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Electrocatalysis represents a promising method to generate renewable fuels and chemical feedstock from the carbon dioxide reduction reaction (CO 2 RR). However, traditional electrocatalysts based on transition metals are not efficient enough because of the high overpotential and slow turnover. MXenes, a family of two-dimensional metal carbides and nitrides, have been predicted to be effective in catalyzing CO 2 RR, but a systematic investigation into their catalytic performance is lacking, especially on hydroxyl (−OH)-terminated MXenes relevant in aqueous reaction conditions. In this work, we utilized first-principles simulations to systematically screen and explore the properties of MXenes in catalyzing CO 2 RR to CH 4 from both aspects of thermodynamics and kinetics. Sc 2 C(OH) 2 was found to be the most promising catalyst with the least negative limiting potential of −0.53 V vs RHE. This was achieved through an alternative reaction pathway, where the adsorbed species are stabilized by capturing H atoms from the MXene's OH termination group. New scaling relations, based on the shared H interaction between intermediates and MXenes, were established. Bader charge analyses reveal that catalysts with less electron migration in the *(H)COOH → *CO elementary step exhibit better CO 2 RR performance. This study provides new insights regarding the effect of surface functionalization on the catalytic performance of MXenes to guide future materials design.

Electrochemical carbon dioxide reduction reaction (CO2RR) represents a promising way to generate fuels and chemical feedstock sustainably. Recently, studies have shown that two‐dimensional metal carbides and nitrides (MXenes) can be promising CO2RR electrocatalysts due to the alternating −C and −H coordination with intermediates that decouples scaling relations seen on transition metal catalysts. However, further by tuning the electronic and surface structure of MXenes it should still be possible to reach higher turnover number and selectivities. To this end, defect engineering of MXenes for electrochemical CO2RR has not been investigated to date. In this work, first‐principles modelling simulations are employed to systematically investigate CO2RR on M2XO2‐type MXenes with transition metal and carbon/nitrogen vacancies. We found that the −C‐coordinated intermediates take the form of fragments (e. g., *COOH, *CHO) whereas the −H‐coordinated intermediates form a complete molecule (e. g., *HCOOH, *H2CO). Interestingly, the fragment‐type intermediates become more strongly bound when transition‐metal vacancies are present on most MXenes, while the molecule‐type intermediates are largely unaffected, allowing the CO2RR overpotential to be tuned. The most promising defective MXene is Hf2NO2 containing Hf vacancies, with a low overpotential of 0.45 V. More importantly, through electronic structure analysis it could be observed that the Fermi level of the MXene changes significantly in the presence of vacancies, indicating that the Fermi level shift can be used as an ideal descriptor to rapidly predict the catalytic performance of defective MXenes. Such an evaluation strategy is applicable to other catalysts beyond MXenes, which could enhance high throughput screening efforts for accelerated catalyst discovery.

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Polymer-based electrolytes have attracted ever-increasing attention for solid-state batteries due to their excellent flexibility and processability. Among them, poly­(vinylidene difluoride) (PVDF)-based electrolytes with high ionic conductivity, wide electrochemical stability window, and good mechanical properties show great potential and have been widely investigated by using different Li salts, solvents, and inorganic fillers. Here, we report the influence of the molecular weight of PVDF itself on the electrochemical properties of the electrolytes by using two kinds of common PVDF polymers, i.e., PVDF 761 and 5130. Our results demonstrate that the electrolyte with a larger molecular weight (PVDF 5130) has a denser structure and lower crystallinity, and thus much better electrochemical performance, than one with a smaller molecular weight (PVDF 761). With PVDF 5130, the LiFePO4-based solid-state cells present a steady cycling performance with a capacity retention of 85% after 1000 cycles at 1 C and 30 °C. The cycle life of the LiCoO2-based solid-state cells is also extended by using PVDF 5130.

With the increasing strategies aimed at repressing shuttle problems in the lithium–sulfur battery, dissolved contents of polysulfides are significantly reduced. Except for solid-state Li2S2 and Li2S, aggregated phases of polysulfides remain unexplored, especially in well confined cathode material systems. Here, we report a series of nanosize polysulfide clusters and solid phases from an atomic perspective. The calculated phase diagram and formation energy evolution process demonstrate their stabilities and cohesive tendency. It is interesting to find that Li2S6 can stay in the solid state and contains short S3 chains, further leading to the unique stability and dense structure. Simulated electronic properties indicate reduced band gaps when polysulfides are aggregated, especially for solid phase Li2S6 with a band gap as low as 0.47 eV. Their dissolution behavior and conversion process are also investigated, which provides a more realistic model and gives further suggestions on the future design of the lithium–sulfur battery.

The interaction between spin and charge degrees of freedom offers a powerful tool to manipulate magnetization in memories by the current induced spin–orbit torque. This novel phenomenon, conventionally existing in semiconductors and metallic systems, has recently been observed in transition metal oxides, exhibiting a surprising large spin-Hall angle. In this Perspective, we will review recent research progress in the spin–charge conversion in transition metal oxides, the remaining challenges, and new opportunities. We will first briefly summarize recent progress in the spin–charge conversion in representative transition metal oxides, including SrIrO3, SrRuO3, and IrO2, along with other materials predicted by calculations. Next, we will survey the possible candidate materials in the family of transition metal oxides. Recent advances in the growth of SrIrO3 films will be reviewed along with the implications on the study of the spin-Hall effect. We will also discuss other promising candidates that could serve as the spin source, including films of pyrochlore and delafossite oxides as well as oxide heterostructures.

Complex oxides hosting 4d and 5d cations with significant spin–orbit coupling have recently been shown as promising materials for efficient spin‐charge interconversion. Through interfacing 4d and 5d oxides with magnet layers, a large spin–orbit torque (SOT) is reported. However, a room‐temperature SOT switching of perpendicular magnetization by using these oxides, which is essential for spintronic devices, is not demonstrated. Here, this is addressed yet missing aspect by studying heterostructures comprised of two representative complex oxides (4d SrRuO3 and 5d SrIrO3) and a compensated ferrimagnet FeGd with perpendicular magnetic anisotropy. A room temperature current‐induced SOT switching of perpendicular magnetization in both SrRuO3/FeGd and SrIrO3/FeGd bilayers, with the critical switching current density on the order of 106 A cm−2 is demonstrated. The SOT efficiencies of SrRuO3 and SrIrO3 are further quantified by using harmonic Hall voltage measurements. The results suggest that the strongly correlated oxides could be another promising platform for enabling energy‐efficient spin‐orbitronic applications.