Biomass-Derived Anion-Anchoring Nano-CaCO3 Coating for Regulating Ion Transport on Li Metal Surface.

The free transport of anions in a Li metal battery can cause multiple issues, including a high anion transference number, space charge, and concentration polarization, eventually leading to uncontrolled dendrite formation and decreased performance. Herein, we report an anion-anchoring nano-CaCO3 (NC) coating derived from eggshell biowaste for stabilizing Li metal anodes. As the adsorption of local TFSI- anions onto the NC adsorbent can undermine the anion concentration gradient and promote rapid Li-ion diffusion, it can effectively inhibit the proliferation of Li dendrites assisted by the NC coating. Consequently, Li/Cu cells with NC@Cu electrode can achieve a high Coulombic efficiency of ∼98.4% for more than 420 cycles and can even reach ∼99.1% at an ultrahigh areal capacity of 20 mAh cm-2. In particular, full cells with NC/Li@Cu electrodes show a stable lifespan of over 240 cycles with an average efficiency of ∼99.8% at a low N/P ratio of ∼3.3.

Synthesis of NiSe2 /Fe3 O4 Nanotubes with Heteroepitaxy Configuration as a High-Efficient Oxygen Evolution Electrocatalyst.

The rational design of high-efficient non-noble metal electrocatalysts for oxygen evolution reactions (OER) is of significance in electrochemical energy conversion. However, such low-cost but highly active electrocatalysts remain poorly developed because of the daunting synthetic challenge. Here, the synthesis of NiSe2 /Fe3 O4 nanotubes via a facile self-templating strategy, which manifests unique tetragonal morphology, asymmetric hollow interior, and unusual but adaptable heteroepitaxy structure, is reported. Benefiting from sufficient active sites and their improved activity around the heterointerface, accompanied by the good conductivity, the NiSe2 /Fe3 O4 nanotubes exhibit as a superior OER electrocatalyst, which affords the current density of 10 mA cm-2 at a very small overpotential of 199 mV, high attainable current density beyond 200 mA cm-2 , and mass activity of 984.5 A g-1 , as well as excellent stability for 100 h in the alkaline media. This work provides a unique synthetic pathway to fabricate superior OER electrocatalysts by optimizing their composition and architecture.

Atomically Dispersed Cu Sites on Dual-Mesoporous N-Doped Carbon for Efficient Ammonia Electrosynthesis from Nitrate.

The industrial Haber-Bosch process for ammonia synthesis is extremely important in modern society. However, it is energy intensive and leads to severe pollution, which has motivated eco-friendly NH3 synthesis research. Electroreduction of contaminant nitrate ions back to NH3 is an effective complement but is still limited by low NH3 yields and nitrate-to-NH3 selectivities. In this study, the electrochemical nitrate reduction reaction (NTRR) is carried out over a single-atom Cu catalyst. Atomically dispersed Cu sites anchored on dual-mesoporous N-doped carbon framework display excellent NTRR performance with NH3 production rate of 13.8 mol NH 3 gcat -1 h-1 and NO3 - -to-NH3 faradaic efficiency (FE) of 95.5 % at -1.0 V. Cu-N-C catalyst can sustain continuous 120 h NTRR test in the simulated NH3 synthesis scenarios with large current density (about 200 mA cm-2 ) and amplified volume of NO3 - solution (9 times). Theoretical calculations reveal that atomically dispersed Cu1 -N4 sites reduce the energy barrier of potential-determining step in NTRR and promote the decomposition of primary intermediate in NO3 - -to-N2 process. These findings provide a guideline for the rational design of highly active, selective and durable electrocatalysts for the NTRR.

Construction of Ni(CN)2 /NiSe2 Heterostructures by Stepwise Topochemical Pathways for Efficient Electrocatalytic Oxygen Evolution.

Exploiting effective electrocatalysts based on elaborate heterostructures for the oxygen evolution reaction (OER) has been considered as a promising strategy for boosting water splitting efficiency to produce the clean energy-hydrogen. However, constructing catalytically active heterostructures with novel composition and architecture remains poorly developed due to the synthetic challenge. In this work, it is demonstrated that unique Ni(CN)2 /NiSe2 heterostructures, composed of single-crystalline Ni(CN)2 nanoplates surrounded by crystallographically aligned NiSe2 nanosatellites, can be created from nickel-based Hofmann-type coordination polymers through stepwise topochemical pathways. When employed as the OER electrocatalyst, the Ni(CN)2 /NiSe2 heterostructures show enhanced performance, which could be attributed to optimized geometric and electronic structures of the catalytic sites endowed by the synergy between the two components. This work demonstrates a rational synthetic route for creating a novel Ni-based OER electrocatalyst that possesses nanoscale heterostructure, whose composition, spatial organization, and interface configuration can be finely manipulated.

Moldable Hyaluronan Hydrogel Enabled by Dynamic Metal-Bisphosphonate Coordination Chemistry for Wound Healing.

Biomaterial-based regenerative approaches would allow for cost-effective off-the-shelf solution for the treatment of wounds. Hyaluronan (HA)-based hydrogel is one attractive biomaterial candidate because it is involved in natural healing processes, including inflammation, granulation, and reepithelialization. Herein, dynamic metal-ligand coordination bonds are used to fabricate moldable supramolecular HA hydrogels with self-healing properties. To achieve reversible crosslinking of HA chains, the biopolymer is modified with pendant bisphosphonate (BP) ligands using carbodiimide coupling and chemoselective "click" reactions. Hydrogel is formed immediately after simple addition of silver (Ag+ ) ions to the solution of HA containing BP groups (HA-BP). Compared with previous HA-based wound healing hydrogels, the HA-BP·Ag+ hydrogel is highly suitable for clinical use as it can fill irregularly shaped wound defects without the need for premolding. The HA-BP·Ag+ hydrogel shows antimicrobial properties to both Gram-positive and Gram-negative bacterial strains, enabling prevention of infections in wound care. In vivo evaluation using a rat full-thickness skin wound model shows significantly lower wound remaining rate and a thicker layer of regenerated epidermis as compared with the group left without treatment. The presented moldable and self-healing supramolecular HA hydrogel with "ready-to-use" properties possesses a great potential for regenerative wound treatment.

Preparation of a novel silk microfiber covered by AgCl nanoparticles with antimicrobial activity.

We prepared silk fibroin microfibers in which silver chloride (AgCl) nanoparticles were dispersed, by sequential dipping of microfibers obtained using alkaline hydrolysis in alternating solutions of silver nitrate and potassium chloride. Scanning and transmission electron microscopy showed an increase in nanoparticle size and quantity with increase in dipping cycles and solution concentration, but ultrasound irradiation did not affect nanoparticle formation. The presence of cubic AgCl crystals was confirmed by energy dispersive X-ray spectroscopy and X-ray diffractometry. Differential scanning calorimetry and Fourier transform infrared spectroscopy revealed that the nanoparticles do not affect the microfiber properties. The growth of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria was inhibited by microfiber covered with AgCl nanoparticles. This antimicrobial activity allows to use microfiber as a reinforced or surface additive biomaterial. Microsc. Res. Tech. 80:272-279, 2017. © 2016 Wiley Periodicals, Inc.