Anoxic photogeochemical oxidation of manganese carbonate yields manganese oxide.

ABSTRACT: The oxidation states of manganese minerals in the geological record have been interpreted as proxies for the evolution of molecular oxygen in the Archean eon. Here we report that an Archean manganese mineral, rhodochrosite (MnCO₃), can be photochemically oxidized by light under anoxic, abiotic conditions. Rhodochrosite has a calculated bandgap of about 5.4 eV, corresponding to light energy centering around 230 nm. Light at that wavelength would have been present on Earth's surface in the Archean, prior to the formation of stratospheric ozone. We show experimentally that the photooxidation of rhodochrosite in suspension with light centered at 230 nm produced H₂ gas and manganite (γ-MnOOH) with an apparent quantum yield of 1.37 × 10^-3 moles hydrogen per moles

SUBMITTER: Liu W 

PROVIDER: S-EPMC7502741 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature