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Developing highly active and durable electrocatalysts for acidic oxygen evolution reaction remains a great challenge due to the sluggish kinetics of the four-electron transfer reaction and severe catalyst dissolution. Here we report an electrochemical lithium intercalation method to improve both the activity and stability of RuO 2 for acidic oxygen evolution reaction. The lithium intercalates into the lattice interstices of RuO 2 , donates electrons and distorts the local structure. Therefore, the Ru valence state is lowered with formation of stable Li-O-Ru local structure, and the Ru–O covalency is weakened, which suppresses the dissolution of Ru, resulting in greatly enhanced durability. Meanwhile, the inherent lattice strain results in the surface structural distortion of Li x RuO 2 and activates the dangling O atom near the Ru active site as a proton acceptor, which stabilizes the OOH* and dramatically enhances the activity. This work provides an effective strategy to develop highly efficient catalyst towards water splitting. While water splitting in acid offers higher operational performances than in alkaline conditions, there are few high-activity, acid-stable oxygen evolution electrocatalysts. Here, authors examine electrochemical Li intercalation to improve the activity and stability of RuO 2 for acidic water oxidation.

Critical barriers to layered Ni-rich cathode commercialisation include their rapid capacity fading and thermal runaway from crystal disintegration and their interfacial instability. Structure combines surface modification is the ultimate choice to overcome these. Here, a synchronous gradient Al-doped and LiAlO 2 -coated LiNi 0.9 Co 0.1 O 2 cathode is designed and prepared by using an oxalate-assisted deposition and subsequent thermally driven diffusion method. Theoretical calculations, in situ X-ray diffraction results and finite-element simulation verify that Al 3+ moves to the tetrahedral interstices prior to Ni 2+ that eliminates the Li/Ni disorder and internal structure stress. The Li + -conductive LiAlO 2 skin prevents electrolyte penetration of the boundaries and reduces side reactions. These help the Ni-rich cathode maintain a 97.4% cycle performance after 100 cycles, and a rapid charging ability of 127.7 mAh g −1 at 20 C. A 3.5-Ah pouch cell with the cathode and graphite anode showed more than a 500-long cycle life with only a 5.6% capacity loss. The commercialisation of promising Ni-rich cathodes is limited by capacity fading and thermal runaway. Here, the authors design a gradient Al-doped and LiAlO 2 -coated LiNi 0.9 Co 0.1 O 2 cathode, which addresses the crystal degradation and interfacial instability and thus improves the cycle and thermal stabilities.

In this introduction we argue that taking a topological approach to care can encourage us to understand both how caring relations and practices are produced and the forms they take as they shift and transform. We suggest that thinking topologically about the articles collected in this special section highlights how caring actions and practices ripple out into the world beyond immediate caring relationships and the immediate moment. Responding to a call within geographies of care to be thoroughly attuned to the placed-ness of caring relations and to contribute work that theorises from places beyond the global north, the papers in this collection are situated in diverse geographical and cultural contexts, thoroughly contextualised in place and time and explore complicated relations that shape and challenge care. The geographies of care presented in this collection are a sampling of the diverse forms of care that are possible and, we argue, that by employing a topological approach to care, the possibility of what care can be and mean multiplies and expands.

Layered materials have attracted tremendous interest for accessing two-dimensional structures. Materials such as graphite or transition metal dichalcogenides, in which the layers are held together by van der Waals interactions, can be exfoliated through a variety of processes in a manner that retains the structure and composition of the monolayers, but this has proven difficult for solids with stronger interlayer interactions. Here, we demonstrate the exfoliation of AgCrS2, a member of the AMX2 family (where A is a monovalent metal, M is a trivalent metal and X is a chalcogen), through intercalation with tetraalkylammonium cations, chosen for their suitable redox potential. The as-exfoliated nanosheets consist of Ag layers sandwiched between two CrS2 layers, similar to their structure in the bulk. They show superionic behaviour at room temperature, with an ionic conductivity of 33.2 mS cm−1 at 298 K that originates from Ag+ ions rapidly hopping between neighbouring tetrahedral interstices; in the bulk, this behaviour is only observed above 673 K.Layered materials held together by weak interactions can be exfoliated into monolayers that retain the structure and composition of their bulk counterpart, but this has remained challenging to achieve for non-van der Waals materials. Now, AgCrS2 has been exfoliated into such [CrS2]Ag[CrS2] nanosheets through intercalation with tetraalkylammonium cations chosen for their suitable redox potential. The nanosheets show superionic behaviour at room temperature.

