performance of metal-air batteries (such as energy efficiency, output power density, and stability) is still restricted by the kinetically sluggish oxygen reaction on the air-cathode, which puts forward urgent requirements for highly active and durable oxygen reaction catalysts. [3][4][5] To date, various catalysts with high activity, good durability, and low cost, such as metal-free heteroatom-doped carbon materials [6][7][8][9][10][11][12] and ternary Me-N x -C materials (Me = transition metals, N = nitrogen, C = carbon), [13,14] have been explored as potential alternatives of conventional noble metal based catalysts.Ternary Me-N x -C materials, especially those with atomical dispersion of Me-N x -C sites, have been demonstrated to show superior catalytic performance to Pt/C, which can be ascribed to the Me-N x -C moieties-induced effective modification of the local electronic structure and the corresponding optimization of the intermediate adsorption. [15][16][17][18][19] To prepare highly active Me-N x -C materials, complicated structure design strategies for precursors are generally employed, such as polymer-encapsulated structure, [20] metal (hydr)oxides @polymer core-shell structure, [21] copolymer structure, [22] zeolitic imidazolate framework-encapsulated structure, [23] and polymerizable ionic liquid functionalized with nitrate groups. [24] Therefore, developing an effective and versatile strategy to controllably synthesize catalysts with atomically-dispersed Me-N x -C active sites would be of great significance and challenge.Silk, as an abundant protein biomaterial, has been developed as a green and promising precursor to prepare intrinsically N-doped carbon materials through simple thermal treatment, which is attributed to the amino-group-rich chemical structure and the β-sheet structure of silk fibroin. [25][26][27] Owing to the intrinsic N-doping, silk-derived carbon materials have been investigated for oxygen reduction reaction (ORR), which generally showed inferior ORR performance because of their low specific surface area and inadequate active sites. [28,29] Actually, natural silk fibroin can be dissolved in high-concentration transition metal salt solution, and then regenerated into 2D lamellar-like layer structure due to the self-assembly of hydrophobic and hydrophilic blocks of silk fibroin. [30] After a thermal annealing process at a temperature above the glass transition temperature, the regenerated silk fibroin would retain Controlled synthesis of highly efficient, stable, and cost-effective oxygen reaction electrocatalysts with atomically-dispersed Me-N x -C active sites through an effective strategy is highly desired for high-performance energy devices. Herein, based on regenerated silk fibroin dissolved in ferric chloride and zinc chloride aqueous solution, 2D porous carbon nanosheets with atomically-dispersed Fe-N x -C active sites and very large specific surface area (≈2105 m 2 g −1 ) are prepared through a simple thermal treatment process. Owing to the 2D porous structure with large s...

Flexible and rechargeable Zn−air batteries, because of their high energy density, low cost, and environmental and human benignity, are one kind of the most attractive energy systems for future wearable electronics. The development of high-performance rechargeable Zn−air batteries depends on the synthesis of highly efficient and highly stable electrocatalysts for the oxygen reduction reaction/oxygen evolution reaction (ORR/OER). Herein, a silk-derived defect-rich and nitrogen-doped nanocarbon electrocatalyst [SilkNC/Ketjenblack (KB)] is reported. The SilkNC/KB is synthesized by pyrolyzing commercially available porous KB carbon impregnated with silk fibroin. It exhibits remarkable electrocatalytic activities and long-term stability for the ORR/OER, enabling its applications in high-performance liquid and solid rechargeable Zn−air batteries. Particularly, the all-solid-state Zn−air battery based on SilkNC/KB exhibits good flexibility and remarkable charge/discharge stability, enabling its promising applications in wearable and energy-efficient batteries.

One of the important objectives in fuel-cell technology is to improve the activity and reduce the loading of Pt for hydrogen-evolution electrocatalysis. Here, an oxidative etching strategy of stacking faults is developed to prepare Pt­AgCo nanosheets by element-specific anisotropic growth. Sophisticated use of defects in crystal growth allows tailoring the morphology and interfacial polarization to improve catalytic performance of nanosheets for the hydrogen-evolution reaction. Systematic studies reveal that the presence of the stacking faults may be the knob for the formation of nanosheets. In particular, the chemical composition of nanosheets is potentially the key for altering the hydrogen-evolution reaction. As a result, the Pt­AgCo-II ultrathin nanosheets possess useful HER properties, achieving a current density up to 705 mA cm–2 at a potential of −400 mV.

We report here a facile synthesis of graphene decorated with in-plane boron nitride domains (BN-G) and uncover that the formation of BN domains in graphene is critical for engineering the band gap and resulting in an improved activity for photocatalytic hydrogen generation. ABSTRACT: Band gap opening and engineering is one of the tremendous aims in developing novel materials for photocatalytic hydrogen generation. We report here a facile synthesis of graphene decorated with in-plane boron nitride domains by controlling both the doping sequence of heteroatoms and the oxygen content of graphene precursor, 3 showing significant differences in the doping pattern compared with B and/or N singleor co-doped graphene. We uncover that the formation of BN domains in graphene is critical for engineering the band gap and resulting in an improved activity for photocatalytic hydrogen generation in the absence of any photosensitizer. This work paves the way for the rational design and construction of graphene-based photocatalysts for efficient photocatalysis.

We present a new two-step synthetic route combining the concepts of crystal symmetry, seed ratio and oxidative etching that yields tetrametallic PtAgBiCo nanoplates.