Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to ...fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.
The electrochemical reduction of CO2 could play an important role in addressing climate-change issues and global energy demands as part of a carbon-neutral energy cycle. Single-atom catalysts can ...display outstanding electrocatalytic performance; however, given their single-site nature they are usually only amenable to reactions that involve single molecules. For processes that involve multiple molecules, improved catalytic properties could be achieved through the development of atomically dispersed catalysts with higher complexities. Here we report a catalyst that features two adjacent copper atoms, which we call an ‘atom-pair catalyst’, that work together to carry out the critical bimolecular step in CO2 reduction. The atom-pair catalyst features stable Cu10–Cu1x+ pair structures, with Cu1x+ adsorbing H2O and the neighbouring Cu10 adsorbing CO2, which thereby promotes CO2 activation. This results in a Faradaic efficiency for CO generation above 92%, with the competing hydrogen evolution reaction almost completely suppressed. Experimental characterization and density functional theory revealed that the adsorption configuration reduces the activation energy, which generates high selectivity, activity and stability under relatively low potentials.Anchored single-atom catalysts have recently been shown to be very active for various processes, however, a catalyst that features two adjacent copper atoms—which we call an atom-pair catalyst—is now reported. The Cu10–Cu1x+ pair structures work together to carry out the critical bimolecular step in CO2 reduction.
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.
A solid electrolyte interphase (SEI) plays an essential role in the functionality and service life of ion batteries, where the structure and formation mechanism are still in the midst. Here, we ...investigate the initial decomposition and reactions of ethylene carbonate (EC) on the surface of a graphite anode using first-principles calculations. EC initially decomposes via the homolytic ring opening with the product of radical anion CH2CH2OCO2−. Bonding with Li, it forms a co-plane structure of CH2CH2OCO2Li, with a binding energy of 1.35 eV. The adsorption energy is −0.91 eV and −0.24 eV on the graphite zigzag edge surface and basal surface, respectively. Two CH2CH2OCO2Li molecules react to form a two-head structure of lithium ethylene dicarbonate (CH2OCO2Li)2, namely LEDC, which further forms a network preferring zigzag edge surfaces. Our results suggest that the first and innermost layers of the solid electrolyte interphase are CH2CH2OCO2Li sticking and networking on the zigzag edges of the surfaces of graphite anodes.
We have succeeded in synthesizing Co3O4 nanosheets, nanobelts, and nanocubes with a hydrothermal process of cobalt hydroxide precursor and subsequent direct thermal decomposition. The predominantly ...exposed planes are {112}, {011}, and {001}, respectively. The methane combustion catalytic activity order of crystal planes follows {112} > {011} ≫ {001}. The selective synthesis of transition metal oxides with uniform and different reactive crystal planes under nanoscale conditions is expected to bring up new opportunities for design, tuning, and control of chemical activity, specificity, and selectivity.
A facile approach for the preparation of supramolecular polymer‐based fluorescent nanoparticles (FNPs) is reported. FNPs with homogeneous shape and size distribution are fabricated from ...low‐molecular‐weight molecules, and thus, different compositional constituents can be efficiently incorporated via copolymerization. The emission color of the FNPs covers a wide region from blue to near infrared and can be easily tuned using efficient excitation energy transfer. The photoswitchable fluorescent nanoparticles with high on–off fluorescence contrast are also simply prepared by copolymerization of monomers containing a fluorophore and a photochromic unit. Our FNPs are successfully applied in living cell imaging and as fluorescent inks.
A new set of fluorescent nanoparticles (FNPs) are fabricated from hydrogen‐bonded supramolecular polymers. Their preparation is straightforward, and nanoparticles with homogeneous shape and size are obtained. The emission color of the FNPs covers a wide region from blue to near infrared and is easily tunable by excitation energy transfer. These FNPs are successfully used in bioimaging and as fluorescent inks.
The performance and the cost of electrocatalysts play the two most vital roles in the development and application of energy conversion technologies. Single-atom catalysts (SACs) are recently emerging ...as a new frontier in catalysis science. With maximum atom-utilization efficiency and unique properties, SACs exhibit great potential for enabling reasonable use of metal resources and achieving atomic economy. However, fabricating SACs and maintaining the metal centers as atomically dispersed sites under synthesis and catalysis conditions are challenging. Here, we highlight and summarize recent advances in wet-chemistry synthetic methods for SACs with special emphasis on how to achieve the stabilization of single metal atoms against migration and agglomeration. Moreover, we summarize and discuss the electrochemical applications of SACs with a focus on the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and CO2 reduction reaction (CO2RR). At last, the current issues and the prospects for the development of this field are discussed.
Display omitted
The development of synthetic strategies plays a fundamental role in advancing catalysis science and practical application of single-atom catalysts (SACs). Owing to the high surface energy of single atoms, achieving the atomic dispersion of mononuclear metal precursors and stabilizing the as-formed single atoms against migration and agglomeration are key aspects in the synthesis of SACs. Several innovative synthetic strategies for SACs are summarized and highlighted through discussion of recent advances in the synthesis of SACs via wet-chemistry approaches.
Furthermore, the great potential of SACs in electrochemical applications, with special emphasis on key clean energy conversion reactions including the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and CO2 reduction reaction (CO2RR), are presented and discussed. Further research on single-atom catalysis should focus on understanding the structure-performance relationship and catalytic mechanism at the atomic scale by employing SACs as model systems with the aid of theoretical calculation and in situ characterization technologies to achieve an atomic-economic green catalytic process.
Developing single-atom catalysts (SACs) plays a fundamental role in advancing catalysis science and practical application. Owing to high surface energy, fabricating SACs remains a great challenge. In this review, we not only summarize recent advances on wet-chemistry methods and discuss the key points for the synthesis of SACs, but also highlight the potential applications of SACs for clean energy conversion reactions.
The first example of a ratiometric optical oxygen nanoprobe based on a hydrogen‐bonded supramolecular polymer has been reported. The supramolecular polymer based nanoprobe (SPNP) is prepared from the ...co‐assembly of a bis‐ureidopyrimidinone (bis‐UPy)‐containing phosphorescent indicator (Por(Pd)‐bisUPy), fluorescent reference dye (BF2‐bisUPy), and skeleton unit (DPA‐bisUPy) through quadruple hydrogen bonds by a mini‐emulsion method. The water‐dispersible SPNP is highly sensitive to oxygen (Q = 95%), with full reversibility, excellent storage stability and photostability, and good cell‐penetrating ability, and exhibits low cytotoxicity toward living cells. The preparation of the SPNP is straightforward and its function is easily tuned by changing the monomeric structure. This work is expected to lead to the design of other SPNPs for other important analytes in biological systems.
The first water‐dispersible supramolecular‐polymer‐based ratiometric oxygen nanoprobe (SPNP) is reported. The preparation of the SPNP is straightforward and its function is easily tuned by changing the monomeric structures. The SPNP is highly sensitive to oxygen, with full reversibility, excellent storage stability and photostability, and good cell‐penetrating ability, and exhibit low cytotoxicity toward living cells.
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.
PDF
