Exploring of new catalyst activation principle holds a key to unlock catalytic powers of cheap and earth‐abundant materials for large‐scale applications. In this regard, the vacancy defects have been ...proven to be effective to initiate catalytic active sites and endow high electrocatalytic activities. However, such electrocatalytically active defects reported to date have been mostly formed by anion vacancies. Herein, it is demonstrated for the first time that iron cation vacancies induce superb water splitting bifunctionality in alkaline media. A simple wet‐chemistry method is developed to grow ultrathin feroxyhyte (δ‐FeOOH) nanosheets with rich Fe vacancies on Ni foam substrate. The theoretical and experimental results confirm that, in contrast to anion vacancies, the formation of rich second neighboring Fe to Fe vacancies in δ‐FeOOH nanosheets can create catalytic active centers for both hydrogen and oxygen evolution reactions. The atomic level insight into the new catalyst activation principle based on metal vacancies is adaptable for developing other transition metal electrocatalysts, including Fe‐based ones.
Ultrathin feroxyhyte (δ‐FeOOH) nanosheets with rich Fe‐vacancies on Ni foam are synthesized, based on which an iron‐vacancy‐based catalyst activation principle to induce water‐splitting bifunctionality is proposed. Theoretical studies confirm that the formation of the second neighboring Fe to Fe vacancies in δ‐FeOOH nanosheets can create active centers for both hydrogen and oxygen evolution reactions.
Development of stimuli‐responsive materials with complex practical functions is significant for achieving bioinspired artificial intelligence. It is challenging to fabricate stimuli‐responsive ...hydrogels showing simultaneous changes in fluorescence color, brightness, and shape in response to a single stimulus. Herein, a bilayer hydrogel strategy is designed by utilizing an aggregation‐induced emission luminogen, tetra‐(4‐pyridylphenyl)ethylene (TPE‐4Py), to fabricate hydrogels with the above capabilities. Bilayer hydrogel actuators with the ionomer of poly(acrylamide‐r‐sodium 4‐styrenesulfonate) (PAS) as a matrix of both active and passive layers and TPE‐4Py as the core function element in the active layer are prepared. At acidic pH, the protonation of TPE‐4Py leads to fluorescence color and brightness changes of the actuators and the electrostatic interactions between the protonated TPE‐4Py and benzenesulfonate groups of the PAS chains in the active layer cause the actuators to deform. The proposed TPE‐4Py/PAS‐based bilayer hydrogel actuators with such responsiveness to stimulus provide insights in the design of intelligent systems and are highly attractive material candidates in the fields of 3D/4D printing, soft robots, and smart wearable devices.
Bioinspired hydrogels with abilities of simultaneous fluorescence color and brightness changes, as well as complex shape deformation under pH stimulus by utilizing aggregation‐induced emission luminogens (AIEgens) and the bilayer hydrogel technique are designed and fabricated.
Novel 3D Ni1−xCoxSe2 mesoporous nanosheet networks with tunable stoichiometry are successfully synthesized on Ni foam (Ni1−xCoxSe2 MNSN/NF with x ranging from 0 to 0.35). The collective effects of ...special morphological design and electronic structure engineering enable the integrated electrocatalyst to have very high activity for hydrogen evolution reaction (HER) and excellent stability in a wide pH range. Ni0.89Co0.11Se2 MNSN/NF is revealed to exhibit an overpotential (η10) of 85 mV at −10 mA cm−2 in alkaline medium (pH 14) and η10 of 52 mV in acidic solution (pH 0), which are the best among all selenide‐based electrocatalysts reported thus far. In particular, it is shown for the first time that the catalyst can work efficiently in neutral solution (pH 7) with a record η10 of 82 mV for all noble metal‐free electrocatalysts ever reported. Based on theoretical calculations, it is further verified that the advanced all‐pH HER activity of Ni0.89Co0.11Se2 is originated from the enhanced adsorption of both H+ and H2O induced by the substitutional doping of cobalt at an optimal level. It is believed that the present work provides a valuable route for the design and synthesis of inexpensive and efficient all‐pH HER electrocatalysts.
An integrated electrocatalyst comprising 3D mesoporous Ni0.89Co0.11Se2 nanosheet networks on Ni foam is synthesized, and it demonstrates very high activities and excellent stabilities for hydrogen evolution reaction (HER) in all‐pH conditions. Theoretical calculations verify that electronic structure engineering by optimal Co doping enhances the adsorption of H+ and H2O, leading to the advanced all‐pH HER activity of the catalyst.
The authors provide at a look at the biological applications of supramolecular assemblies that have been designed for excitation energy transfer. The topics discussed include biosensors and ...bioimaging.
