Ionization Potential of the OH Free Radical by Mass Spectrometry

Fabrication of Robust Hydrogen Evolution Reaction Electrocatalyst Using Ag2Se by Vacuum Evaporation

Much research has been done on reliable and low-cost electrocatalysts for hydrogen generation by water splitting. In this study, we synthesized thin films of silver selenide (Ag₂Se) using a simple thermal evaporation route and demonstrated their electrocatalytic hydrogen evolution reaction (HER) activity. The Ag₂Se catalysts show improved electrochemical surface area and good HER electrocatalytic behavior (367 mV overpotential @ 10 mA·cm⁻², exchange current density: ~1.02 × 10⁻³ mA·cm⁻², and Tafel slope: 53 mV·dec⁻¹) in an acidic medium). The reliability was checked in 0.5 M sulfuric acid over 20 h. Our first-principles calculations show the optimal energy of hydrogen adsorption, which is consistent with experimental results. The works could be further extended for finding a new catalyst by associating the selenide, sulfide or telluride-based materials without complex catalyst synthesis procedures.

Christopher Foote's discovery of the role of singlet oxygen [1O2 (1Delta g)] in photosensitized oxidation reactions

The chemistry of singlet molecular oxygen [1O2 (1Delta g)], its importance in atmospheric, biological, and therapeutic processes, and its use as a reagent in organic synthesis have been of considerable interest. Many aspects of singlet oxygen chemistry have emanated from the work of Christopher S. Foote and co-workers. Singlet oxygen is a historically interesting molecule with an unusual story connected with its discovery. Foote and Wexler conducted experiments in the 1960s where evidence was obtained supporting 1O2 generation via two independent routes: (1) a photochemical reaction (dye-sensitized photooxidation) and (2) a chemical reaction (NaOCl with H2O2). An important factor in the discovery of 1O2 as the critical reaction intermediate in dye-sensitized photooxygenations was Foote's reassessment of the chemical literature of the 1930s, when 1O2 was suggested to be a viable intermediate in dye-sensitized photooxidation reactions. Experiments that used silica gel beads provided evidence for a volatile diffusible oxidant such as 1O2. However, a contemporaneous quarrel surrounded this early work, and the possible existence of solution-phase 1O2 was ignored for over 2 decades. Not long after Foote's initial studies were published in 1964, the idea of singlet oxygen as an intermediate in photooxidation chemistry gained increasing recognition and verification in organic, gas phase, and biological processes. There are many documented impacts that 1O2 has had and continues to have on biology and medicine, for example, photodynamic therapy and plant defenses.

A MASS SPECTROMETRIC STUDY OF NORMAL OXYGEN AND OXYGEN SUBJECTED TO ELECTRICAL DISCHARGE

A mass spectrometric study was made of oxygen activated by microwave and by a-c. glow discharge. Appearance potential curves for normal oxygen at masses 16 and 32 indicated the occurrence of multiple electron impact processes. The change in the curves when the oxygen was activated could be interpreted by assuming the presence of O-atoms in the 3P ground state, and O2 molecules in the 1Δg excited state. No evidence was obtained for the presence of ozone up to pressures of 2 mm. Hg. The recombination coefficient of O-atoms on pyrex was found to be 1.1 × 10−4. Only one oxygen atom in 21 was ionized before recombining in the mass spectrometer ion source. The rate constant for the reaction of O-atoms with N2O is less than 1 × 10−8 cm.3 mole−1 sec.−1, and several orders of magnitude less than this for the reaction O(3P) + N2O → 2NO. The reaction of O-atoms with NO2 was much faster than with NO, but no evidence was found for the formation of NO3.