HighlightsDesign and fabrication of MXene-based soft actuators with angle-independent structural color.The nanostructured MXene can not only facilitate the formation of short-range ordered 3D amorphous photonic crystals, but also help significantly improve structural color saturation.The soft actuators exhibit brilliant angle-independent structural color, ultrafast actuation and recovery speeds in response to vapor.In nature, many living organisms exhibiting unique structural coloration and soft-bodied actuation have inspired scientists to develop advanced structural colored soft actuators toward biomimetic soft robots. However, it is challenging to simultaneously biomimic the angle-independent structural color and shape-morphing capabilities found in the plum-throated cotinga flying bird. Herein, we report biomimetic MXene-based soft actuators with angle-independent structural color that are fabricated through controlled self-assembly of colloidal SiO2 nanoparticles onto highly aligned MXene films followed by vacuum-assisted infiltration of polyvinylidene fluoride into the interstices. The resulting soft actuators are found to exhibit brilliant, angle-independent structural color, as well as ultrafast actuation and recovery speeds (a maximum curvature of 0.52 mm−1 can be achieved within 1.16 s, and a recovery time of ~ 0.24 s) in response to acetone vapor. As proof-of-concept illustrations, structural colored soft actuators are applied to demonstrate a blue gripper-like bird’s claw that can capture the target, artificial green tendrils that can twine around tree branches, and an artificial multicolored butterfly that can flutter its wings upon cyclic exposure to acetone vapor. The strategy is expected to offer new insights into the development of biomimetic multifunctional soft actuators for somatosensory soft robotics and next-generation intelligent machines.

This brief discussion piece focuses on geographies of care, providing a commentary to the special section on “Interstices of care,” edited by Kelsey Hanrahan and Christine Smith. My attempt is to pull together some resonant themes from the individual contributions and to consider what the collection may offer for further research in geography and neighbouring research fields.

The fresh and rheological properties of alkali mortars activated by blast furnace slag (BFS) were investigated. Consistency tests, squeeze flow, dropping ball, mass density in the hardened state, incorporated air, and water retention were performed. Mortars were produced with the ratio 1:2:0.45 (binder:sand:water), using not only ordinary Portland cement for control but also BFS, varying the sodium content of the activated alkali mortars from 2.5 to 15%. The results obtained permitted understanding that mortars containing 2.5 to 7.5% sodium present a rheological behavior similar to cementitious mortars by the Bingham model. In turn, the activated alkali mortars containing 10 to 15% sodium showed a very significant change in the properties of dynamic viscosity, which is associated with a change in the type of model, starting to behave similar to the Herschel–Bulkley model. Evaluating the properties of incorporated air and water retention, it appears that mortars containing 12.5% and 15% sodium do not have compatible properties, which is related to the occupation of sodium ions in the interstices of the material. Thus, it is concluded that the techniques used were consistent in the rheological characterization of activated alkali mortars.

We consider the multidirectional swelling and drying of hydrogels formed from super-absorbent polymers and water, focusing on the elastic deformation caused by differential swelling. By modelling hydrogels as instantaneously incompressible, linear-elastic materials and considering situations in which there can be large isotropic strains (arising from swelling) while deviatoric strains remain small, it is possible to describe accurately a wider range of gel states than traditional linear elastic theories allow. An equation is derived relating the displacement field to the polymer fraction in such hydrogels, permitting the shape of the swelling gel to be determined as it evolves in time, using the formulation of Part 1 to find the local polymer fraction. We discuss the boundary conditions to be applied at the surfaces of a gel, both on the bulk elastic stress and on the pervadic (pore) pressure in the interstices. Similarities between the equation for the displacements and the equations of classical plate theory are investigated by considering a model problem of a slender cylinder with its base immersed in water drying by evaporation into the surrounding air. In this problem, there is differential drying along the axis of the cylinder, as the base remains swollen while the top dries. The results of our displacement formulation agree qualitatively with experiments that we have conducted, and provide a physical interpretation of the forced biharmonic equation describing the displacement field.

