A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm−3, 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm−3, which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs.

The stabilization of transition metals as isolated centres on suitably tailored carriers with high density is crucial to exploit the technical potential of single-atom heterogeneous catalysts, enabling their maximized productivity in industrial reactors. Wet-chemical methods are best suited for practical applications due to their amenability to scale up. However, achieving single-atom dispersions at metal contents above 2 wt.% remains challenging. We introduce a versatile approach combining impregnation and two-step annealing to synthesize ultra-high-density single-atom catalysts (UHD-SACs) with unprecedented metal contents up to 23 wt.% for 15 metals on chemically-distinct carriers. Translation to an automated protocol demonstrates its robustness and provides a path to explore virtually unlimited libraries of mono or multimetallic catalysts. At the molecular level, characterization of the synthesis mechanism through experiments and simulations shows that controlling the bonding of metal precursors with the carrier via stepwise ligand removal prevents their thermally-induced aggregation into nanoparticles, ensuring atomic dispersion in the resulting UHD-SACs. The catalytic bene ts of UHD-SACs are demonstrated for the electrochemical reduction of CO 2 to CO over NiN 4 motifs on carbon.

Silicon is a promising anode material for lithium-ion and post lithium-ion batteries but suffers from a large volume change upon lithiation and delithiation. The resulting instabilities of bulk and interfacial structures severely hamper performance and obstruct practical use. Stability improvements have been achieved, although at the expense of rate capability. Herein, a protocol is developed which we describe as two-dimensional covalent encapsulation. Twodimensional, covalently bound silicon-carbon hybrids serve as proof-of-concept of a new material design. Their high reversibility, capacity and rate capability furnish a remarkable level of integrated performances when referred to weight, volume and area. Different from existing strategies, the two-dimensional covalent binding creates a robust and efficient contact between the silicon and electrically conductive media, enabling stable and fast electron, as well as ion, transport from and to silicon. As evidenced by interfacial morphology and chemical composition, this design profoundly changes the interface between silicon and the electrolyte, securing the as-created contact to persist upon cycling. Combined with a simple, facile and scalable manufacturing process, this study opens a new avenue to stabilize silicon without sacrificing other device parameters. The results hold great promise for both further rational improvement and mass production of advanced energy storage materials.

A unique MoS2@graphene nanocable with a novel contact model between MoS2 nanosheets and graphene has been developed for high-performance lithium storage.