The dynamic behavior of a macroscopic adhered hydrogel stabilized through controllable dynamic covalent interactions is reported. These interactions, involving the cross‐linked formation of a ...hydrogel through reaction of a diacylhydrazine precursor with a tetraformyl partner, increase as a function of time. By using a contact time of 24 h and different compounds with recognized aggregation‐induced emission features (AIEgens), it proves possible to create six laminated acylhydrazone hydrogels displaying different fluorescent colors. Blocks of these hydrogels are then adhered into a structure resembling a Rubik's Cube, a trademark of Rubik's Brand Limited, (RC) and allowed to anneal for 1 h. This produces a 3 × 3 × 3 block (RC) wherein the individual fluorescent gel blocks are loosely adhered to one another. As a consequence, the 1 × 3 × 3 layers making up the RC can be rotated either horizontally or vertically to produce new patterns. Ex situ modification of the RC or application of a chemical stimulus can be used to produce new color arrangements. The present RC structure highlights how the temporal features, strong versus weak adhesion, may be exploited to create smart macroscopic structures.
A hydrogel resembling a Rubik's Cube, a trademark of Rubik's Brand Limited, is made via controllable dynamic covalent interactions. Its layers can be rotated either horizontally or vertically to produce new patterns. Ex situ modification or a chemical stimulus can also produce new color arrangements. The creation of multiple patterns may allow for potential applications in patterns‐related material research.
An electrocatalytic methanol oxidation reaction (MOR) is proposed to replace oxygen evolution reaction (OER) in water electrolysis owing to the favorable thermodynamics of MOR than OER. However, ...there is still a competition between the MOR and the OER when the applied potential is in the conventional OER zone. How to inhibit OER while maintaining efficient MOR is an open and challenging question, and there are few reports focusing on this thus far. Herein, by taking NiFe layered double hydroxide (LDH) as a model catalyst due to its intrinsically high catalytic activity for the OER, the perspective of inhibiting OER is shown and thus promoting MOR through a heterogenous engineering of NiFe‐LDH. The engineered heterostructure comprising NiFe‐LDH and in situ formed NiFe‐hexylaminobenzene (NiFe‐HAB) coordination polymer exhibits outstanding electrocatalytic capability for methanol oxidation to formic acid (e.g., the Faradaic efficiencies (FEs) of formate product are close to 100% at various current densities, all of which are much larger than those (53–65%) on unmodified NiFe‐LDH). Mechanism studies unlock the modification of NiFe‐HAB passivates the OER activity of NiFe‐LDH through tailoring the free energies for element reaction steps of the OER and increasing the free energy of the rate‐determining step, consequently leading to efficient MOR.
The engineered novel heterostructure comprising NiFe‐LDH and in situ formed NiFe‐hexylaminobenzene (NiFe‐HAB) coordination polymer exhibits outstanding electrocatalytic capability for methanol oxidation to formic acid. Mechanism studies unlock the modification of NiFe‐HAB passivates the OER activity of NiFe‐LDH through tailoring the free energies for element reaction steps of the OER and increasing the free energy of the rate‐determining step.
Development of high‐performance and low‐cost nonprecious metal electrocatalysts is critical for eco‐friendly hydrogen production through electrolysis. Herein, a novel nanoflower‐like electrocatalyst ...comprising few‐layer nitrogen‐doped graphene‐encapsulated nickel–copper alloy directly on a porous nitrogen‐doped graphic carbon framework (denoted as Nix
Cuy
@ NG‐NC) is successfully synthesized using a facile and scalable method through calcinating the carbon, copper, and nickel hydroxy carbonate composite under inert atmosphere. The introduction of Cu can effectively modulate the morphologies and hydrogen evolution reaction (HER) performance. Moreover, the calcination temperature is an important factor to tune the thickness of graphene layers of the Nix
Cuy
@ NG‐NC composites and the associated electrocatalytic performance. Due to the collective effects including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and graphene shell, the Ni3Cu1@ NG‐NC electrocatalyst obtained under optimized conditions exhibits highly efficient and ultrastable activity toward HER in harsh environments, i.e., a low overpotential of 122 mV to achieve a current density of 10 mA cm−2 with a low Tafel slope of 84.2 mV dec−1 in alkaline media, and a low overpotential of 95 mV to achieve a current density of 10 mA cm−2 with a low Tafel slope of 77.1 mV dec−1 in acidic electrolyte.
A novel nanoflower‐like electrocatalyst comprising few‐layer nitrogen‐doped graphene‐encapsulated nickel–copper alloy on a porous nitrogen‐doped graphic carbon framework is synthesized by a facile and scalable method, and exhibits high activity and excellent stability for hydrogen evolution due to the collective effects, including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and the graphene shell.
