Biomass-derived carbon materials have received extensive attention as electrode materials for energy storage devices, including electrochemical capacitors, lithium–sulfur batteries, lithium-ion batteries, and sodium-ion batteries.

Although various two-dimensional (2D) nanomaterials have been explored as promising capacitive materials due to their unique layered structure, their natural restacking tendency impedes electrolyte transport and significantly restricts their practical applications. Herein, we synthesize all-carbon layer-by-layer motif architectures by introducing 2D ordered mesoporous carbons (OMC) within the interlayer space of 2D nanomaterials. As a proof of concept, MXenes are selected as 2D hosts to design 2D–2D heterostructures. Further removing the metal elements from MXenes leads to the formation of all-carbon 2D–2D heterostructures consisting of alternating layers of MXene-derived carbon (MDC) and OMC. The OMC layers intercalated with the MDC layers not only prevent restacking but also facilitate ion diffusion and electron transfer. The performance of the obtained hybrid carbons as supercapacitor electrodes demonstrates their potential for upcoming electronic devices. This method allows to overcome the restacking and blocking of 2D nanomaterials by constructing ion-accessible OMC within the 2D host material.

The oxygen evolution reaction (OER) is a key process involved in energy and environment‐related technologies. An ideal OER electrocatalyst should show high exposure of active sites and optimal adsorption energies of oxygenated species. However, earth‐abundant transition‐metal‐based OER electrocatalysts still operate with sluggish OER kinetics. Here, a cation‐exchange route is reported to fabricate cobalt‐vanadium‐iron (oxy)hydroxide (CoV‐Fe0.28) nanosheets with tunable binding energies for the oxygenated intermediates. The formation of an amorphous/crystalline heterostructure in the CoV‐Fe0.28 catalyst boosts the exposure of active sites compared to their crystalline and amorphous counterparts. Furthermore, the synergetic interaction of Co, V, and Fe cations in the CoV‐Fe0.28 catalyst subtly regulates the local coordination environment and electronic structure, resulting in the optimal thermodynamic barrier for this elementary reaction step. As a result, the CoV‐Fe0.28 catalyst exhibits superior electrocatalytic activity toward the OER. A low overpotential of 215 mV is required to afford a current density of 10 mA cm−2 with a small Tafel slope of 39.1 mV dec−1, which outperforms commercial RuO2 (321 mV and 86.2 mV dec−1, respectively).

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Atomic-scale analysis of the cation valence state distribution will help to understand intrinsic features of oxygen vacancies (V ) inside metal oxide nanocrystals, which, however, remains a great challenge. In this work, the distribution of cerium valence states across the ultrafine CeO nanocubes (NCs) perpendicular to the {100} exposed facet is investigated layer-by-layer using state-of-the-art scanning transmission electron microscopy-electron energy loss spectroscopy. The effect of size on the distribution of Ce valence states inside CeO NCs is demonstrated as the size changed from 11.8 to 5.4 nm, showing that a large number of Ce cations exist not only in the surface layers, but also in the center layers of smaller CeO NCs, which is in contrast to those in larger NCs. Combining with the atomic-scale analysis of the local structure inside the CeO NCs and theoretical calculation on the V forming energy, the mechanism of size effect on the Ce valence states distribution and lattice expansion are elaborated: nano-size effect induces the overall lattice expansion as the size decreased to ≈5 nm; the expanded lattice facilitates the formation of V due to the lower formation energy required for the smaller size, which, in principle, provides a fundamental understanding of the formation and distribution of Ce inside ultrafine CeO NCs.