural/furfuryl alcohol conversion under hydrogen-rich conditions as well as the effect of H2O suppressing furfural conversion. In addition, it is found that dispersion correction (PBE-D3) overestimates the adsorption energies of furfural, furfuryl alcohol, and 2-methylfuran considerably, whereas those of H2 and H2O can be reproduced nearly quantitatively. Our results provide insights into Cu-catalyzed furfural selective conversion and broaden our fundamental understanding into deoxygenation reactions of oxygenates involved in the refining of biomass-derived oils.

The influence of different iron carbides on the activity and selectivity of iron-based Fischer−Tropsch catalysts has been studied. Different iron carbide phases are obtained by the pretreatment of a binary Fe/SiO 2 model catalyst (prepared by coprecipitation method) to different gas atmospheres (syngas, CO, or H 2 ). The phase structures, compositions, and particle sizes of the catalysts are characterized systematically by XRD, XAFS, MES, and TEM. It is found that in the syngas-treated catalyst only χ-Fe 5 C 2 carbide is formed. In the CO-treated catalyst, Fe 7 C 3 and χ-Fe 5 C 2 with a bimodal particle size distribution are formed, while the H 2 -treated catalyst exhibits the bimodal size distributed ε-Fe 2 C and χ-Fe 5 C 2 after a Fischer−Tropsch synthesis (FTS) reaction. The intrinsic FTS activity is calculated and assigned to each corresponding iron carbide based on the phase composition and the particle size. It is identified that Fe 7 C 3 has the highest intrinsic activity (TOF = 4.59 × 10 −2 s −1 ) among the three candidate carbides (ε-Fe 2 C, Fe 7 C 3 , and χ-Fe 5 C 2 ) in typical medium-temperature Fischer−Tropsch (MTFT) conditions (260−300 °C, 2−3 MPa, and H 2 /CO = 2). Moreover, FTS over ε-Fe 2 C leads to the lowest methane selectivity.