Development of high‐performance and cost‐effective non‐noble metal electrocatalysts is pivotal for the eco‐friendly production of hydrogen through electrolysis and hydrogen energy applications. ...Herein, the synthesis of an unconventional nickel nitride nanostructure enriched with nitrogen vacancies (Ni3N1−x) through plasma‐enhanced nitridation of commercial Ni foam (NF) is reported. The self‐supported Ni3N1−x/NF electrode can deliver a hydrogen evolution reaction (HER) activity competitive to commercial Pt/C catalyst in alkaline condition (i.e., an overpotential of 55 mV at 10 mA cm−2 and a Tafel slope of 54 mV dec−1), which is much superior to the stoichiometric Ni3N, and is the best among all nitride‐based HER electrocatalysts in alkaline media reported thus far. Based on theoretical calculations, it is further verified that the presence of nitrogen vacancies effectively enhances the adsorption of water molecules and ameliorates the adsorption–desorption behavior of intermediately adsorbed hydrogen, which leads to an advanced HER activity of Ni3N1−x/NF.
A self‐supported electrocatalyst comprising nickel nitride nanostructure enriched with nitrogen vacancies on Ni foam is synthesized, and it exhibits superior performance for hydrogen evolution reaction (HER) in alkaline condition. Theoretical calculations verify that nitrogen vacancies facilitate the adsorption of H2O on Ni3N1−x and optimize the adsorption–desorption behavior of intermediately adsorbed hydrogen, leading to the advanced HER activity of the catalyst.
Geometric (Z)- and (E)-isomers play important but different roles in life and material science. The design of new (Z)-/(E)- isomers and study of their properties, behaviors, and interactions are ...crucially important in molecular engineering. However, difficulties with their separation and structure confirmation limit their structural diversity and functionality in scope. In the work described herein, we successfully synthesized pure isomers of ureidopyrimidinone-functionalized tetraphenylethenes ((Z)-TPE-UPy and (E)-TPE-UPy), featuring both the aggregation-induced emission characteristic of tetraphenylethene and the supramolecular polymerizability of ureidopyrimidinone. Their structures were confirmed by 2D COSY and NOESY NMR spectroscopies. The two isomers show distinct fluorescence in the aggregate state: (Z)-TPE-UPy exhibits green emission, while its (E)-counterpart is blue-emitting. The cavity formed by the two ureidopyrimidinone groups of (Z)-TPE-UPy makes it suitable for Hg2+ detection, and the high-molecular-weight polymers prepared from (E)-TPE-UPy can be used to fabricate highly fluorescent fibers and 2D/3D photopatterns from their chloroform solutions.
A novel mesoporous nanosheet networked hybrid comprising Co3O4 and Co3(PO4)2 is successfully synthesized using a facile and scalable method through calcinating the carbon, cobalt hydroxy carbonate, ...and cobalt phosphate composite precursor. Electron transfer from Co3O4 to Co3(PO4)2, together with the special networked structure and the porous nature of the nanosheets enable the Co3(PO4)2‐Co3O4 hybrid to have a high oxygen evolution reaction (OER) activity and outstanding stability in alkaline electrolyte, e.g., an overpotential of 270 mV at current density of 10 mA cm−2, and a Tafel slope of 39 mV dec−1, which are superior to most non‐noble metal‐based OER electrocatalysts reported thus far and as well the commercial RuO2 electrocatalyst. Furthermore, Co3(PO4)2‐Co3O4 hybrid is demonstrated to be used as an efficient cocatalyst to enhance the photoelectrochemical OER performance of BiVO4 photoanode. A significantly increased photocurrent density of 3.0 mA cm−2 at 1.23 V (vs reversible hydrogen electrode, RHE), and a potential reduction of 530 mV with respect to that of bare BiVO4 at the photocurrent density of 0.5 mA cm−2 are achieved. The electron transfer‐induced enhancement of OER by a hybrid structure may pave the new routes for the design and synthesis of low‐cost catalysts for electrochemical and photoelectrochemical oxygen evolution.
A novel networked mesoporous nanosheet hybrid composed of Co3O4 and Co3(PO4)2 is synthesized through calcinating the carbon, cobalt hydroxy carbonate, and cobalt phosphate composite precursor. Beneficial from the collective effects of special morphological design and the synergistic enhancement effect between ingredients, the Co3(PO4)2‐Co3O4 nanocomposite exhibits very high activities and excellent stabilities for the electrochemical and photoelectrochemical oxygen evolution reaction.
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