This article demonstrates that the social categories of indigenous and white-mestizo are essentialist, reductionist, and therefore insufficient to encompass the diverse expressions of identity that exist. Understood through fluid and interchangeable lines, a new category is proposed: the border identity. Exemplified through the ethnic communes of the parish of Manglaralto, in the province of Santa Elena, Ecuador, this new category is intended to reconcile opposites and dismantle existing binaries to better capture the multifaceted social diversity of different sociocultural expressions. Previously agricultural, these communes have been transformed into internationally known tourist destinations, while being denied recognition of their ethnic identity due to the acculturations they have been subject to through various historical periods. Their members are labeled as acculturated indigenous or cholos, too mestizo to be considered indigenous and too indigenous to be considered mestizo. Qualitative methods such as participant observations, informal conversations, and semi-structured interviews were used for the ethnographic work spanning more than four years. The data collected and analyzed data showed how these communities, through constant negotiation with the white-mestizo world, achieve autonomy even within deeply dependent relationships. The study illustrates how they operate from an interstice, an intermediate space, which complicates their placement within existing social categories, underscoring the need to conceptualize new social categories beyond traditional binaries. El objetivo de este artículo es mostrar que las categorías sociales de lo indígena y de lo blanco-mestizo son esencialistas, reduccionistas y, por lo tanto, insuficientes para agrupar en ellas las diversas expresiones identitarias que existen. Como consecuencia de esto, se propone una nueva categoría: lo fronterizo, que se comprende a partir de líneas fluidas e intercambiables, como un intento de conjugar los opuestos y desmantelar los binarismos existentes para, de esta manera, poder captar la diversidad social multifacética de diferentes expresiones socioculturales. Aquello se ejemplifica mediante un caso concreto: las comunas étnicas de la parroquia de Manglaralto, situadas en la provincia de Santa Elena, Ecuador. Agrícolas antes, hoy han sido convertidas en lugares turísticos, conocidos a nivel internacional. A estas comunas se les niega el reconocimiento de su identidad étnica, resultado de las aculturaciones que han vivido a lo largo de varios períodos históricos. Sus miembros son declarados indígenas aculturados o cholos, porque son demasiado mestizos para ser indígenas y demasiado indígenas para ser mestizos. Para el trabajo etnográfico, durante un lapso de más de cuatro años, se utilizaron métodos cualitativos, como las observaciones participantes, las conversaciones informales y las entrevistas semiestructuradas. Los datos levantados y analizados más adelante mostraron cómo estas comunidades, por medio de una negociación constante con el mundo de los blanco-mestizos, adquieren autonomía aun en relaciones de profundas dependencias. Se muestra cómo actúan desde un intersticio, un espacio intermedio, que dificulta otorgarles un lugar dentro de las categorías sociales existentes. Con ello, se hace evidente la necesidad de pensar en nuevas categorías sociales fuera de los binarismos. O objetivo deste artigo é mostrar que as categorias sociais do indígena e do branco-mestiço são essencialistas, reducionistas e, portanto, insuficientes para agrupar as diversas expressões identitárias existentes. Como consequência, propõe-se uma nova categoria: o fronteiriço, que é entendido a partir de linhas fluidas e intercambiáveis, como tentativa de conjugar opostos e desfazer os binarismos existentes a fim de capturar a diversidade social multifacetada de diferentes expressões socioculturais. Isso é exemplificado por um caso concreto: as comunidades étnicas da paróquia de Manglaralto, localizadas na província de Santa Elena, Equador. Antes agrícolas, hoje elas foram convertidas em locais turísticos conhecidos internacionalmente. A essas comunidades é negado o reconhecimento de sua identidade étnica, resultado da aculturação que sofreram ao longo de vários períodos históricos. Seus membros são declarados indígenas aculturados ou cholos, porque são mestiços demais para serem indígenas e indígenas demais para serem mestiços. Para o trabalho etnográfico, em um período de mais de quatro anos, foram usados métodos qualitativos, como observações participantes, conversas informais e entrevistas semiestruturadas. Os dados coletados e analisados a seguir mostram como essas comunidades, por meio da negociação constante com o mundo dos brancos e mestiços, adquirem autonomia mesmo em relacionamentos profundamente dependentes. Evidencia-se como elas agem a partir de um interstício, um espaço intermediário, que torna difícil a atribuição de um lugar dentro das categorias sociais existentes. Com isso, fica evidente a necessidade de se pensar em novas categorias sociais fora dos binarismos.

Assemblies of slender structures forming brushes are common in daily life from sweepers to pastry brushes and paintbrushes. These types of porous objects can easily trap liquid in their interstices when removed from a liquid bath. This property is exploited to transport liquids in many applications, ranging from painting, dip-coating and brush-coating to the capture of nectar by bees, bats and honeyeaters. Rationalising the viscous entrainment flow beyond simple scaling laws is complex due to the multiscale structure and the multidirectional flow. Here, we provide an analytical model, together with precision experiments with ideal rigid brushes, to fully characterise the flow through this anisotropic porous medium as it is withdrawn from a liquid bath. We show that the amount of liquid entrained by a brush varies non-monotonically during the withdrawal at low speed, is highly sensitive to the different parameters at play and is very well described by the model without any fitting parameter. Finally, an optimal brush geometry maximising the amount of liquid captured at a given retraction speed is derived from the model and experimentally validated. These optimal designs open routes towards efficient liquid-manipulating devices.