Surface Engineering Stabilizes Rhombohedral Sodium Manganese Hexacyanoferrates for High-Energy Na-Ion Batteries

The rhombohedral sodium manganese hexacyanoferrate (MnHCF) only containing cheap Fe and Mn metals was regarded as a scalable, low-cost, and high-energy cathode material for Na-ion batteries. However, the unexpected Jahn-teller effect and significant phase transformation would cause Mn dissolution and anisotropic volume change, thus leading to capacity loss and structural instability. Here we report a simple room-temperature route to construct a magical Co_xB skin on the surface of MnHCF. Benefited from the complete coverage and the buffer effect of Co_xB layer, the modified MnHCF cathode exhibits suppressed Mn dissolution and reduced intergranular cracks inside particles, thereby demonstrating thousands-cycle level cycling lifespan. By comparing two key parameters in the real energy world, i.e., cost per kilowatt-hours and cost per cycle-life, our developed Co_xB coated MnHCF cathode demonstrates more competitive application potential than the benchmarking LiFePO₄ for Li-ion batteries.     

Non-soluble chalcones and their potential application as corrosion coatings on carbon steel exposed to 1 M HCl solutions

Chalcones are secondary metabolites of great interest in chemistry due to their broad biological activities. In recent years, the versatility of this class of molecules has been demonstrated, especially in several synthetic analogs, which have shown behavior as corrosion inhibitors. In this article, a series of chalcone analogs were synthesized using the Claisen-Schmidt methodology in both conventional and microwave-assisted irradiation methodologies. The obtained compounds are non-soluble, which widens the window of chalcones with the possibility of being used as anticorrosive. These were analyzed by electrochemical impedance spectroscopy, potentiodynamic polarization, weight loss measurements and scanning electron microscopy. The results suggest that the chalcone compounds such as the trans-4-(N,N-diphenylamino)chalcone (CH11), (E)-1-phenyl-3-(thiophen-2-yl)prop-2-en-1-one (CH15) and (E)-1-phenyl-3-(thiophen-3-yl)prop-2-en-1-one (CH16) have anticorrosive activity for carbon steel in HCl solutions. The electrochemical techniques showed that increasing the mass of the three chalcone on carbon steel increases the efficiency of the inhibition. A mass amount of 1.4 mg of CH15 or CH16 was shown to have the maximum inhibition from corrosion, but for CH11 the maximum inhibition was 3.0 mg on carbon steel. The percentage inhibition that reached these three compounds was about 95 % at 20 °C. Theoretical calculations by Density Functional Theory (DFT) were performed to explain the measured corrosion decrease assisted by compounds CH11, CH15, and CH16.