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.