Few-layered exfoliated black phosphorus (EBP) has attracted surging interest for electronics, optoelectronics, and catalysis. As compared to excellent progress in electronic and optoelectronic applications, very few reports are available for electrocatalysis by metal-free EBPs. Herein, we couple solutionprocessable ultrathin EBP nanosheets with higher Fermi level of N-doped graphene (NG) into a new metal-free 2D/2D heterostructure (EBP@NG) with well-designed interfaces and unique electronic configuration, as efficient and durable bifunctional catalysts toward hydrogen evolution and oxygen evolution reactions (HER/OER) for overall water splitting in alkaline media. By rational interface engineering, the synergy of EBP and NG is fully exploited, which not only improves the stability of EBP, but also effectively modulates electronic structures of each component to boost their intrinsic activities. Specifically, due to the lower Fermi level of EBP relative to NG, their electronic interaction induces directional interfacial electron transfer, which not only enriches the electron density over EBP and optimizes H adsorption/desorption to promote HER, but also introduces abundant positively charged carbon sites on NG and provides favorable formation of key OER intermediates (OOH*) to improve OER energetics. Thus, despite that pure EBP or NG alone has poor or negligible activity, EBP@NG achieves remarkably enhanced bifunctional HER/ OER activities, along with an excellent durability. This endows an optimized electrolyzer using EBP@NG as anode and cathode with a low cell voltage of 1.54 V at 10 mA cm −2 , which is smaller than that of the costly integrated Pt/C@RuO 2 couple (1.60 V).

Photonic crystals, which are materials with periodic dielectric constants on the submicroscale, have been the focus of research for an extended period. Photonic soft materials have been extensively developed for use as colorimetric indicators and mechanochromic sensors, but their limited mechanical properties and molding characteristics only suitable for films restrict their practical implementation. Herein we report an approach to synthesize highly stretchable photonic soft materials based on a hydrogel system that is cross-linked by a crystalline colloidal array. The intrinsic inhomogeneous submicroscale structure is exploited for effective reinforcement in the multiphase system of the photonic crystals. The photonic hydrogels exhibit a high deformation capacity, with a stretching deformation above 2800% and compression above 98%. The gel has a full-color tunable range and shows 460 nm photonic shifts that can be reversibly actuated by a small compressive stress (kPa level) and can be ink-written to form patterns and freestanding structures. Mechanochromic sensors are constructed based on the three-dimensional and two-dimensional Bragg diffraction of the gel. Owing to its mechanical strength, formability, and tunable colors, the gel can be used in wearable optical devices, colorimetric tactile sensors, and full-color displays.

Nitrogen‐rich porous carbons (NPCs) are the leading cathode materials for next‐generation Zn–air and Li–S batteries. However, most existing NPC suffers from insufficient exposure and harnessing of nitrogen‐dopants (NDs), constraining the electrochemical performance. Herein, by combining silica templating with in situ texturing of metal–organic frameworks, a new bifunctional 3D nitrogen‐rich carbon photonic crystal architecture of simultaneously record‐high total pore volume (13.42 cm3 g−1), ultralarge surface area (2546 m2 g−1), and permeable hierarchical macro‐meso‐microporosity is designed, enabling sufficient exposure and accessibility of NDs. Thus, when used as cathode catalysts, the Zn–air battery delivers a fantastic capacity of 770 mAh gZn−1 at an unprecedentedly high rate of 120 mA cm−2, with an ultrahigh power density of 197 mW cm−2. When hosting 78 wt% sulfur, the Li–S battery affords a high‐rate capacity of 967 mAh g−1 at 2 C, with superb stability over 1000 cycles at 0.5 C (0.054% decay rate per cycle), comparable to the best literature value. The results prove the dominant role of highly exposed graphitic‐N in boosting both cathode performances.

1wileyonlinelibrary.com on crystalline and molecular engineering could turn the band gap of g-C 3 N 4 by element doping, [4] using different precursors, [5][6][7][8][9] introducing crystal defects or amorphous structure, [3,10,11] forming carbon vacancies, [12] fabricating heterojunction composites, [13][14][15] and so on. Structural regulation mainly focused on increasing specific surface area, [16][17][18][19][20][21] typically making mesoporous by templates with high specific surface area. [16,17,20,21] However, most of studies reported focused on g-C 3 N 4 in the powder form due to the contradiction between the highly open framework and the insufficient mechanical strength. Some recent progresses have been made to achieve 3D macroform g-C 3 N 4 based on robust substrate, [19] but major challenges remain to develop a substrate-free g-C 3 N 4 film with high photocatalytic activity. Photonic crystals (PCs) are materials with spatially periodic variation of the dielectric permittivity on the order of the wavelength of light. The propagation of light within a certain frequency range is forbidden in a certain crystal direction within a certain spectrum regime, namely photonic stopband. [22,23] Special properties of PCs, such as inhibition of spontaneous emission, [24][25][26] slow light, and amplified photon absorption/emission, [27][28][29][30] provide numerous possibilities for "photon management" applications. Thus introducing PC structure is a promising strategy for promoting photocatalytic activity of photocatalyst and the performance in optoelectronic devices. [27][28][29][30][31][32][33] Consequently, if g-C 3 N 4 is fabricated in a PC form, the spontaneous emission by the recombination of photogenerated carriers could be inhibited and the photocatalytic activity could benefit from the bicontinous network with increased visible light absorption via slow photon effects.Inspired by considerations above, herein we demonstrate a general solution approach to tackle the challenge via a freestanding colloidal crystal templating method (see Scheme 1). Freestanding, highly ordered, crack-free silica PCs are generated by evaporative-vertical deposition. Subsequently, the calcination of the precursor dicyandiamide (DCDA) followed by removal of silica PCs generates highly uniform macroscopic g-C 3 N 4 PC films. The resultant freestanding g-C 3 N 4 PCs possesses a 3D interconnected network with tunable photonic stop band, exhibiting significantly improved photocatalytic activity in photodegrading and water splitting under visible light. Freestanding Graphitic Carbon Nitride Photonic Crystals for Enhanced PhotocatalysisLu Sun, Meijia Yang, Jianfeng Huang, Dingshan Yu, Wei Hong,* and Xudong Chen* Graphitic carbon nitride (g-C 3 N 4 ) has attracted tremendous attention in photocatalysis due to its extraordinary features, such as good thermal and chemical stability, metal-free composition, and easy preparation. However, the photocatalytic performance of g-C 3 N 4 is still restricted by the limited surface area, inefficient v...

Directional interfacial charge transfer doping was used to significantly boost the water oxidation performance of pure carbon nanotubes.