For efficient removal of intra- and/or extracellular hydrogen peroxide by dismutation to harmless dioxygen and water (2H(2)O(2) → O(2) + 2H(2)O), nature designed three metalloenzyme families that differ in oligomeric organization, monomer architecture as well as active site geometry and catalytic residues. Here we report on the updated reconstruction of the molecular phylogeny of these three ge...

Blowing bubbles: Hydrogen evolution by proton reduction with [(C(5)Me(5))(2)Fe] occurs at a soft interface between water and 1,2-dichloroethane (DCE). The reaction proceeds by proton transfer assisted by [(C(5)Me(5))(2)Fe] across the water-DCE interface with subsequent proton reduction in DCE. The interface essentially acts as a proton pump, allowing hydrogen evolution by directly using the aqu...

Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high barriers. Information about the energy landscape for H2 production can be obtained by chemical characterization of catalytic intermediates, but few have been observed to date. We have isolated and characterized a key intermediate in 2e(-) + 2H(+) → H2 catalysis. This interm...

Warm Neptuneand sub-Neptune-sized exoplanets in orbits smaller than Mercury’s are thought to have experienced extensive atmospheric evolution. Here we propose that a potential outcome of this atmospheric evolution is the formation of helium-dominated atmospheres. The hydrodynamic escape rates of Neptuneand subNeptune-sized exoplanets are comparable to the diffusion-limited escape rate of hydrog...

Spinach chloroplast preparations were mixed with Clostridium kluyveri hydrogenase and ferredoxin. Hydrogen evolution could be measured in the light in the absence of any added electron donors. Inhibition of the water-splitting reaction or of photosystem II reduced the amount of H(2) evolved more than 95%, indicating that H(2)O was the electron donor in this reaction. The rates of H(2) evolution...

Understanding the competition between hydrogen evolution and CO2 reduction is of fundamental importance to increase the faradaic efficiency for electrocatalytic CO2 reduction in aqueous electrolytes. Here, by using a copper rotating disc electrode, we find that the major hydrogen evolution pathway competing with CO2 reduction is water reduction, even in a relatively acidic electrolyte (pH 2.5)....

This study was conducted to determine some physiological conditions which influence light-in­ duced hydrogen evolution by intact cells of the blue-green alga Nostoc muscorum. This activity was found to be dependent on the age of the culture, cultivation temperature, ageing of the cells, and on gassing the cultures with nitrogen or air. Nitrogenase is particularly ac­ tive after cultivation at 2...

By combining density functional molecular dynamics simulations with a thermodynamic integration technique, we determine the free energy of metallic hydrogen and silica, SiO2, at megabar pressure and thousands of degrees Kelvin. Our ab initio solubility calculations show that silica dissolves into fluid hydrogen above 5000 K for pressures from 10 and 40 megabars, which has implication for the ev...

Reduced size and direct electrochemical H2 compression are two distinct advantages of electrolyzers based on the acid-polymer electrolyte membrane technology over those relying on alkaline electrolytes. However, recourse to catalysts based on the scarce platinum-group-metals has hitherto been the price to pay. While the transition metal sulfides and nitrides of group VI have recently shown inte...