Stabilization of the cubic, fast-ion conducting phase of Li7La3Sn2O12 garnet by gallium doping.

All-solid-state batteries present promising high-energy-density alternatives to conventional Li-ion chemistries, and Li-stuffed garnets based on Li7La3Zr2O12 (LLZO) remain a forerunner for candidate solid-electrolytes. One route to access fast-ion conduction in LLZO phases is to stabilize the cubic LLZO phase by doping on the Li sites with aliovalent ions such as Al3+ or Ga3+. Despite prior attempts, the stabilization of the cubic phase of isostructural Li7La3Sn2O12 (LLSO) by doping on the Li sites has up to now not been realised. Here, we report a novel cubic fast-ion conducting Li7La3Sn2O12-type phase stabilized by doping Ga3+ in place of Li. 0.3 mole of gallium per formula unit of LLSO were needed to fully stabilize the cubic garnet, allowing structural and electrochemical characterizations of the new material. A modified sol-gel synthesis approach is introduced in this study to realise Ga-doping in LLSO, which offers a viable route to preparing new Sn-based candidate solid-electrolytes for all-solid-state battery applications.

Experimental and computational chemical studies on the corrosion inhibitive properties of carbonitrile compounds for carbon steel in aqueous solutions.

The present work aims to study 6-amino-4-aryl-2-oxo-1-phenyl-1,2-dihydropyridine-3,5-dicarbonitrile derivatives namely: 6-Amino-2-oxo-1,4-diphenyl-1,2-dihydropyridine-3,5-dicarbonitrile (PdC-H), 6-Amino-2-oxo-1-phenyl-4-(p-tolyl)-1,2-dihydropyridine-3,5-dicarbonitrile (PdC-Me) and 6-Amino-4-(4-hydroxyphenyl)-2-oxo-1-phenyl-1,2-dihydropyridine-3,5-dicarbonitrile (PdC-OH) as corrosion inhibitors to provide protection for carbon steel in a molar hydrochloric acid medium. Chemical measurements such as (weight loss) and electrochemical techniques such as (Potentiodynamic polarization, electrochemical impedance spectroscopy, and Electron frequency modulation) were applied to characterize the inhibitory properties of the synthesized derivatives. The adsorption of these derivatives on the carbon steel surface was confirmed by Attenuated Total Refraction Infrared (ATR-IR), Atomic Force Microscope (AFM), and X-ray Photoelectron Spectroscopy (XPS). Our findings revealed that the tested derivatives have corrosion inhibition power, which increased significantly from 75.7 to 91.67% on the addition of KI (PdC-OH:KI = 1:1) to inhibited test solution with PdC-OH derivative at 25 °C. The adsorption process on the metal surface follows the Langmuir adsorption model. XPS analysis showed that the inhibitor layer consists of an iron oxide/hydroxide mixture in which the inhibitor molecules are incorporated. Computational chemical theories such as DFT calculations and Mont Carlo simulation have been performed to correlate the molecular properties of the investigated inhibitors with experimental efficiency. The theoretical speculation by Dmol3 corroborates with the results from the experimental findings.