Self-healing hydrogels have a great potential application in 3D printing, soft robotics, and tissue engineering. There have been a large number of successful strategies for developing hydrogels that exhibit rapid and autonomous recovery. However, developing a gel with an excellent self-healing performance within several seconds is still an enormous challenge. Here, an ultrafast self-healing hydrogel based on an agarose/PVA double network (DN) is presented. The gel utilizing a dynamic borate bond exhibits 100% cure in strength and elongation after healing for 10 s in air, and this hydrogel shows an excellent self-healing property underwater as well. In addition, the agarose/PVA DN hydrogel exhibits a smart self-healing property for an in situ priority recovery, ensuring that the shape and the function are the same as those of the original one. With the combination of self-healing properties, such a hydrogel could be applied to a board range of areas.
Molecular-scale modulation of interfaces between different unilamellar nanosheets in superlattices is promising for efficient catalytic activities. Here, three kinds of superlattices from alternate restacking of any two of the three unilamellar nanosheets of MoS 2 , NiFe-layered double hydroxide (NiFe-LDH), and graphene are systematically investigated for electrocatalytic water splitting. The MoS 2 /NiFe-LDH superlattice exhibits a low overpotential of 210 and 110 mV at 10 mA cm −2 for oxygen evolution reaction (OER) and alkaline hydrogen evolution reaction (HER), respectively, superior than MoS 2 / graphene and NiFe-LDH/graphene superlattices. High activity and stability toward the overall water splitting are also demonstrated on the MoS 2 /NiFe-LDH superlattice bifunctional electrocatalyst, outperforming the commercial Pt/C-RuO 2 couple. This outstanding performance can be attributed to optimal adsorption energies of both HER and OER intermediates on the MoS 2 /NiFe-LDH superlattice, which originates from a strong electronic coupling effect at the heterointerfaces. These results herald the interface modulation of superlattices providing a promising approach for designing advanced electrocatalysts.
Electrocatalytic denitrification is a promising technology for removing NOx species (NO3−, NO2− and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of *NO versus *H. Analogous to classifying CO2 reduction by *CO vs. *H, Cu is able to bind *NO while not binding *H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity‐volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2‐to‐CO. At potential above 0.3 V vs. RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provides a clear strategy for selectivity and aims to inspire future research on NOxRR.
Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Insufficient catalytic activity and stability and high cost are the barriers for Pt‐based electrocatalysts in wide practical applications. Herein, a hierarchically porous PtNi nanoframe/N‐doped graphene aerogel (PtNiNF‐NGA) electrocatalyst with outstanding performance toward methanol oxidation reaction (MOR) in acid electrolyte has been developed via facile tert‐butanol‐assisted structure reconfiguration. The ensemble of high‐alloying‐degree‐modulated electronic structure and correspondingly the optimum MOR reaction pathway, the structure superiorities of hierarchical porosity, thin edges, Pt‐rich corners, and the anchoring effect of the NGA, endow the PtNiNF‐NGA with both prominent electrocatalytic activity and stability. The mass and specific activity (1647 mA mgPt−1, 3.8 mA cm−2) of the PtNiNF‐NGA are 5.8 and 7.8 times higher than those of commercial Pt/C. It exhibits exceptional stability under a 5‐hour chronoamperometry test and 2200‐cycle cyclic voltammetry scanning.
In the past decade, the mass activity
of catalysts for the oxygen
reduction reaction (ORR) has been improved mainly via increasing the
number of active sites. However, little progress has been made on
the improvement of the intrinsic activity of ORR catalysts; consequently,
the widespread use of fuel cells is still limited by low energy efficiency.
In this Perspective, we provide an overview of the fundamentals underlying
the ORR on platinum-based catalysts as well as metal–nitrogen–carbon
nonprecious metal catalysts. We also report the diporphyrin complexes
as promising catalysts with outstanding activity owing to structural
advantages. In particular, diporphyrin anthracene (DPA) with optimized
ligand coordination has a low barrier to dissociate O2 molecules
at the optimal oxygen adsorption energy region, which might unlock
overpotentials of less than 0.2 V.
A major contribution to the energy loss in fuel cells originates from poor kinetics of the oxygen reduction reaction (ORR) at the cathode. The ORR mechanism has been understood in descriptor-based approaches, which reveal an activity volcano with a significant overpotential of at least 0.4 V. This energy loss is directly linked to the scaling relation between the binding energy of the ORR intermediates, OH and the OOH. It has become apparent that new catalyst designs are necessary in order to circumvent this scaling relation. One strategy is to stabilize the OOH intermediate in a dissociated state on two active sites, as an O + OH intermediate. Here we demonstrate the feasibility of this strategy in a systematic study of diporphyrin molecular catalysts. This class of catalysts contains two metal sites, whose catalytic chemistry can be influenced by ligands. Using density functional theory (DFT), we study the ORR activity as a function of intermetallic distance, metals, and ligands. Several diporphyrin catalysts are identified with a theoretical overpotenial of less than 0.3 V. The enhanced catalytic activity is understood as a combination of a geometric effect from the diporphyrin structure and an electronic effect from the choice of metal center and ligand. We propose a strategy to reduce the energy loss and climb the 3D volcano by appropriate design of the geometric and the electronic effects.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.