A fluorine-doped tin oxide-coated glass electrode modified with a bilayer film of underlying α-Co­(OH)2 and overlying Mg-intercalated and Co-doped δ-type (layered) MnO2 (Mg|Co-MnO2) preferentially yielded oxygen with a Faradaic efficiency as high as 79% in the presence of chloride ions at high concentration (0.5 M). This noble metal-free electrode was fabricated by cathodic electrolysis of aqueous Co­(NO3)2 followed by anodic electrolysis of a mixture of Mn2+, Co2+, and cetyltrimethylammonium (CTA+) ions in water. The CTA+ ions accommodated in the interlayer spaces of Co-doped δ-MnO2 were replaced with Mg2+ by ion exchange. The upper Mg|Co-MnO2 could effectively block the permeation of Cl– ions and allow only H2O and O2, while the under α-Co­(OH)2 acted as an oxidation catalyst for the H2O penetrated through the upper coating. Thus, the oxygen evolution reaction (OER) was preferred to the chlorine evolution reaction (CER). In artificial seawater (pH 8.3), the blocking effect against Cl– decreased because of ion exchange of the intercalated Mg2+ ions with Na+ in solution, but the OER efficiency still remained at 57%, much higher than that (28%) without the upper Mg|Co-MnO2. This demonstrates that the interlayer spaces between MnO2 layers acted as pathways for H2O molecules to reach the active sites of the underlying Co­(OH)2. Density functional theory (DFT) calculations revealed that the most stable structure of hydrated Mg2+ ion, in which a part of coordinated H2O molecules is hydrolyzed, has less affinity toward Cl– ion than that of hydrated Na+ ion.

Graphical abstractNew cationic heteroleptic Ln(III) complexes with acetylacetonate and bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)propane basis are synthesized. The complexes are characterized by various means, including single crystal X-ray diffraction analysis. Electronic absorption and emission spectra of the compounds both in solid and solutions are studied.

Luminescent helical lanthanide complexes with hydrophilicity were examined for stability and reversibility in a pH region between 1.9 and 11.9.

Paraffin coatings on glass slides were investigated through both X-ray photoelectron spectroscopy (XPS) and spin relaxation measurement for cesium (Cs) vapor. The components of the glass substrate, such as silicon and oxygen, existed in the XPS spectra of the coated slides, indicating the imperfection of the prepared paraffin coatings. The substrate was not observed after the annealing of the coatings in Cs vapor, which is known as a "ripening" process for spin relaxation measurement. We found a general trend that effective anti-spin relaxation performance requires high paraffin and low Cs coverage on the surface. We also examined a type of diamond-like carbon film, anticipating the effect of anti-spin relaxation; our attempts have failed to date.

The purpose of this study is to propose a new strategy based on electrodeposition to create binder-free composites of metallic silver supported on MnO 2 . The process involves in situ reduction of the Ag + ions incorporated in the interlayer spaces of layered MnO 2 in an alkaline electrolyte without Ag + ions. The reduction process of the incorporated Ag + was monitored in situ based on the characteristic surface plasmon resonance in the visible region, and the resulting metallic Ag was identified by X-ray photoelectron spectroscopy. Because the formation of metallic Ag is only possible via electron injection into the Ag + ions between MnO 2 layers, the growth of Ag metals was inevitably limited, although the reduced Ag did not remain immobilized in the interlayers of MnO 2 . The thus-formed Ag in the MnO 2 composite functioned as an electrocatalyst for the oxygen reduction reaction in a gas diffusion electrode system, showing a much better mass activity compared to Ag particles electrodeposited from an aqueous solution containing AgNO 3 .