Searching for highly efficient, stable, and cost-effective electrocatalysts for water splitting and oxygen reduction reaction (ORR) is critical for renewable energies, yet it remains a great challenge. Here, by performing an unbiased structural search and first-principles calculations, the electrocatalytic performance of the emerging 2D transitional-metal carbides, MC 2 (M represents the transition metal of Ti, V, Nb, Ta, and Mo, C is carbon), is systematically investigated. Owing to their super stability and outstanding electronic conductivity, fast charge transfer kinetics is allowed during catalysis. Specifically, NbC 2 , TaC 2 , and MoC 2 possess excellent hydrogen evolution reaction (HER) performance under the reaction by the Volmer-Heyrovsky mechanism. Moreover, taking advantage of the dual-active-site catalytic mechanism for oxygen evolution reaction (OER) and ORR over traditional single-active-site mechanism, TaC 2 presents promising bifunctional electrocatalytic activity with a low overpotential of 0.06 and 0.37 V for HER and ORR, respectively. Meanwhile, the low overpotential endows MoC 2 remarkable multifunctional electrocatalytic performance in overall water splitting (0.001 V for HER, 0.45 V for OER) and ORR (0.47 V). These intriguing results demonstrate the robust applicability of MC 2 monolayers as effective electrocatalysts.

Searching for highly efficient and eco-friendly photocatalysts for water splitting is essential for renewable conversion and storage of inexhaustible solar energy but remains a great challenge. Herein, based on the new emerging two-dimensional (2D) material of MoSi2N4, we report novel Janus MoSiGeN4 and WSiGeN4 structures with excellent stabilities and great potentials in photocatalytic applications through first-principles calculations. Comprehensive studies show that MoSi2N4, MoSiGeN4, and WSiGeN4 exhibit semiconductor characteristics with an indirect gap, appropriate band gaps, and strong optical absorbance in the visible spectrum. Excitingly, by constructing Janus structures, an intrinsic electric field is realized that enhances the spatial separation and anisotropic migration of photoexcited electrons and holes. Further, this strategy can also alter the band alignment to provide an adequate photoexcited carrier driving force for water redox reactions. Moreover, the surface N vacancy can effectively lower the energy demand of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) so that the catalytic process can be self-sustained under the potential provided by the photocatalyst alone. Particularly, the overall water splitting can proceed simultaneously and spontaneously on the surface of MoSiGeN4 and WSiGeN4 when pH is 3 or ≥8, respectively. These explorations offer new prospects for the design of highly efficient photocatalysts.

MoxCy monolayers and their potential application as anodes for LIBs/SIBs.

Spider silk fibers (SSF) have a hierarchical structure composed of proteins with highly repetitive sequences and biomineralization is sophisticated in hierarchical organic-inorganic constructions. By using inorganic hydroxyapatite (HAP) and organic polyvinyl alcohol (PVA) to simulate the rigid crystalline and flexible amorphous protein blocks of SSF, respectively, biomimetic mineralization is herein attempted for the large-scale preparation of SSF-like macrofibers with a hierarchical ordered structure, a superhigh tensile strength of 949 ± 38 MPa, a specific toughness of 296 ± 12 J g −1 , and a stretch ability of 80.6%. The hybrid macrofibers consist of microfibers, and their outstanding performance (e.g., extreme tolerance to temperatures ranging from −196 to 80 °C and superior ability to inhibit the transverse growth of cracks) is attributed to the hierarchical arrangement as well as the organic-inorganic integrated structure within the oriented mineralized polymer chains. The biomineralization-inspired technique provides a promising tactic that can be used to synthesize functional organicinorganic fibers that are structurally complex and, furthermore, industrially manufacture SSF-like artificial fibers with a supertoughness.

Achieving high-performance electroluminescence with EQE of 7.20% and CIEy ∼ 0.06 based on bipolar materials with intercrossed excited state characteristics.

Ionic oligomers and their crosslinking implies a possibility to produce novel organic–inorganic composites by copolymerization. Using organic acrylamide monomers and inorganic calcium phosphate oligomers as precursors, uniformly structured polyacrylamide (PAM)‐calcium phosphate copolymer is prepared by an organic–inorganic copolymerization. In contrast to the previous PAM‐based composites by mixing inorganic components into polymers, the copolymerized material has no interphase boundary owing to the homogenous incorporation of the organic and inorganic units at molecular level, resulting in a complete and continuous hybrid network. The participation of the ionic binding effect in the crosslinking process can substantially improve the mechanical strength; the copolymer can reach a modulus and hardness of 35.14±1.91 GPa and 1.34±0.09 GPa, respectively, which are far superior to any other PAM‐based composites.

High‐strength flexible inorganic paper with fire‐resistant and adiabatic properties is highly demanded in various high‐temperature applications. However, constructing inorganic paper that not only has high strength and high flexibility at room temperature but also can prevent the high‐temperature‐induced friability is still a great challenge. Inspired by the hierarchical structure and excellent mechanical properties of the tooth enamel, we have developed a systematic approach for the bottom‐up fabrication of multi‐hierarchical fire‐resistant hydroxyapatite (HAP) nanowire paper with balanced tensile strength and flexibility that includes four steps: (1) the synthesis of monodisperse HAP nanowires from the molecular level to the nanoscale; (2) the self‐assembly of HAP nanowires into long fibers and two‐dimensional (2D) nanowire networks from the nanoscale to the mesoscale; (3) the layered assembly of 2D nanowire networks into the highly flexible high‐strength fire‐resistant paper from the mesoscale to the macroscale; (4) reinforcing the HAP nanowire paper with inorganic additives to enhance the tensile strength and to overcome the high‐temperature‐induced pulverization. By adopting this strategy, the mechanical properties of the fire‐resistant HAP nanowire paper are greatly improved. The experimental results show that the tensile strength of the as‐prepared HAP nanowires‐based inorganic paper is greatly enhanced to ≈15 MPa, which is close to that of the commercial copying paper, and the A4‐sized HAP nanowires‐based inorganic paper is highly flexible and can be directly printed using a commercial printer. Owing to the synergistic effect of all components and the unique hierarchical structure, the as‐prepared fire‐resistant HAP nanowire paper can also preserve well its high flexibility even under high‐temperature conditions.

In article number 2000570, Jian Zhou, Zhimei Sun, and Yadong Yu propose a series of novel MXene-derived 2D transition metal carbides, which possess superior stability under acidic solutions and excellent electrical conductivity. The new-emerging 2D materials can serve as efficient, multifunctional electrocatalysts for hydrogen evolution reactions, oxygen evolution reactions, and oxygen reduction reactions.