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The performance of electrocatalysts is critical for renewable energy technologies. While the electrocatalytic activity can be modulated through structural and compositional engineering following the Sabatier principle, the insufficiently explored catalyst-electrolyte interface is promising to promote microkinetic processes such as physisorption and desorption. By combining experimental designs and molecular dynamics simulations with explicit solvent in high accuracy, we demonstrated that dimethylformamide can work as an effective surface molecular pump to facilitate the entrapment of oxygen and outflux of water. Dimethylformamide disrupts the interfacial network of hydrogen bonds, leading to enhanced activity of the oxygen reduction reaction by a factor of 2 to 3. This strategy works generally for platinum-alloy catalysts, and we introduce an optimal model PtCuNi catalyst with an unprecedented specific activity of 21.8 ± 2.1 mA/cm²at 0.9 V versus the reversible hydrogen electrode, nearly double the previous record, and an ultrahigh mass activity of 10.7 ± 1.1 A/mg_Pt.

 

Compositionally complex oxides (CCOs) are an emerging class of materials encompassing high entropy and entropy stabilized oxides. These promising advanced materials leverage tunable chemical bond structure, lattice distortion, and chemical disorder for unprecedented properties. Grain boundary (GB) and point defect segregation to GBs are relatively understudied in CCOs even though they can govern macroscopic material properties. For example, GB segregation can govern local chemical (dis)order and point defect distribution, playing a critical role in electrochemical reaction kinetics, and charge and mass transport in solid electrolytes. However, compared with conventional oxides, GBs in multi-cation CCO systems are expected to exhibit more complex segregation phenomena and, thus, prove more difficult to tune through GB design strategies. Here, GB segregation was studied in a model perovskite CCO LaFe0.7Ni0.1Co0.1Cu0.05Pd0.05O3−x textured thin film by (sub-)atomic-resolution scanning transmission electron microscopy imaging and spectroscopy. It is found that GB segregation is correlated with cation reducibility—predicted by an Ellingham diagram—as Pd and Cu segregate to GBs rich in oxygen vacancies (VO··). Furthermore, Pd and Cu segregation is highly sensitive to the concentration and spatial distribution of VO·· along the GB plane, as well as fluctuations in atomic structure and elastic strain induced by GB local disorder, such as dislocations. This work offers a perspective of controlling segregation concentration of CCO cations to GBs by tuning reducibility of CCO cations and oxygen deficiency, which is expected to guide GB design in CCOs.

 

Confining materials to two-dimensional forms changes the behaviour of the electrons and enables the creation of new devices. However, most materials are challenging to produce as uniform, thin crystals. Here we present a synthesis approach where thin crystals are grown in a nanoscale mould defined by atomically flat van der Waals (vdW) materials. By heating and compressing bismuth in a vdW mould made of hexagonal boron nitride, we grow ultraflat bismuth crystals less than 10 nm thick. Due to quantum confinement, the bismuth bulk states are gapped, isolating intrinsic Rashba surface states for transport studies. The vdW-moulded bismuth shows exceptional electronic transport, enabling the observation of Shubnikov–de Haas quantum oscillations originating from the (111) surface state Landau levels. By measuring the gate-dependent magnetoresistance, we observe multi-carrier quantum oscillations and Landau level splitting, with features originating from both the top and bottom surfaces. Our vdW mould growth technique establishes a platform for electronic studies and control of bismuth’s Rashba surface states and topological boundary modes1,2,3. Beyond bismuth, the vdW-moulding approach provides a low-cost way to synthesize ultrathin crystals and directly integrate them into a vdW heterostructure. 

Recent studies have reported worldwide vegetation suppression in response to increasing atmospheric vapor pressure deficit (VPD). Here, we integrate multisource datasets to show that increasing VPD caused by warming alone does not suppress vegetation growth in northern peatlands. A site-level manipulation experiment and a multiple-site synthesis find a neutral impact of rising VPD on vegetation growth; regional analysis manifests a strong declining gradient of VPD suppression impacts from sparsely distributed peatland to densely distributed peatland. The major mechanism adopted by plants in response to rising VPD is the “open” water-use strategy, where stomatal regulation is relaxed to maximize carbon uptake. These unique surface characteristics evolve in the wet soil‒air environment in the northern peatlands. The neutral VPD impacts observed in northern peatlands contrast with the vegetation suppression reported in global nonpeatland areas under rising VPD caused by concurrent warming and decreasing relative humidity, suggesting model improvement for representing VPD impacts in northern peatlands remains necessary.

 

Ultra-wide bandgap (UWBG) semiconductors are promising for many applications, such as power electronics and deep-ultraviolet photonics. In this research, UWBG β-phase magnesium gallium oxide (MgGaO) thin films with a bandgap of 5.1 eV were grown using low-temperature homo-buffer layers in a plasma-assisted molecular beam epitaxy system. The role of the growth temperature and thickness of low-temperature buffer layer on the quality of the active layer was studied using x-ray diffraction and transmission electron microscopy and by analyzing the properties of metal–semiconductor–metal photodetector devices based on these films. It is found that lower buffer growth temperature at 300 °C leads to higher crystal quality of active layer. For the same low buffer growth temperature, different crystal quality in the active layer is attained with different buffer layer thickness. A buffer layer thickness at 40 nm has the best active layer quality with the highest photo current under 265 nm illumination and long decay time as a result of reduced recombination of photo-generated carriers through fewer defects in the active layer. 

Garnet‐type Li₇La₃Zr₂O₁₂(LLZO) solid‐state electrolytes hold great promise for the next‐generation all‐solid‐state batteries. An in‐depth understanding of the phase transformation during synthetic processes is required for better control of the crystallinity and improvement of the ionic conductivity of LLZO. Herein, the phase transformation pathways and the associated surface amorphization are comparatively investigated during the sol–gel and solid‐state syntheses of LLZO using in situ heating transmission electron microscopy (TEM). The combined ex situ X‐ray diffraction and in situ TEM techniques are used to reveal two distinct phase transformation pathways (precursors → La₂Zr₂O₇ → LLZO and precursors → LLZO) and the subsequent layer‐by‐layer crystal growth of LLZO on the atomic scale. It is also demonstrated that the surface amorphization surrounding the LLZO crystals is sensitive to the postsynthesis cooling rate and significantly affects the ionic conductivity of pelletized LLZO. This work brings up a critical but often overlooked issue that may greatly exacerbate the Li‐ion conductivity by undesired synthetic conditions, which can be leveraged to ameliorate the overall crystallinity to improve the electrochemical performance of LLZO. These findings also shed light on the significance of optimizing surface structure to ensure superior performance of Li‐ion conductors.